TRANSMISSION LINE MANUAL Publication No. 268
Central Board of Irrigation and Power Malcha Marg, Chanakyapuri, New Delhi - 110 021
CBI&P Panel of Experts on Transmission Lines Editor
'.J. Varma
Chairman D
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CENTRAL BOARD OF IRRIGATION AND POWER Esrablished 1\127
OBJECTIVES • To render expertise in the fields of water resources and energy; • To promote research and professional excellence; • To provide research linkages to Indian engineers, researchers and managers with their cOWlterparts in other countries andintemational organisations; • To establish database of technical and technological developments, and provide information services; • Teclmological forecasting.
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Research project reports. * Journals. * Design,constructioo and management pUblications. • Specifications/manuals/guidelines, • Conference proceedings. • Specific case studies. 4. Research
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Identifying research needs, sponsoring research projects. and monitoring R&D activities. * Assisting in specific case studies/problems. * Documentation.
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TRANSMISSION LINE MANUAL Publication No. 268
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S. lO
Editors C.V.J. Varma P.K. Lal
CBI&P Panel of Experts on Transmission Lines P.M. Ahluwalia Chainnan
CENTRAL BOARD OF IRRIGATION AND POWER Malcha Marg, Chanakyapuri, New Delhi 110 021
STANDING PANEL OF EXPERTS ON TRANSMISSION LINES Chairman
P.M. Ahluwalia Ex-Member, CEA
Members
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1.
Y.N. Rikh Ex-Chainnan, UPSEB
7.
Executi ve Director/Chief Engineer (Trans. Design), UPSEB
2.
V.D. Anand Ex -Chief Engineer, CEA
8.
Executive Director/Chief Engineer Transmission Designs, MPEB
3.
M.L. Sachdeva Ex-Chief Engineer, CEA
9.
Executi ve Director/Chief Engineer Transmission Design, GEB
4.
Chief EngineerlDirector (Trans. Design), CEA
10.
Director Bureau of Indian Standards
5.
Umesh Chandra D. Chowdhury AGM DGM Power Grid Corpn. of India Ltd.
11.
Vice-President (Engineering)/General Manager Engineering, KECIL-RPG Transmission
6.
S.N. MandaI, Chief Design Engineer NTPC/K. Mohan Das, Addl. Chief Design Engineer, NTPC
12.
Vice-President (Technical) EMC
Convenor
P.K. Lal Director (E) Central Board of Irrigation and Power
AUTHORS Chaper 1
Introduction P.M. Ahluwalia VN. Rikh YD. Anand
Chapter 2
Tower Types and Shapes
Chapter 3
Tower Geometry M.L. Sachdeva H.S. Sehra
Chapter 4
Electrical Clearances M.L. Sachdeva
Chapter 5
Design Parameters
Chapter 6
Loadings Umesh Chandra D. Choudhury
Chapter 7
Design of Towers
Chapter 8
Testing of Towers S.D. Dand L. Khubchandani
ASSOCIATED TRAN,SRAIL STRUCTURESlTD.
(An Associate Co, of Gammon Group)
GAMMON HOUSE, 2nd FLOOR, VEER SAVARKAR MARG, PRABHADEVI, MUMBAI·400 025. TEL:5661400~1
::xtn: 4086/4043
Chapter 9 : Tower Materials, Fabrication, Galvanisation, Inspection and Storage B.N. Pai Chapter 10: Design of Foundation S.M. Takalkar D. Choudhury Chapter 11: Construction of Transmission Lines M.V Subbarayudu Each Chapter was finalised after Intense input by Shri P.M. Ahluwalia, Chairman of the Panel Covering Detailed Review, Modifications and Supplements followed by final Discussion and Acceptance by the Panel of Experts.
v
OTHER CONTRIBUTORS Vipin Parikh VP. Nathwani
L.c. Jain, Ex-Member, CEA H.S. Sehra, Ex-Director, CEA
1. 2. 3.
10. SAE, New Delhi
Powergrid Corpn. of India .-".
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S.L. Narasimhan D.P. Kewalramani Raisuddin Kamail Singh A.K Jain P;S. Aggarwal Alok Gupta Neeraj Kumar 5.
NHPC, Ltd.
S.B.C. Misra G.c. Tather VP.M. Nair S.N. Dubey 6.
NTPC Ltd.
L.V Rao A.P. Shatru S. Dasgupta 7.
ABB, New Delhi
Mata Prasad 8.
SERC Ltd., Chennai
K. Murlidharan SJ. Mohan
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KEC International Ltd.
L. Khubchandani S.D. Dand G.D. Rathod B.N. Pai M.V. Subbarayudu M.N. Dedhia P.L. Sehgal
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V Narayanan Dr. D.M. Lakhapati M.K. Mukherjee P. Bhattacharya N.T. Makijani RJ. Kulkarni Arun Arora
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Dr. P. Bose D.K Roy
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D.C. Bagde 13. BHEL, Bangalore
S. Chandra 14. UPSEB, Lucknow
VB. Singh Virendra Prakash A.N. Sinha Surendra Narain VK Srivastava A.K. Tiwari
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VJ. Ambawani KS. Dave 16. MPEB, Jabalpur
S.Z. Hussain Ashok Bajpai 17. MSEB, Mumbai
AJ. Khan 18. BIS, New Delhi
S.K Gupta S.S. Sethi Rachna Sehgal W.R. Paul 19. GERI, Vadodara
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The Central Board of Irrigation and Power brought out a manual on "Design of Transmission Line Towers" in 1977. The publication proved immensely popular and had to be reprinted twice because of its usefulness to utility engineers and manufacturers of transmission line towers. There have been many important developments since publication of the manual in 1977. The central sector generating companies like National Thennal Power Corporation and National Hydro Power Corporation made considerable impact on the generation scenario as also on EHV systems required for evacuation of power from the generating stations and also on inter-connection between various states for integrated system operation within the region. The regional grids are all in operation now and Power Grid Corporation of India is engaged in the task of establishment of National Power Grid. There have been considerable technological developments in the field of transmission engineering and the HVDC transmission and 800 kV transmission are going to play an important role in the National Power Grid. It was, therefore, felt necessary not only to revise the manual published earlier but also to make it a comprehensive one to include not only towers but also other aspects of transmission lines incorporating latest technological developments. Keeping this in view the Central Board of Irrigation and Power constituted a panel consisting of eminent transmission lines experts from all over the country in 1988-89 under the chairmanship of Shri P.M. Ahluwalia, Ex-Member, CEA, New Delhi to take up this important work. .
This Panel of Transmission Experts further set up in March 1992 a Steering Committee and also a Working Group to consider and make suitable recommendations on the implications of the proposed draft amendment to the Indian National Standard IS:802-1977 "Code for use of Structural Steel in Overhead Transmission Line Towers" issued in 1991 based on the 1987 draft on the report oflEC 826 of Intemational Electro-technical Commission. The outcome of efforts made by Steering Committee led to adoption of the probabilistic method of design as contained in "Guide for New Code of Transmission Line" published by CBIP in 1993. These recommendations were adopted in Part-I of IS-802 published in 1995. The present document "Manual on Transmission Lines" is outcome of the ceaseless efforts made and voluminous work done by the Panel of Experts on Transmission Lines. The various chapters contained in the publication were authored by groups of eminent practising experts and were thoroughly discussed in the meeting of panel at the time of finalisation. This publication will be immensely useful to Managers, Design and practising engineers of power utilities and Transmission Line Companies, Researchers, Testing Stations, Faculty Members and Students of Engineering Institutes in India and overseas. The Central Board of Irrigation and power wishes to acknowledge its grateful thanks to the authors of the different chapters for their expert contribution. Special thanks are due to Shri P.M. Ahluwalia, Chairman of the panel for the tremendous input and direction given for finalising the manual. Shri V.D. Anand, Chief Engineer (Retd.), CEA took it upon himself to go through the final manuscript meticoulously and correcting the same. The Board is also thankful to the members of the Committee for their valuable contribution. It is hoped that this publication will be well received by the engineering fraternity.
(C.V.J. VARMA)
Member Secretary Central Board of Irrigation and Power
Vll
Power projects are highly capital intensive. Transmission Line is the vehicle for optimum utilisation of power produced at power projects. Transmission Line suffers from limitless insurmountable handicaps - Funds, Environment, Ecology, Proximity of Objects. Forests, Right of Way, Changing Hostile Terrains, Uncertainties of Wind, Temperature, Snow and Lightning, and above all requirements of Reliability, Security and Safety. Overcoming all these adversities Transmission Line has to deliver to the consumer power at minimum cost and with maximum reliability. Tower is the most critical component of Transmission Line. CBI&P published in 1977 "Manual on Transmission Line Towers". That document became very popular in India and Overseas with Power Utilities and Tower Manufacturers. It had to be reprinted two times in 1988-89, CBI&P set up a Panel of Experts on Transmission Lines to review the Document considering the latest technological developments. In India, Towers were designed following Deterministic Method of Design as per Indian Standard, IS:8021977 Code of Practice for Use of Structural Steel in Overhead Transmission Line Towers. For almost a decade since 1980, CIGRE and IEC worked on the Probabilistic Method of Design for Overhead Lines, culminating in the publication of the Recommendatory Report IEC 826:1991, based on which CIGRE Working Group 22.06 sent a Questionnaire to various countries of the World, including India. The CBIP Panel of Experts on Transmission Lines examined the subject with speed and in depth through Steering Committee of top-most Transmission Experts. As a result India was one of the first countries in the world to adopt the Probabilistic Method of Design as contained in the sister Publication of CBI&P "Guide for New Code for Design of Transmission Lines in India" -1993. In accordance with the CBI&P Guide, Indian Standard IS:802" Code of Practice, for Use of Structural Steel in Overhead Line Towers" Part 1, Section 1 "Materials and Loads has been amended and published in 1995. Chapters 5 - Design Parameters -6 -Loadings; and 7 -"Design of Tower Members; of the Present Document deal with this subject. Other subjects dealt with in the Document are: Tower Types and Shapes - Chapter 2; Tower Geometry - Chapter 3; Electrical Clearances - Chapter 4; Testing" of Towers - Chapter 8; Tower Materials, Fabrication Galvanising Inspection and Storage - Chapter 9; Design of Foundations - Chapter 10; and Construction of Transmission Lines - Chapter 11. Each one of the Chapters was authored by eminent practising Experts incorporating latest technological advancements and practices and reviewed in depth by the members of the Panel of Experts on Transmission Lines before adoption. Special attention was given towards simplicity, clarity and completeness to make each chapter self-contained in all respects giving practical examples of calculation to facilitate practical application without hinderance. The Document has full acceptability as the Panel comprised managerial experts from Central Electricity Authority, Central Government Power Corporations, State Electricity Boards, Bureau of Indian Standards, Tower Testing Stations, Research Institutes and Transmission Line Manufacturing and Construction Companies. The mass of technological work could be accomplished by the untiring labours of the authors, members of the Panel of Experts and their organisations who worked behind the scene, CBI&P Management, Shri C.V.J. Varma, Member Secretary and Shri P.K. Lal, Advisor and other officers and staff of the CBIP. They worked ceaselessly for almost 9 years. lowe limitless gratitude and personal thanks to them for their co-operation and kindness in this great technical endeavour. IX
Power utilities, Transmission Line companies and their engineers located in the far-flung corners of India were always faced with the dearth of a single unified document on Design, Manufacture and Construction of Transmission Lines. This Manual will fill that void. It will be of great reference value to the Management and Practising engineers of Power Utilities and Transmission Line Companies, Researchers, Testing Stations, Faculty Members and students of engineering Institutes in India and Overseas.
P.M. AHLUWALIA Chairman CBIP Panel of Experts on Transmission Lines
Foreword Preface ~:
Introduction
1.1 1.2 1.3 1.4 1.5 1.6 1.7
'- 2.
Tower Types and Shapes
2.1 2.2
2.3 2.4
3.
Scope Types of Towers 2.2.2 Self-Supporting Towers 2.2.3 Conventional Guyed Towers 2.2.4 Chainette Guyed Towers Tower Shapes Tower DeSignation 2.4.2 Suspension Towers 2.4.3 Tension Towers 2.4.4 . Transposition Towers 2.4.5 Special Towers
Tower Geometry 3.1 3.2 3.3· 3.4 3.5 3.6 3.7 3.8 3.9
4.
Preamble Develppment of Power Systems in India Environmental and Ecological Awakening Privatisation Wave - Impact on Transmission Systems in India Philosophies in Design of Transmission lines New Concepts in Transmission Line Design Resume of Topics Covered In the Manual
Scope Tower Anatomy Bracing System Tower Extensions Tower Outline Tower Height Tower Width Cross-arm Spread Typical lengths of Insulator Strings on Transmission lines in India
Electrical Clearances 4.1 4.2 4.3 4.4 4.5 4.6 4.7
Introduction Minimum Ground Clearance Minimum Clearance above Rivers/lakes Environmental Criteria for 800 kV line . Air Clearances - General Consideration Clearances and Swing Angles on Transmission lines in India Conductor Metal Air Clearances XI
4.8 4.9 4.10 4.11 4.12 4.:13
Air Clearance - Analysis by CIGRE . Phase-to-Phase Air Clearances Clearance between Conductor & Groundwire Effect of Span Length on Clearances Clearances at Power Line CrOSSings Recommendation
ANNEXURES Annexure I - Spacing between Conductors Annexure II - 'Swing Angle for 800 kV Anpara - Unnao Line for Insulator Strings and Jumper APPENDIX - Investigation Studies on Clearances and Swing Angles for Indian Power System I
5~
Design Parameters
5.0 5.1 5.2 5.3 5.4
5.5 5.6
5.7 5.8
6.
Loadings
6.1 6.2 6.3 6.4 6.5
6.6 6.7 6.8 6.9 6.10 6.11 6.12 6.13 _6.14 6.15 6.16 6.17 7.
Abstract Transmission Voltage Number of Circuits Climatic CQnditions Environmental and Ecological Consideration . Conductor Earth Wire Insulator Strings Span
Introduction Requirements of Loads on Transmission Lines Nature of Loads Loading Criteria Transverse Loads (TR) - Reliability Condition (Normal Condition) Transverse Loads (TS) - Security Condition Transverse Load (TM) during Construction and Maintenance - Safety Condition Vertical Loads (VR) - Reliability .Condition Vertical Loads (VS) Security Condition . Vertical Loads during Construction and Maintenance (VM) - Safety Condition Longitudinal Loads (LR) -Reliability Condition Longitudinal Loads (LS) - Security Condition Longitudinal Loads during Construction and Maintenance (LM) • Safety Condition Loading Compinations under Reliability, Security and Safety Conditions Anti-cascading Checks . Brokel1wite Condition Broken Limb Condition for 'V' Insulator String
Design of Tower Members
7.1
General 7.1.1 Technical Parameters
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7.2.2 Graphical Diagram Method 7.2.3. Analytical Method 7.2.4 Computer-Aided Analysis 7.2.4.1 Plane - Truss Method or, 2-Dimensional Analysis 7.2.4.2 Space - Truss Method, or 3-Dimensional Analysis 7.2.5 Comparison of Various Methods of Stress Analysis 7.2.6 Combination of Forces to determine Maximum Stress in each member 7.3 Member Selection 7.4 Selection of Material 7.4.1 Use of hot rolled angle steel sections 7.4.2 Minimum Flange Width 7.4.3 Minimum Thickness of Members 7.4.4 Grades of Steel 7.5 Slenderness Ratio Limitations (KUR) 7.6 Computation of UR for Different Bracing Systems 7.7 Permissible Stresses in Tower Members 7.7.1 Curve-1 to Curve-6 7.7.2 Reduction due to bIt Ratio 7.8 Selection of Members 7.8.1 . Selection of Members in Compression 7.8.2 Selection of Members in Tension 7.8.3 Redundant Members 7.9 Bolts and Nuts Annexures Conductor Details I Earthwire 1\ III Design Loads Graphical Diagram Method IV Analytical Method V VI Computer Aided Analysis Input for 3D Analysis VII VIII Output Giving Summary of Critical Stresses Chemical Composition and Mechanical Properties of Mild Steel IX X Chemical Composition and Mechanical Properties of High Tensile Steel XI Section List Equal Section Commonly Used for Towers & As Per IS:808 (~art - V) 1989 UR Consideration for Bracing System ·in a Transmission Tower XII XIII Permissible Axial Stress in Compression XIV Reference Table for Maximum Permissible Length of Redundant Members XV Dimensions for Hexagon Bolts for Steel Structures
8.
Testing of Towers 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9
Introduction Testing Requirements Description of a Tower Testing Station Calibration Assembly of Prototype Tower Rigging Arrangements and Location of the Loadcells Test Procedure Testing of Prototype Tower· Special Requirements X1I1
8.10 Acceptance of Test Results 8.11 Material Testing 8.12 Presentation of Test Results 9.
Material, Fabrication, Galvani$ing, Inspection and Storage
9.1 Scope 9.2 " Material Quality Control 9..3 Specific Requirements of Fabrication 9.4 Operations in Fabrication 9.S Tolerances 9.6 Shop ,Erection/Proto-type Tower Assembly 9.7 Galvanising 9.8 Inspection 9.9 Packing and Storage Annexures I
II III
IV V
VI VII
Chemical Composition and Mechanical Properties of Mild Steel Chemical Composition and Mechanical Properties of High Tensile Steel " (a) Properties of Equal Angle Sections as per IS : 808 (Part V) - 1989 (b) Properties of Unequal Angle Sections as per I~ : 808 (Part V) - 1989 (c) Properties of Channel Sections Unit Weight of Plates Dimenf;ions of Hexagon Bolts for Steel Structures Ultimate Strength of Bolts Properties of Anchor Bolts. Metric Screw Threads as per IS : 4218 (Part-3)-1976 with ISO
Appendices
Appendix I ; Quality Assurance Plan I. Introduction II. Quality Objective" III. Quality Policy IV. Organisation of Quality Control Department V. "Quality Planning VI. Design and Drawings VII. Company Standards " VIII. Control on Inspection-EquipmentsIToolsiGauges IX. Material Management X. Incoming Material Inspection XI. Pre-production XII. In-Process Inspection XIII. Inspection and Testing of Finished (Galvanised) Material XIV. " Storage, Packaging and Handling Enclosures - A Sampling Plan for Incoming Material a. Sections, Accessories and Bought out Items b. Sampling Plan for Physical Properties" of Bolts, Nuts and Spring Washers c. Sampling Plan for Galvanising"Test for Threaded" Fasteners " d, Formats for Inspection Report for Steel StackinglPreliminary-(QCD-I) e. Format for Report on Bend Test f. Format for Report on Testing of Physical Properties ••
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Format for Inspection Report for Accessories - (QCD-4) .' Format for Inspection Report for Steel Test Tower - (QCD-5)
B. Sampling (a) (b) (c) (d) (e) (f) (g) (h) (i) G} (k) (I)
Plan for In-process Material Procedure Format for Quantity Control Report Format for Loading Report of Crates Format for Inspection and Loading Report of Fabrication Shop Format for Inspection and Loading Report of. Model Assembly Format for Inspection and Loading Report of Model Shop Format for Out-right Rejection Slip Format for Rectifiable Rejection Slip Format for Weekly Records of ShiftWise Acid Strengths Format for Galvanising Process Inspection Report Format for Galvanising Inspection Report Format for Testing Concentration of Prefluxing and Degreasing Solutions
Appendix II: List of Machines required for a well-equipped Tower - Fabricating Workshop Appendix III : Workshop Chart Appendix IV : Process Flow Chart for Fabrication of Tower 10.
Design of Foundations
10.1 General 10.2 Types of Loads on Foundations 10.3 Basic Design Requirements 10.4 Soil Parameters 10.5 Soil Investigation 10.6 Types of Soil and Rock 10.7 Types of Foundations 10.8 Revetment on Foundation 10.9 Soil Resistances for Designing Foundation 10.10 Design Procedure for Foundation 10.11 Concrete Technology for Tower Foundation Designs 10.12 Pull-out Tests on Tower Foundation 10.13 Skin Friction Tests ·10.14 Scale Down Models of Foundation 10.15 Tests'on Submerged Soils 10.16 Investigation of Foundation of Towers 10.17 Investigation of Foundation of a Tower Line in Service 10.18 Repairs of Foundations of a Tower Line in Service 10.19 Foundation Defects and their Repairs Annexures
Annexure . Annexure Annexure Annexure
-I - II - III - IV
xv
Typical Illustrations Tower Foundation Design Calculation Illustration Illustration Illustration Illustration Illustration Illustration Illustration Illustration Illustration Illustration 11.
-I • II - III • IV •V - VI • VII - VIII • 'IX -X
.
Construction of Transmission Lines 11.1 11.2 11.3 11.4
Survey Manpower, Tools and Plants and Transport Facilities Environmental Consideration Statutory Regulation for Crossing of Roads, Power Lines, Telecommunication Lines, Railway Tracks, etc. 11.5 Surveying Methods 11.6 Foundations 11.7 Erection of Super Structure and Fixing of Tower Accessories 11.8 Earthing 11.9 Stringing of Conductors 11.10 Hot-Line Stringing of E.H.V. lines 11.11 Protection of Tower Footings 11.12 Testing and Commissioning 11.13 References
Annexures
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Transmission Line Manual Chapter 1
Introduction
CONTENTS Page 1.1
PREAMBLE
1.2 DEVELOPMENT OF POWER SYSTEMS IN INDIA
2
1.3 ENVIRONMENTAL AND ECOLOGICAL AWAKENING
2
1.4 PRIVATISATION WAVE - IMPACT ON TRANSMISSION SYSTEMS IN INDIA
2
1.5 PHILOSOPHIES IN DESIGN OF TRANSMISSION LINES
3
1.6 NEW CONCEPTS IN TRANSMISSION LINE DESIGN
3
1.7 RESUME OF TOPICS COVERED IN THE MANUAL
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TRANSMISSION liNE MANUAL INTRODUCfION
1.1
PREAMBLE
1.1.1 Electrical energy, being the most convenient and cleanest form of energy, is finding the maximum usage the world over for development and growth of economy and therefore generation, transmission and utilisation of the same in ever increasing quantities as economically as the latest technological advancements permit, are receiving great attention. The technical, environmental and economic considerations involved in siting and development of power generation projects required for meeting the demand for electrical energy are gradually resulting in longer transmission distances and introduction of higher and higher transmission voltages, and use of high voltage direct current transmission systems. Thus transmission systems with voltages of 800 kV ae and t 600 kV de are already in operation in some of the countries and those with 1000/1100 kV ac and ± 750 kV dc have also been introduced :n some countries. In India, 66 kV, 132/110kV, 2301220 kV, and 400 kVae. and ± 500 kV dc systems are already in service and 800 kV ac systems are in the· process of implementation. All these systems owe there reliable performanee to a great extent to dependable transmission lines. Tower constitute a very vital component of transmission lines, as these performs the important functions of supporting the p·ower conductors and overhead ground wires at the requisite distances above ground level and maintaining appropriate inter -conductor spacings within permissible limits under all operating conditions. 1.1.2 With increase in transmission voltage levels, the heights as well as weights of towers have also increased and so has their cost. The transmission line towers constitute about 28 to 42 percent of the cost a transmission line. Therefore optimisation of designs of towers can bring about significant economy in the cost of transmission lines.. It is therefore imperative that transmission·line towers are designed so as to make use of materials and workmanship most effectively and efficiently. 1.1.3 The weight of a tower required for any specific applications is influenced to a great extent by the selection of tower configuration, choice of steel structurals for tower numbers, typ.e of tower, types of connections etc. On the basis of experience and designing skill, a tower designer can produce tower designs conforming to the governing specifications and bring about optimum reduction in tower weight without sacrificing stability and reliability features of the fiQished tower which are very important for structural reliability of a transmission line. These depend not only on the designs of tower and its foundation but also on the type of tower, development of structural arrangement of tower numbers, detailing of connections, quality of steel structural, accuracy in fabrication, proper soil investigations, use of foundations according to soil conditions at sites of tower installation, accuracy and adequate care in tower erection and proper maintenance of the erected towers. 1.1.4 Depending on the manner in which the towers are supported these fall in the following two broad categories :. 1. Self supporting Towers 2. Guyed Towers This Manual covers all aspects of designs of self supporting comprehensive manner.
~owers
and their foundations in a
~ ~ 1.~
DEVELOPMENT OF POWER SYSTEMS IN INDIA
1.2.1 In India, development of power over the years has been phenomenal. The installed generating. capacity has risen from a mere 2301 MW in 1950-51 to 85940 MW on 31st March, 1997. Matching with the installed generating capacity, transmission Systems have also grown. In 1950-51 there were only about 2700 Circuit KM of 132 kV lines and 7500 Circuit Km of 66/78 kV lines. These have grown to about liOO Circuit Km of 500 kV of HYDC lines, 32200 Circuit Km of 400 kV lines, 76400 Circuit Km of 220 kV lines, 97200 Circuit Km of 132 kV lines and 37700 Circuit Km of 66 kV lines (total 245,200 Circuit Kms). Strong interconnected transmission networks have been developed by each Electricity Board within the State boundaries. Regional Grids interconnecting State Transmission Grids have been built facilitating uninterrupted transfer of power within the region. National Grid at 800 kV and 400 kV is in the process of coming up spear-headed by Power Grid Corporation of India. Highlights of the power systems in India are given in Exhibits tl to 1.7. International comparisons with other countries are given in Exhibits 1.8 and 1.9.
1.3 ENVIRONMENTAL AND ECOWGICAL AWAKENING 1.3.1 Environmental and ecological considerations were not given so much importance in the past in the designs of transmission lines and their routing. However, availability of more sophisticated facilities has made it possible to investigate into the effects of electric and magnetic fields associated with transmission lines and understand and better appreciate the possible adverse effects of the above fields. In order to ensure that these fields least affect the way of life and ecology, the conductor configuration, tower shapes and transmission line corridors are so chosen that the magnitudes of radio interference (RI), television interference (TVI), audio noise (AN) and electrostatic fields radiated by the transmission lines are within safe limits and ecology is affected the least.
1.4 PRIVATISATION WAVE· IMpACf ON TRANSMISSION SYSTEMS IN INDIA 1.4.1 Exhibit No.l.lO gives an idea of the sector wise utilisation of funds as well as the total funds allocated for Power from 1951 to 1992 and the outlay for the 8th Five year Plan period. It shows that against the norm of at least 50% of the total allocated funds being utilised for Transmission and Distribution, the average availability of funds for Transmission and Distribution over the years 1951 to 1997 has been 32% only. This has resulted in lopsided development of T&D systems leading to most of the chronic problems faced by the consumers. 1.4.2 Development of power systems being highly capital intensive but essential for overall growth of economy, induction of Private Sector in the development of generation as well as T&D systems is engaging the attention of the Govt. of India. Some headway has been made as regards generation projects. However, the same has yet to take place for the T&D sector. With privatisation coming through for this sector also, the transmission system will get impatus for faster development. . 1.4.3 Need·based funds for development of transmission and distribution system during the 9th Plan period are of the order of about Rs. 110 thousand crores. These are over and above the fUl}ds required for generation projects which are about Rs. 160,000 crores for the 9th Plan period. It may not be physically possible for the country to make available funds of this order in the Pu blic Sector. Privatisation of generation projects is already underway. Many IPPs h~ve sponsored power generation projects which are actually not coming up physically. The main bottle-neck is transmission and distribution. l!nless a Private Sector Company has the facility to make returns from the power project, their interest in actual execution will be limited. For privatisation in Power Sector to take momentum, it is imperative for privatisation to take place in transmission and distribution, not limiting to power generation only.
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1.5 PHIWSOPHIES IN DESIGN OF TRANSMISSION UNES Before IEC:826 - "Report on Loading and strength of overhead lines' came out in 1985, 1987 and 1991, the design of transmission lines in India as also in several other countries was made as p.er design philosophy based on deterministic concept of Loadings and strengths with specified factors of safety {or the different operating conditions. Consequent to consideration of the approach outlined in IEC " 826. design philosophy based on probablistic concept with provisions relevant to Indian experience has been finalised for Transmission Une design and the existing 15:802 (Part 1/5ection 1) - 1995 code of practice for use of structural steel in overhead line Towers has been recast accordingly.
1.6 NEW CONCEPTS IN TRANSMISSION UNE DESIGN The new concepts in transmission line design philosophy include the followi 19 major changes in the design method:(i)
t~~
has ;. I f
to
\h::f
P .nes Y
\ ,
.nds tAt
Design based on limit load concept;
(ii) Use of probablistic method of Design; (iii)
Use of Reliability levels in transmission lines
design;
(iv) Use of Co-ordination in strength of line components; (v) Use of six basic wind speeds converted to 10-minutes average speeds orresponding to 10-meter height over mean retarding surface as the basis for wind loads on transmission lines instead of three wind zones corresponding to 3D-meter height over mean retarding surface in use earlier; (vi) Consideration of the effects of terrain category and topography of transmission line corridors in the design wind speeds; and (vii) Carrying out anticascading checks on all angle towers
1. 7
RESUME OF TOPICS COVERED IN, THE MANUAL
ilnd
1[0
1.7.1 The topics covered in chapters 2 to 11 of this Manual are briefly described below.
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1.7.2 Chapter 2 - Towers types and shapes
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ired t ..Ie .t;" n
ects :: \ 1.
1.7.2.1 This chapter describes fully the types of towers, tower shapes and designation of towers and brings out the essential differences between the various types of towers and the factors for preference of a particular type of tower to other types for some specific considerations.
1. 7.3Chapter 3 . Tower Geometry 1.7.3.1 'This chapter describes the various portions of towers and details the factors which determine tower height, tower width at various levels and the spread of cross-arms. It also describes the various types of bracing systems, insulator stings, and gives details of their composition, typical details of 66 kV,' 132 kV, 220 kV and 400 kV insulator strings, values of angles of swing and corresponding electrical clearances for insulator strings and jumpers for transmission lines already in service in India. analytical calculations of electrical clearances on transmission lines etc.
hpir n, It )' 'r
1.7.4Cliapter 4 . Electrical Clearances 1. 7.4.1 This chapter covers the requirements regarding the minimum electrical clearances to be maintained at tower and at mid-span between live parts of transmi~on line and from live parts to tower members for the various types of over voltages to which transmission lines of different voltage levels are subjected in service. It also deals with the minimum ground clearances, effect of span length on clearances and
3
the requirements regarding electrical clearances of power lines crossing over tele-communication circuits. railway tracks rivers, lakes etc.
.d' J,
1. 7 .5Chapter 5 - Design Parameters
1.7.5.1 This chapter covers the electrical, climatic and geological environmental and ecological considerations which influence the designs of transmission lines. It deals with the effects of shielcUng of lee-ward conductors by the wind-ward conductors of bundle conductors, span terminologies and theirsignificance in tower design, conductor creap allowance etc.
.;...
tit el ,I
1.7.6Chapter 6 - loadings
01
1. 7.6.1 This chapter defines the various types of loads. gives methods for their estimation for snow-free regions. deals with the Reliability Requirements - climatic loading under normal condition security requirements - Failure containment under broken wire condition, safety requirements loadings under construction and Maintenance and Anticascading Requirements 1.7.7 Chapter 7 - Design of tower-members
1.7.7.1 This chapter describes the methods of analysis of stresses in plane trusses and space frames, and deals with selection of grades and si~es of steel structurals for tower members, use, of high tensile steel and mild steel sections, slenderness ratio limits for members with calculated and uncalculated stresses. built-up members, permissible stresses in tower members and bolts, design of tower members and member connections. 1. 7 .8 Chapter 8 - Testing of Towers
1. 7.B.1 This chapter deals with the purpose of testing of towers, describes a typical tower testing station, celebration of load cells, rigging arfangements, locations of load cells in the test set- up, testing procedure, sequence of test loading cases. acceptance of test results and testing of tower material. 1.7.9Chapter 9 - Tower Materials, Fabrication, Galvanization, Inspection & Storage . .
.
,
1.7.9.1 This chapter deals with Material quality control, specific requirements of Fabrication covering preparation of structural assembly Drawings, shop Drawings and bill of materials, cutting means, operations in Fabrication such as straightening, cutting )i.e cropping, shearing, cutting, or saucing), binding, punching, drilling and marking tolerances, shop erection (horizontal or vertical), Method of Galvanising, Inspecti9n as per quality assurances plan, packaging of finished members and their storage. The chapter highlights the significance of planing as it has great bearing on optimum utjlisation of material and limiting the wastage. The chapter contains data on permissible Edge Security and Bolt Gauges, chemical and mechanical properties of Mild and High tensile steels, Properties of Equal! Unequal Angles, channels, Plates, Bolts/Nuts, and Anchor Bolts, it also contains a s'ample QAP, list of Tower Fabricating, Machinery; details of Galvanising Plant. and the tests conducted on fabricated members.
1. 7.10 Chapter 10· Design of Fuundations
1.7.10.1 This chapters deals with design requirements for various types of foundations for 3df - supporting towers. It brings out the importance of soil investigations and testing. classificaLivn ui soiis and excavations types of foundations and their application areas, procedure for their dC$igr,s l~tC. The chapter contains the permissible values of soil bearing capacities. permissible stress vaillt ': (,II concrete, reinforcement bar details and procedure for testing of foundatioils. A!)plkation of Ih~<::jl" :VIt·thods is
11
dempnstrated by typical detailed calculations of designs for aifferent types of Foundations.! he cnapter describes methods for investigating foundations and carrying out their repairs during construction 'stage and on lines in service.
11
1.7.11 Chapter 11 • Construction of Transmission Unes
b
1.7.11.1 This chapter covers all the stages from reconnaissance survey up to commissioning of lines. It deals with statutory regulations, line corridor selection from environmental angle, methods of tower erection, paying out of conductors under uncontrolled and controlled tension, final sagging, clamping in. spacer Ivibration damper/spacer damper instaJIation, jumpering, live line stringing of EHV line,s, protection of tower footings etc. It also covers the tests to be conducted before line energisation.
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5
EXHIBIT 1.1 Plan Outlays for Power Sector (Rs. Crores)
For Plan
Generation-
T&D
Total
First Plan (1951·56)
Z83
110
393
(195&-61)
310
116
426
Fourth Plan (1968-74)
699
321
1020
1725
722
2447
13851
5413
19264
25087
9185,
34272
57291
22280
79571
1,10,000
2.so.ooo
Sa:ond Plan
Fifth
Pl~
(1975--80)
Sixth Plan (l98Q..85)
Seventh Plan (l98~90)
Eighth Plan (1992-97)
NinthPlan
1,40,000
'(1997-2002)
I
I
t
r O+------y----~r-----~~--~-
EXHIBIT 1.2 Installed Generating Capacity
(MW) Yl'ar
Nuch>ar
Hydro
Thermal
Tolal
1~F)!) SI
0
S5~
1742
2Wl
1<11)0 IiI
I,',
1917
2736
4653
1~!71l71
421;
6J83
7810
J.t1i13
1~J7X, t~1
li·lll
10883
15207
2!)i31i
19848::,
ItllJ:l
14460
27030
4:L~S
1989-90
1565
18307
43764
63636
19
IS/iS
18753
45768
66086
19~192
1,X')
19194
48086
6906S
199:L,9:{
20(1:')
19576
50749
723jli
1!I!l]-94
20DS
20379
54370
76754
19~'4-~5
2005
20829
58110
80944
1995-%
222S
20976
60086
8J287
19Y6,97
")')') r:.
21fi45
61149
85019
Iw"-' .... ')
<:OOX> IroX)
'7(XXX}
60000
~
mx>
~ ~
J(XXX)
ro'XJ
I~~I
1%0-61' 1~71
19'7S-19 I~ ~90 1mg1 1991-92 ~93 1993-94 1~ 1m-96 1996-97
y-
EXHIBIT 1.3 Electricity Generation (LW~L
\1l:)
Year
Nuclear
Hydro
Thermal
Total
1950. 51
0
2860
~!i98
5~58
1960-61
0
7837
!iIOO
lti937
1970-71
1339
29961
Sf:i54X
1978-79 i584 . 85
2770
25248 52594
4715~J
1/j2S23
4075·
53948
9883€i
1568[)9
1989-90
4625
62116
245438
2:i1),
1990-91 1991 . 92
6140
. 71640
264330
l~ll
5530
72760
287030
7•. { ~
301360
}
324050
1992·93 1993-94 1994·95
6730
69870
5400
70460
178697 186550 208740 224760 24819()
5646
82511
267891""
3S6i'l54
1995-96
7923
72383
299470
:179776
1996-97
9024
68618
317158
394800
~
i.a \'. ·11 }-i':/ (oJ)
l
"-'0000 .Q)OO)
3~
:i
~
:: ,~..
""
JOOOOO
_Nudear ~
1III(~dro
ElThemul
DlOOO
lnm 1000.» ~
0
Year
21
EXHIHIT 1.4 It'ngth of Transmission Unes (CK\1) Transmis!lion
19511·51 lYtifl-61 1970-71 1980-tH 1.985-86 1991l-91 1992-93 1995·9h lY9ti·97
VI) \t(ijll'
HVl.C (Ol)
1f,67
1tjJI)
tV
1321111) kV
TOlal
\1)139
Z340
7952
11111
3BM
47XI)~
4tili)l)
59nx
83140
120214
162!:140
1&57
;jh]4
X: 4 h.'
&'1186
20H521
218447
2045226
lXOOO.-----------------------------------------------__~__~ ItXXXlO
B HVDC &400 \IV
,
o ZJOIZlO k. \' I II IJUIIOII" iii "78166144 kV
l~H
1960-61
t.m71
1~81
1985-86
1990-91
9
199'2-93
1995-96
1996-97
EXHIBIT 1.5 All India power Requirement Past Trend Energy Requirement
Peak Load
(MkWh)
(MW)
1988-89
206331
:B551
1989-90
228662
36327
1990-91
246722
38986
1991-92
259000
41674
1992-93
282739
43636
1993-94
324417
54707
1994-95
349346
58904
1995-96
376679
63490
199&-97
413490
63853
Year
~r---------------------------------------------~
I~
10lXXl0
o 19'~'9
1I~90
199G-91
1991·92
1992·91
Var
1~94
1994-93
199'.96
1996-97
EXHIBIT 1.6 AJI"lndia Power Requirement Forecast for 9th, 10th, 11th Plan Year
Energy Requirement (MkWh)
Peak Load
1997-98
436258
734~8
1998-99
469057
7R936
1999-00
502254
84466
2000-01
535903
90093
2001-02
569650
95757
2006-07
781863
130944
2011-12
1058440
176647
(MW)
Source: 15th Electric Power Survey uf India
D FMrO'R• .,dre_nt
• Puillold
Yell'
11
EXHIBIT 1.7 Revised Fund Requirement Generation 1&D (Rs. Billion) Year
Capacity Addition (MW)
Generation
T&D
Total
97·98
6000
210
126
336
9H-99
6500
227
137
364
99·1)1)
7000
245
147
392
1)1)·01
7750
271
163
434
""r
01·1)2
8500
297
179
476
~a
02-03
9250
324
194
518
Ch
03·\)4 .
10000
350
210
560
£g
04·1)5
11000
385
231
616
05-06
12125
424
255
679
Total
78125
2733
1642
4375
..
~
'-
.,
'>'
Source: The India Infrastructure Report Published by Ministry of Finance Govt of India HUI
lnd Iud,
IOOT-----------------------------------------~l~
r
q
J'
1~
J~r'\a
!
L\\\\\"IT&D I'll4l.I Gcucrab:o
-+- Ca c' Additioo
Kon Mex ~,,(\
. K.h
P' '1li PrJ'Jl
Sri 1.; I
Swedl
U.K. Year
U~ U~_4l
-
Yu.. s
SOL .f'
EXHIBIT 1.8 International Comparison (If Installed Capacity and Generation
r· , Billion) Generation (GWH)
Installed Capacity (M\\) Counlr~' /Yrar
1960
1970
1980
1990
1960
1970
1980
19~1!
Argetina
3474
6091
11988
17128 2520 52892 104140· 98600 11738 13220 103410 99750 8508 6603 75995 11480 17554 9000 56548 194763 9500 29274 27195 9137 6869 30703 1289 34189 73059 775396 333100 16470
10459
2172i
396i6 2&53 139485 377518 300620 16910 38710 246415 368770 22652 23876 112820 6981 17150 8000 185741 577521 35000 66954 84099 15277 18032 121871 1668 96695 284937 2354384 1293,878 59435
4700i
Bangladesh
990
Brazil
4800
Canada
23035
China Egypt
1167
Finland
2834
France Germany
)
Greece Hungary India Indonesia Iran Iraq Italy
~ .",'11
:. Additicr!
Japan Korea (DPR)
,
Mexico Norway Pakistan Phi11ipines Poland Sri Lanka Sweden U.K. USA USSR Yugoslavia
21851 28393 615 1465 5580 319 2 350 17686 23657 J048 6607 656 765 6316 94 36702 186534 66721 2402
11233 42825 240180 4357 4312 36219 47540 , 2488 2477 16271 907 2197 680 30408 68262 3400 7318 12910 2334 5176 13710' 281 15307 62060 360327 166150 6972
33293 81999 67000 3583 10422 62711 82585 5324 4842 31247 2786 5300 1200 46824 143698 5500 16985 20238 2518 4632 24723 422 27416 73643 630111 266757 14030
Sourl"t': Powt'r Ot'vrlopment in India 1995-96
13
22865 114378 59400 2639 8628 72118 118986 2277 7617 20123 1400 852 56240 115498 9139 10813 31121 26 2731 29307 302 34740 136970 844188 292274 8928
45460 204723 115900 7591 21185 146966 242605 9820 14541 61212 2300 6758 2750 117423 359539 16500 28707 57606 8727 8666
64532 816 60645 249016 1639771 740926 26024
7732 211324 440317 618000 37100
45i36
393713 389000 34126 27463 264300 29810 53200 28410 190327 757595 53500 114277 108836 37999 ~5249
128201 3150 139515 298496 2807058 1652800 83033
EXHmrr 1.9 International Comparison of Electricity Prices (Indian Paise) Cost per Kwh Domestic
Country
Industrial
Portugal
397
591
Germany
339
647
Italy
316
528
Spain
268
582
OBCD
258
378
United Kingdom
227
406
Denmark
221
666
Luxembourg
221
384
Ireland
215
432
Netherlands
202
415
Belgium
197
5tH
Greece
197
341
France.
184
490
India
211
93
SI T.
Source: Report on Energy Prices & Taxes· lst Quarter 1995
700 600 SIX) It
-1400 11.0 I
1 300 200
100 0
1 i 110
>.
i
M
..
~
;
It
e ~
E
i
~
"II
·2
t
j
~
.B
Ig
oJ
:I
CAuIdry
'a
~
]
EXHIBIT 1.10 Sector·wise Utilisation of Funds for Power ~tl
(Figurt's Rs. crorf's) SI. Period No.
.
Total Funds utilised for Power
Sector wise Utilis.ation Generation
Transmission & Distribution
Others
Amount
%
Amount
%
Amount
%'
23
~
95
21
1. 1st F.Y. Plan (1951·56)
260
105
40
132
2. 2nd F.Y. Plan (1956-61)
460
250
54
115
51 . 25
3. 3rd F.Y. Plan (1961-66)
1252
777
62
301
24
174
14
4.
Annual F.Y. Plan (1966-69)
1223
676
55
291
24
256
21
5.
4th F.Y. Plan (1969-74)
2931
1505
51
768
26
658
23
6. 5th F.Y. Plan (1974·79)
7541
4467
59
2016
27
1058
14
7.
Annual Plan (1979-80)
2473
1429
58
720
29
324
13
8.
6th F.Y. Plan (1980-85)
18913
12116
64
4706
25
2091
11
9.
7th F.Y. Plan (1985-90)
38169
24528
64
9847
26
3794
HI
10. Annual Plan (1990-91)
10470
7003
67
2375
23
1092
10
11. Annual Plan (1991·92)
13904
10373
75
2661
19
870
6
12. 8th F.Y. Plan (192·97) Outlay
79730
49196
62
22432
28
8102
10
"
15
Transmission Line Manual Chapter 2
Tower Types and Shapes
CONTENTS Page 2.1
Scope
2.2
Types of Towers
2.2.2
Self-S~pporting
Towers
2.2.3 Conventional Guyed Tower
1
2.2.4 Chainette Guyed Tower
7
2.3
Tower Shapes
7
2.4
Tower Designation
7
2.4.2 Suspension Towers
8
2.4.3 Tension Towers
8
2.4.4 .Transposition Towers
8
2.4.5 Special Tower
CHAPTER 2
Page 1
TOWER TYPES AND SHAPES
1
1 1
7 7
7 8 8
8 8
2.1
SCOPE
2.1.1 The tower of various shapes had heen used in the past without considering detrimental influence on the environment. With conservation environmentalists attracting the highest attention and the public becoming more and more conscious of the detrimental effects of transmission line towers on the environment and occupation of land, transmission line tower designers have been endeavouring to develop towers with sllch shapes which blend with the environment. Other factors responsible for changes in shapes of towers are the need for the use of higher transmission voltages, limitation of right-of-way availability, audible noise level, radio and T.V. interference, electrostatic field aspects, etc. The types and shapes of Transmission Line Towers used in India and in other countries are discussed in this chapter. 2.2
TYPES OF TOWERS
2.2.1 The types of towers based on their constructional features, which are in use on the power transmission line are ~ven helow :
steel conforming to IS: 8500 is not readily available in the country, steel conforming to BS 4360 Gd 50B/ASTM A 572IJ1SNDE or any other InternationallNationai standards can be used. Some of the countries such as ; apan, USSR, Austria, Canada, France, etc., have explored use of other material such as steel formed angle sections, tubular sections, aluminium sections, etc., for fabrication of towers. In the case of heavy angle and long span crossing towers, some of the countries namely Russia, Norway, France, etc. are using single phase self-supporting towers. Selfsupporting towers usually have square/rectangular base and four separate footings. HoweveN'wer voltage narrow-based towers having combined monoblock footings may be used depending upon overall economy. Self-supporting towers as compared to guyed towers have higher steel consumption. Self supporting to\Ve~~~sed}~r compactline design. Compact tower may comprise fabricated steel body, cage and groundwire peak, fitted with insulated cross-arms. Qmwa~tion ~s also achi~ye~..E1..~angement of phases, ~ll~ing V insul_ator strings, etc. Compact towers iUiVereduced dimensions and require sm3iier right-of-way and are suitable for use in congested areas and for upgrading the voltage of the existing Transmission Lines ~Iso. Self-supporting towers are shown in Figures 1 & 2.
I.
Self-Supporting Towers
2.
Conventional Guyed Towers
2.2.3
~.
Chainette Guyed Towers
2.2.3.1 These towers comprise portal structures fabricated in "Y' and "V' shapes and have been use~ in some of the countries for EHV transmission lines upto 735 kV. The guys may be internal or external. The guyed tower including guy anchors occupy much larger land as compared to self-supporting towers and as such this type of construction· finds application in long unoccupied, waste land, bush tracts in Canada, Sweden, Brazil, USSR etc.
These are discussed in the subsequent paragraphs. 112.2
Self·Supporting Towers
Self-supporting broad based/narrow based latticed steel towers are used in India and other countries. This type \oftower has been in use in India from the beginning of this century for EHV transmission lines. Self-supporting towers e covered under Indian Standard (IS : 802) and other' ational and International Standards. These are fabricated, sing tested quality mild steel structurals or a combination f tested quality mild steel and High tensile steel structurals onforming to IS:2062 and IS:8500 respectively. As H.T.
Conventional Guyed Tower
2.2.3.2 Compact guyed towers are used on compact lines. The phases are arranged in such. a way that the phases are not interspersed by grounded metal parts of Tower. The phases can be placed in different configurations and are insulated from the supports. The conventional guyed towers
1
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ZONTAUWAS" OWER
••
~
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•
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.a ..
-' .
J)()UBLE CIRCUIT TOWER
SINGLE CIRCUIT TOWER
B-DELT AlCA T HEAD TOWER
...
C-VERTlCAUBARREL TOWER
'.
PHASE-I
I'HASE-2
E-TRIPLE POLE STRUCTURE FIGURE I : SELFISUPPORTING
TOWERS
PHASE-J
~ ~
""...,
~
~
"""" $::l
5.
INSUI,ATED
'FABRICATED TOWER BODY
COMPACT TOWER
MULTICIRCUIT TOWERS
FIGURE 2
4
...
and compact guyed towers are shown in Figure 3.
(ii)
Horizontal/Wasp Waist Type
2.2.4
(iii)
Delta/Cat Head
(iv)
H-Structure Type
Chainette Guyed Tower
Chainette guyed tower is also known as cross rope suspension tower, and consists of two masts each of which is supported by two guys and a cross rope which is connected to the tops of two masts and supports the insulator 'strings and conductor bundles in horizontal formation .. For angle towers, the practice is to use three separate narrow based masts each for carrying one set of hundle conductors or ~lse self-supporting towers. Each . narrow based mast is supported with the help of two main guys. Typical chainette guyed towers for suspension and angle location are shown in Figure 4.
In India, tower shapes at (i) and (ii) are used for single circuit line whereas tower shape at (i) has been used for double circuit and multi-circuit lines. In other countries al the above shapes have been used. Tower shape at (i) is structurally more stable and ideally suitable for multi-circuit lines. whereas tower shape at (ii) offer better performance from the consideration of audible noise, radio and television interference i.. electrostatic potential gradient at ground level and at the edge of the right-of-way. These towers shapes are shown in Figures 1 & 2.
2.2.5
Guyed towers will be~overed in a separate I~anual
2.4
TOWER DESIGNATION
2.3
TOWER SHAPES
2.4.1
Broadly, towers are designated as under:
Tower shapes in use are as follows:
(i)
Suspension Tower
Verticallbarrel Type
(ii)
Tension Tower
,
(i)
DOUBLE TENSION i
SUSPENSION :INSULATOR STRING
FIGURE 6 : ARRANGEMENT OF INSPAN TRANSPOSITION
....
Tower Types and SI
(iii)
Transposition Tower
(iv)
Special Tower
2.4.2
SUspension Towers
These towers are used on the lines for straight run or for small angle of deviation upto 2° or 5°. Conductor on sUspelisioh towers may be sUpported by means of I-Strings, V·Strings, or a combination of I & V Strings. 2.4.3
Tension Towers
Tension towers also known as angle towers are used at locations where the angle of deviation exceeds that
permissible on suspension towers and/or where the towers are subject to upliti loads. These towers are further classified as 2°/SO-15°, 15°.30°, 30°·600IDead end towers and are used according to the angle of deviation of line. One of the classes of angle towers .depending on the site conditions is illso designated as Section Tower. The section tower is introduced in the line after 15 suspension towers to avoid Cil
2.4.4
Transposition Towers
TranspoSition lOWers are used to transpose the. conductors in three sections in such a way that each! by rotation occupies each of the three phase positiO£ circuit. A typical transposition tower is shown in Figl In another transposition arrangement called 'i~ transposition' (Figure 6) the transposition is carri near a tension tower due to greater ground ele aVailable near the tower than in the mid span. multiple tension insulator strings are connected baq back through a strain ·plate. III the central phase ~ plate, a Single suspension insulator string having alf double the No. of inSUlator discs and air gap distan~ Suspended. The baJance work oomplises PJacem~ Jumpers. ,
: 1
2.4.5
Special Tower
These towers are used allocations Such as ~' involving long span river and valley crossings, cf crossings, pOwer line crossings etc. falling Oll the line r~,
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Transmission Line Manual Chapter 3
Tower Geometry
CONTENTS Page 3.1
3.1
Scope
3.2
Tower Anatomy
3.3
Bracing System
3
3.4
Tower Extensions
5
3.5
Tower Outline
6
3.2
3.6
Tower Height
6
3.2 .
3.7
Tower Width
23
3.8
Cross-arm Spread
26
3.9
Typical Lengths of Insulator String on Transmission Lines in India
28
1 3.1.
3.2'0-.1
3.2.,) 3.2.3.1
3.2.'1 3.2.4.1
v"at""" v
TOWER GEOMETRY 1
The Chapter describes anatomy of tower and factors involved in determining the outlines of the towers. The selection of an optimum outline together with right type of bracing system contribute to a large extent in developing an economical design of transmission line tower. The geometry of a tower has also a bearing on aesthetic values. The tower anatomy and tower outline are discussed below:
3
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S
SCOPE
3.2
TOWER ANATOMY
3.2.1
A tower is constituted of the following components as shown in Figure-1
3
Peak Cross Arm Boom Cage Tower Body Body Extension Leg Extension Stub/Anchor Bolts and Base Plate Assembly
5 ~
A brief description of each component of the tower is given as under:
3.2.2
Peak
3.2.2.1 It is the portion of tower above the top cross arm in case of vertical configuration tower and above the boom in case of horizontal configuration tower. The function of the peak is to support the groundwire in suspension clamp and tension clamp at suspension and angle tower locations respectively. The height of the peak depends upon specified angle of shield and mid span clearance.
3.2.3
Cage
3.2.3.1 The portion between peak and tower body in vertical configuration towers is called Cage. The cross-section of cage is generally square and it may be uniform or tapered throughout its height depending upon loads. It comprises tower legs interconnected by bracings are used in the panel of cage where cross-arms are connected to the cage or where slope changes for proper distribution of torsion.
3.2.4
Cross-Arm
3.2.4.1 The function of a cross-arm in case of vertical configuration tower is to support conductor/ground wire. The number of cross arms depend upon number of circuits, tower configuration and conductor/groundwire arrangement. The cross-arm for ground wires consists of fabricated steel work and that for conductor may be insulated type or consist of fabricated steel work. The dimension of a cross-arm depends upon the line voltage, type and configuration of insulator string, minimum framing angle from the requirement of mechanical stress distribution etc. At large angle of line deviation, rectangular/trapezc1idal cross-arm with pilot string on outer side are used to maintain live conductor to grounded metal clearance. The lower members of the cross -arm are called main members and the upper members as tie members/compression members depending upon direction of vertical loads.
2
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't3.2.E
Cross arm--
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Bracing
3.3.1
Tower body Body extension
Concrete level
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Ground level
Single Circuit Tower
Double Circuit Tower
3.3.2 3.3.2.
Vertical/Barrel Type Towers
Boom level
3.3.3 3.3 n 1
Bracing Concrete level
'Horizontal/Wasp Waist ..Type Tower
Figure 1: Tower Anatomy 3.3."
3.2.5
Boom
3.2.5.1 It is generally a rectangular beam of uniform cross-section in the middle, but tapered in the end sections and form part of horizontal configuration towers (self supporting, guyed etc.) The boom is attached to the tower body and it supports power conductors.
3.2.6
Tower Body
3.2.6.1 Tower body is the main portion of the tower to connecting cagelboom to the tower foundation or body extension or leg extension. It comprises tower legs inter-connected by bracings and redundant members. It is generally square in shape. In another arrangement, a tower body comprises two columns connected on one of their ends to the foundations and on the other ends to the boom to which conductors are attached through the insulator strings.
ge Waist lev
3.3
BRACING SYSTEM
3.3.1
Peak, cage, tower body, body extension, leg extension, etc. comprises legs, bracings and redundants. The bracing and redundants are provided for inter-connecting the legs as also to afford desired slenderness ratio for economical tower design. The Framing Angle between bracings, main leg members and (both bracing and leg member) shall not be less than 15° Bracing patterns are single web system, double web or warren system, Pratt System, Portal System, Diamond Bracing system, and multiple bracing system. Each of the bracking system, shown in Figure 2, is described below.
3.3.2
Single Web System
I.e level
-
3.3.2.1 It comprises a system either of diagonals and struts or of diagonals only. In diagonal and strut system, struts are designed in compression while diagonals in tension, whereas in a system with all diagonals the members are designed both for tension and compressive loads to permit reversal of the applied external shear. This system is particularly used for narrow base towers~ in cross-arm griders and for portal type towers. This system can be used with advantage for 66 kV single circuit line towers. It is preferable to keep the four faces identical in case of 66 kv single circuit tower using single web system as it results in lighter leg member sizes. Single web system has little application for wide base HV and EHV towers.
3.3.3
Double Web or Warren System
3.3.3.1 This system is made up with diagonal cross-bracings. Shear is equally distributed between the two diagonals, one in compression and other in tension. Both diagonals are designed for tension and compressive loads in order to permit reversal of externally applied shears. The diagonal bracings are connected at their cross points. The tension diagonal gives an effective support to the compression diagonal at the point of their connections, and reduces the unsupported length of bracings which results in lighter sizes of bracings members. This system is used for both large and small towers and can be economically adopted through out the cage and body of suspension and small angle towers and also in wide base large towers. In lower one or two panels in case of wide base towers, diamond or portal system of bracing is generally more suitable from the consideration of rigidity. These bracings result in better distribution of loads in legs and footings.
3.3.4
Pratt System
3.3.4.1 Shear is carried entirely by one of the diagonal members under tension. Other diagonal is assumed to be carrying no stress Struts, i.e.,horizontal member in compression are necessary at every panel
Tower Geometry
4
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Warren System
Pratt System
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Portal System
View 2-2 Hip Bracing Diamond Bracing System
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Multiple Bracing System (Lighter Tower)
(h) Multiple Bracing System (Heavier Tower)
provlae commul1Y 10 me oraclng syslem. Aovamage or mls SYSlem IS mal me sizes or olagonal members would be small because these are designed for high slenderness ratio in order to make them in tension. This type of bracings result in large deflection of tower under heavy loadings, because the tension members are slender in cross-section than compression members for similar loading. If such a tower is over-loaded, the in-active diagonal will fail incompression due to large deflection in the panel, although the active tension member can very well take the tension loads. This system of bracing impart torsional stresses in leg members of the square based tower and also result in unequal shears at the top of four stubs for the design.
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3.3.5
Portal System (Shear Divided 50:50 between Diagonals K·System)
3.3.5.1 The diagonals and horizontal members are designed for both tension and compression forces. The horizontal members are supported at mid-length by the diagonals, one half of the horizontal members is in compression and the other half in tension. The portal system is used for approximately the same size of panels as that for Pratt System of bracings in conjunction with warren system of bracings. It has been found advantageous to use the portal system for bottom panels, extensions and heavy river crossings towers when rigidity is a prime consideration. If hill side or comer extensions are anticipated, the portal panel is particularly attractive due to its versatility of application. 3.3.6
Diamond Bracing System
3.3.6.1 Somewhat similar to the Warren system, this bracing arrangement can also be derived from the Portal system by inverting every second panel. As for each of these systems, all diagonals are designed for tension and compression. Applicable to panel of approximately the same size as the pratt and portal systems, this arrangement has the advantage that the horizontal members carry no primary loads and are designed as redundant supports. 3.3.7
Multiple Bracing System
3.3.7.1 The EHV towers where the torsional loads are of high magnitude, the cage width is kept large to resist the torsional loads. Standard Warren system, if used, give longer unsupported lengths of legs and bracings which increases the weight of tower disproportionately, for such tower, multiple system of bracings is used. The advantage of this system in addition to reduction in forces in the bracings is that the unsupported lengths of leg members and bracings are reduced substantially thereby increasing their strength and reducing the member sizes. Although there is an incre.as.e in the number of bolts, fabrication and erection cost, yet the above system gives overall reduction in weight and cost of steel. The bracings on the transverse and longitudinal faces may be staggered as reduction in tower weight is achieved by staggering the bracings. The system is preferable only for suspension and medium angle towers. In heavy angle and dead end towers, in order to have more rigidity, bracing on transfers and longitudinal faces should not be staggered. 3.4
TOWER EXTENSIONS
3.4.1
Body Extension
Body extension is used to increase the height of tower with a view to obtaining the required minimum ground clearance over road crossings, river crossings, ground obstacles etc. Body extensions upto 7.5 m height in steps of 2.5 m can be used and thus form a part of standard tower. For body extensions having greater heights say 25 m, the suitability of the standard tower is checked by reducing the span length and angle of deviation. Practice in the tower industry is also to specify negative body extension i.e. a portion of the tower body is truncated. For lines transversing in hilly terrain, negative body extension can be used in tension towers from consideration of economy.
6
Tower Geometry
3.4.2
Leg Extensions
3.4.2.1 Leg extensions are used either with anyone leg or any pair of legs at locations ~here footings of the towers are at different levels. Leg extensions are generally used in hilly regions to reduce benching or cutting. The alignment of leg extension is done with the first section of a tower. Installation of leg extension calls for high degree of expertise in tower erection. 3.4.3
Stubs/Anchor Bolts and Base Plate Assembly
3.4.3.1 Stubs/anchor, bolts and base plate assembly connect the tower body/body extension including leg extension to the foundations. Cleats are provided with the stub to offer resistance against uprooting 0f the stub. A stub set consists of four members whereas the number of anchor bolts depends upon uplift and shear on the bolts.
3.5
TOWER OUTLINE
3.5.1
Tower Outline is fixed from the requirement of minimum ground clearance, terrain type, right of way limitation, electrical clearances etc. Tower outline is defined in terms of the following parameters:
3.5.1.1 Tower Heights Minimum ground clearance Maximum sag including creep effect of conductor Length of suspension insulator string assembly Vertical spacing between power conductors Location of ground wire Angle of shield Minimum mid span clearance Tension insulator Drop 3.5.1.2· Tower Width At Base or Ground level At Waist level At Cross-arm/Boom level 3.5.1.3 Cross Arm Spread Type of insulator string assembly Suspension, I-string or V-string. Tension Pilot Swing angle Suspension String Assembly Conductor jumper Phase to phase horizontal spacing Each of the above parameters is discussed in the subsequent paragraphs 3.6
TOWER HEIGHT
3.6.1
Minimum Ground Clearance
'\ .;.1
laid down by Power Telecommunication vo-oralnallon vUlIlIlllll~~, ncyulaLlvlI~ 'U' • " ...... _ ... _ Crossing on Railway Tracks-1987 laid down by Indian Railways and other applicable regulations laid down by different National Agencies like Indian Road Congress, Ministry of Surface Transports etc. The values of clearances required for lines of different voltage ratings are given in Chapter 4 of this manual.
; of the l'l"hing , f leg 3.6.2
I: .J leg rooting Il:! upon
Maximum Sag including Effect of Conductor Creep
3.6.2.1 The size and type of conductor (AAC, ACSR, AAAC. ACAR, AACSR), climatic conditions(wind,temp,snow)and span length determined the conductor sag. The maximum sag of a conductor occurs at maximum temperature and still wind condition. The maximum sag is considered in fixing the height of a line support. In snowy region, the maximum sag may occur at 0° and nil wind for ice coated conductors. 3.6.2.2 Creep in a conductor is defined as permanent set in the conductor. It is a continuous process and takes place throughout its life. The rate of creep is higher initially but decreases with time since in serVice. Creep compensation is provided by either of the following methods :-
way neters:
(i) (ii) (iii) (iv)
Pretensioning of conductor before stringing Over tensioning of the conductor in the form of temperature correction By providing extra ground clearance By a combination of partly over tensioning of conductor and partly providing extra Ground clearance.
The procedure for determining sag and creep compensation in respect of conductor is dealt with in Chapter 5 of this manual. 3.6.3
Maximum Sag of Groundwire/Minimum Mid Span ClearanceS/Angie of Shield The function of groundwire is to provide protection to the power conductors against direct lightning stroke and to conduct the lightning current to the nearest earthed point when contacted by a lightning stroke. The above functions are performed by the ground wire (s) based on selection of angle of shield, mid span cfearance and coordination of groundwire sag with that of conductor. The material and size of groundwire (galvanized stranded steel, alumeweld, ACSR, ACAR, AAC, AACSR) depends upon the criteria for sag coordination and extent of mutual coupling. The effect of cre.ep in galvanised stranded steel groundwire being negligible is not taken in account while deciding the s.ag. The location of groundwire (s) determine the height of groundwire peak. Single groundwire has been used in India for transmission line towers upto 220 kV having verticallbarrel type configuration and two groundwires for horizontal/wasp waist type towers of all voltages and 400 kV verticallbarrel type towers. The detailed procedure for coordination of groundwire sag. with that of power conductor and values of mid span clearances and angle of shield are dealt with in Chapters 4 and 5.
3.6.4
IUlations
Length of Insulator String Assembly·
3.6.4.1 The length of suspension insulator string in combination with minimum ground clearance and maximum conductor sag determine the height of (i) lowest crossarm in case of verticallbarrel/Delta type suspension tower and (ii)boom in case of horizontal wasp waist type suspension tower whereas the length of suspension insulated string in conjunction with phase to grounded metal clearance determines the spacing between cross- arms in case of verticallbarrel type tower. The length of an insulator string is a function of insulation -level (BIL and SIL), power frequency voltage (service voltage dynamic over voltage) and service conditions (Pollution, attitude humidity). The depth of the jumper is affected by phase to grounded metal clearance which its.elf is determined from BIL, SIL,
Tower Geometry
8
service voltage, short circuit level, altitude, humidity etc. For determining electrical clearances, the length of the suspension insulator string is defined as the distance between the centre line of conductor and the point of contact of ball hook/anchor shackle with the hanger/U-bolt whereas the length of tension insulator string is defined as the distance between the point of attachment of the string to the strain plate at cross arm upto the jumper take off point of tension clamp. The length of V string for the purpose of determining the height of tower is the vertical distance between the lower main member of cross arm and ,centre of lowest conductor. For preparing clearance diagram the nearest live part from the grounded metal has to be considered. The number and size of discs., length of single and double suspension and tension string for various system voltages are given in Chapter 4 of this manual. Typical arrangements of Insulator Strings are shown in Figures as indicated below: Figure 3 Figure 4 Figure 5
Typical Insulator String Arrangement for 220 kV AC Transmission Line Single Suspension Insulator String for 400 kV AC Transmission Lines Typical Arrangement of Single Suspension String for 400 kV Lines with Twin Bundled Conductor Typical Arrangement of Double Suspension String (For 400 kV Lines with Twin Bundled Conductor) Single Tension Insulator String for 400 kV Transmission Lines Typical Arrangement of Double Tension String for 400 kV Lines with Twin Bundled Conductor 400 kV AC "V" Suspension with AGS Clamp for Twin Moose 400 kV AC Quadruple V Suspension Set for ACSR Bersimis (35.1 6) Quadruple Deadend Assembly for 400 kV AC ACSR Bersimis 800 kV Single V-Suspension Insulator String for Quad "Moose" Bundle 300 KN x 2(31 pcs. per String) 800 kV Single V-Suspension Insulator String for Quad "Moose" Bundle 400 KN x 2(29 pcs. per String) 800 kV Double V-Suspension Insulator String for Quad "Moose" Bundle 300 KN x _ 2(31 pcs. per String) ± 500 kV DC "vn Suspension Insulator Strings for Four ACSR Bersimis (35.1 mm Dia) ± 500 kV DC Quadruple Tension Insulator String Four ACSR Bersimis
Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16
3.6.5
Vertical Spacing between Power Conductors/Minimum Vertical Phase to Phase Clearances/ Minimum Phase to Grounded Metal Clearances
3.6.5.1 The vertical spacing between power conductors and between power conductor and groundwire is controlled by mechanical considerations (galloping/clashing and electrical consideration) (phase to phase and phase to grounded metal clearance requirements. The minimum phase to phase and phase to grounded metal clearances are generally determined on the basis of lightning impulse levels for lines of voltages upto 300 kV. For lines voltages as are 300 kV, the minimum phase to phase and phase to grounded metal clearance are based on switching impulse level. The minimum phase to grounded metal clearance is affected by power frequency. The dynamic over voltage/service, voltage, altitude, humidity and temperature also. The minimum phase to grounded metal clearance is ascertained from the lightning impulse level for lines upto 300 kV and switching impulse level for lines voltages above 300 kV as also power frequency dynamic over voltagel service voltage considering altitude, humidity and temperature also. The minimum phase to phase and phase grounded metal clearances for different I.
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1. Anchor shackle 2. link strap 3. H. H. ball eye 4. T. S. arcing horn 5. Socket clevis 6. Spacing yoke
7. Bottom guard ring 8. U clevis 9. Susp ension clamp 10. Armour rod
Qi ....~ G)
Figure :10. 400 kV A ( Quadruple V Suspension Set for ACSR Bersimis (35.1 ct»
('I)
~Cb
~
"~·jl
r 1_
Nom. 5900 Min. 5745 72S
'1. Anchor shackle 2. Yoke
plate
3. Anctllr shackle 4. Yoke plate 5. Arcing horn 6. Ball clevis This bolt will be provided with sped .. 1 nut for corona g protection co
130 1130.
175 1100 11001210
670-820
3910
1 - 6 1 3 1 max.
....
U"\ ~
14. Extension link 15. Dead end assembly
725
..-/
---- -
-.-- -
=:-.
....
~
;:
""'
~
• .:.IL ____ .:.-_
I.. figure 11
1300
7. Socket clevis 8. Yoke plate 9. Anchor shackle 10. Yoke plate 11. (levis eye 12. Corona central ring 13. Sag adjusting device
':'-:::-=-=-.-
.. /
Quadruple Oeadend Assembly for 400kV AC ACSR Bersimis
11650· ~
0)
r I
Item
Description Towtr fitting
Q). ·U-Clevi& Q) Horn holder
G>
=.
'(3)
=
oj
U"I
= CD IJ"I
..,g
2.30
=
U"I
C7'
240 c:>
V'I
oj
2
Steel Steel ~t~'!t tension
2 2
Porcelain
29x2
2
(j) (])
Arcing horn Socket Clevis
Steel Ductile iron
2
G>
Yoke
Steel
1
@
Clevis eye Steel Suspension chimp Aluminium alloy
4
90° Clevis Clevis Ductil.. iron Ht~~1 tension sf
1 1
Steel ':Ilgh tension steel Anchor shilckle ~i~~1 tension
2
@ @
90· (levis eye Yoke
~xtension
link
Cat No.
2
Steel
l@ Tower Fitting
~~s~:~on I~ul
Steel
@. Arcing horn
@
:Q)-
Ball Clevis
Main material Reqd.
4
4
1 4
Min. breaking strength of string Suitilble conductor size of clilmp Type of ball and socket pilrts Note:- 11 General Tolerance on a) Length of hardware components :!: 37mm .b) Insulator string:!: 190mm 21 Air gaps between live parts and tower body shall be as per clearance diagram
450
~
1800 max.
~
Ci) (!)
~
Figure 12: BOOkV
Insulator String for o.uad 'Moose' Bundle
~
rigure 'JL: oOOr
inyle '{ -S\Jspt;.nSlun IoISU.dt0. 300KN
X
S.
"in~
fL.
(JaL 'M .)S,
B "d .
2 (31 pcs./String) 11560
-'
l
~
co
6''5i's
Item
//~'" ""',.
CD
~'5i'c9.
<=> <=>
.~
-.3 Ln
·'~~O "+/ /,9 i?o
,
'<90",
<=>
co
",0+
Ln '-D
./
a>
U-Clevi& Horn holder
(j) @ Q)
@ @
l® @ @
Detail of(!)- Tower Fitting
250
<=>
290
Ln
a-.
<=>
Tower fitting
Q) @ (j) @ (j)
(])
,~
Description
Ball C(evis
Main material Reqd. Steel 2 Steel Steel Mign. tension !;t~1!1
~u~enslon 'SL I .. tor
Porcelain
2 2 2
Z9xZ
Arcing horn
Steel
Arcing, horn Socket Clevis
Steel Ductile iron
2
Yoke
Steel
1
Clevis eye Steel Suspension clamp Aluminium alloy 90 0 Clevis Clevis Ductile iron High tension 90 0 Clevis eye steel Steel Yoke High, tension Extension link steel Anchor shackle L~~~~l tension
Cat No.
2 4
4
4 1 1 1
2
4
Min. breaking strength of string Suitabl. conductor size or clamp Type of ball and socket parts
Ln
-.3
Note:-
450
General Tolerance on al Length of hardware components .t·39mm bl Insulator string ~187mm 21 Air gaps between live parts and tower b"ody shall be as per clearance diagram 1)
1800 Max.
Figure 13: 800 kV Single V - Suspension Insulator String for o.uad 'Moose' Bundle 400KN x 2 (29pcs.lString)
I\)
o
6045 5000
I
<:> VI oj
Arcing horn Item
D D
Hain material Reqd. High 4 90° Clevis eye "Steel tension 4 Compression damp Aluminium Description
3) Horn holder
1(4)
Ball clevis
Steel High., tension sf~e
5) Suspension clamp Porclean Steel 6) Arcing horn Steel 7) Arcing ring
i)
L®
Ir9) 1~
Corona shidd ring Aluminium Socket eye
Ductile iron
90° Clevis Clevis Ductile iron Q.uadruple yoke Ductile 'ron
(orona shield ring
2 c:>
2
VI oj
31x2
\_ .. _--_ ..
2
,
1
Details
0
f
CD -Clevis
,,:
1
. : ~':
Eye
.,,';" ,.
;
25
2 4
2 Steel 11) Yoke 4 Ductile iron 90° Clevis Clevis 12) S~a adjustable 4 Steel pia e 4 Anchor shackle I ~t~~1 tension ~4) Steel 2 (15) Adjustable pl.te I Suitable conductor size of clamp Hin. breaking strength of string excePtcompression clamp . Type of ballal"idsocket parts
®
Cat No.
Note: 1. Genenll tolerance on
,
I
I .j.
II
t----cJ---h·-
I·al Length of hardware components :!:53 mm lill Insulator string :!:190 mm 2. Air gaps between live parts and tower body shalt be as per clearance diagram
'"
Qi ~ ~
2S
Figure 14: 800 kV Double Tension Insulator String for Quad 'Moose' Bundle 300KNx2 (31 pes./String)
G) (t)
~
~
~""~'"""
.~"::.~"::. ",# -i:--Y
",.;"::.'0"::.
r-
l.I"I -J"!
~.. 320 700
Figure
_/
1. Anchor shackle 2. Ball eye 3. Socket clevis 4. Spacing yoke S. Bottom guard ring 6. Susp ens ion clamp 7. U-tlevis 8. Armour rod
457 1100
15: :!:500 kV DC IV' Suspension Insulator Strings for Four A CSR BERSIMIS. (35'.1 mm dial
Nominal
in central Dosition I\) I\)
725
= =
r-
'" oJ"
CIO
130
17S
'100 /100/150 Min.
95
170x38=64U 490'Mu. 8810 with sa
1. Anchor shackle 2. Yoke plate 3. Anchor shackle 4. Yoke plate 5. Ball clevis 6. Socket clevis 7. Spacing yoke 8. Anchor shackle 9. (orona ring 10. (levis eye 11. Spacing yoke 12. Adjus table plate 13. Extension link 14. Dead.end damp 15. Dead Elnd damp
72S
osition
I.
11.00
-/
r--.(
,
rlr~.~nd .-.~ c:>
~ ...,
~
7'-
1.- -
"
"" 1420
"
~
.....
'" oJ"
~
Qi ...,~ G) (I)
o
3(I)
Figure
,"",.
16: :!:500 kV DC Uuadruple'Tension Insulator String Four ACSR BERSIMIS
~
lVYV~1 I~ ylv~" "I rlyur~:s I qC1J C1IIU I qUJ.
vvnerever elevauon omerence oelWeen twO aOJacem
tower is considerable, the vertical clearances betWeen phases at the tension tower is determined by phase to phase switching/lightning impulse clearance between the highest point of the shielding ring/atoning horn of the tension insulator string of the lower phase and the lowest point of the jumper of the upper phase.
3.6.6
Tension Insulator Drop
3.6.6.1 The tension string/assumes position along the line of catenary of the conductor and therefore its inclination with respect to horizontal varies with change in sag. The Tension Insulator Drop is the vertical displacement of the jumper leg point w.r.t attachment point of tension string at strain plate. The drop is maximum under maximum sag condition and is lowest at minimum sag condition. While drawing the clearance diagram it is necessary to check the clearance of jumper for both minimum and maximum drop conditions of insulator string. 3.6.6.2 In case of considerable difference in the elevations of adjacent towers, the jumper leg and of insulator string of the tower at lower elevation may go up due to null point lying outside the span and the insulator drop maybe negative leading to insufficient live conductor to grounded metal clearance between the jumper and the cross-arm. Under such cases, the jumper may be modified to obtain the appropriate clearance.
3.7
TOWER WIDTH
3.7.1
The width of the tower is specified at base, waist and cross-arm/boom level.
3.7.2
Base Width
3.7.2.1 The spacing between the tower footings i.e. base width at concrete level is the distance from the centre of gravity of the corner leg angle to that of the adjacentcorner leg angle. The width depends upon the magnitude of the physical loads imposed upon the towers (calculated from the size, type of conductors and wind loads) and also depends upon the height of the application of external loads from ground level. Towers with larger base width result in low footing cost and lighter main leg members at the expense of longer bracing members. There is a particular base width which gives the best compromise and for which total cost of the tower and foundations is minimum. Through experience covering over a number of years, certain empirical relations have also been developed which are good guide in determining the base width. The base width of the tower is determined from the formula as given below: B B M K
= = = =
k~M Base width of tower at ground level in centimeters Overturning moment, in kg-m A constant
The value of K varies from 1.35 to 2.5 and 1.93 is an average value. The determination of the correct value of the constant for suspension and angle towers becaus.e of such a wide range suggested, may lead to differing results. With a view to arriving at a simpler relationship, Figures relating to total weight of tower and their base widths are tabulated in Table 3.2 for typical towers of all voltage classes both single and double circuits. It is seen that the base width generally varies between 1/4 to 1/6 of the overall height of the tower upto concrete level- the values may be 1/6 for suspension tower, 1/5 for medium angle towers and 1/4 for heavy angle towers. Where the way leave is a problem, the design is optimized with the maximum permissible bas.e width.
24
Tower Geometry
b
I
,h
~------~----~--~~-
0:
l
I~a~ ror a..-jset
Figure17(a):Vertical Spacing Between Two Adjacent Cross-arms or Two Power Conductors in Case of Suspension Tower
9, should be limited to oc for determini.nO.,minimum vertical spacing
tForO, <'cr< B2
/Fora:
H+b+h H+b+h (x, +B+C) - S Cos 9, H=(x2+B+C)-S Cos 92 or (x2+B+C) - S Cos 9,
b = (S+x,+B+C) Cos r:C
h = (a +off set) tan oc a =b tan oc ' a = (S2+x,+B+C)+Sin
oc
b=S CO~r' +(x, +B+C) Cos
1j" -
whichever is
(S+x2+B+C) Cos oc h=(a+off set) tan oc a= S Sin 9, +(x, +B+C) Sin oc or =(S+x2+B+C) sin oc Value of 'a' should correspond to greater value of 'b'
Notes: 9, 92 B C x, x2 S
\
, [
b
h
a = = = = = = =
Swing angle of the suspension string. Maximum swing angle of the suspension string. Flange width of the nearest projecting angle section Distance of centre of gravity of the main angle section Electrical clearances corresponding to BIUSIL Electrical clearances corresponding to dynamic over voltage/power frequency voltage. Lenoth of suspension insulator string. The minimum value of string length shall be used
/)
y
L. T.~~_ _-+----I
Figure 17Ibl: Vertical SpiKing Bet"'een two Adjacent Cross...:.arms . or two Power Conductors in Case of Tension Towers
oc > 9. Vertical spacing = Y+b+h
Y+b+h
Depth of jumper terminal point below cross-arm level D=
1.10 x Maximum electrical clearance corresponding to Bil or Sil
h=
D Cos 93 + (x, +BtC) Cos oc or (D+X2+B+C) Cos oc (a+St Sin 41/2+off set) tan oc
b=D Cos 93+(x, +B+C) Cos oc or Whichever is greater D Cos 9. + (x2+B+C) Cos oc h = (a+St Sin ,/2+offset) tan oc
D Sin 93 +(x, +B+C) Sin oc or (D+X2+B+C) Sinoc
a = D Sin 93 + (x, +B+C) Sin oc or a = D sin 9. +(x2+B+C) Sin oc
a= a=
Sag of minimum span excluding twice length of tens.ion insulator string . Y' = Sag of the minimum span specified This value may -be worked out for maximum sag as well as minimum sag and a relevant value is adopted.
26
Tower Geometry In medium and heavy angle towers, for the bracings to carry minimum possible loads, it is suggested that the base width and the slopes of the leg members may be adjusted in such a manner that the legs when extended may preferably meet at the line of action of the resultant loads. This reduces the forces in bracings to a large extent and a stronger and more stable tower emerges. Typical slopes of bottom most leg member with vertical for various voltage rating tower are given in Table 3.1 Table 3.1 Typi.cal Slopes of Tower Legs for Various Voltages
3.7.3
Voltage Rating
Type of Towers
Slope of Leg
Upto 220 kV
Suspension angle dead end
4°_9° 70-11 ° 8°-13°
400 kV and above
Suspension angle dead end
8° -12° 10° - 17° 11° - 15°
Width at Waist Level
I.,iQ
3.7.3.1 Width at the waist level is defined as the width at waist line in case of horizontal/wasp waist towers. For horizontal configuration, the width at:the waist level is found to vary from 1/1.5 to 1/2.5 of base width depending upon the slope of the 199. 3.7.4
Width of Cross-Arm Level
3.7.4.1 Width at cross-arm level is defined as the width of the tower at the level of lower cross- arm in case of barrel type tower. This width is mainly decided by torsion loading. The torsional stresses are evenly distributed on the four faces of the square configuration tower. The larger width reduces torsional forces transmitted to the bracings below that level and thus helps in reducing the forces in bracings of the tower body. The cage width is decided in a manner that the angle between lower main member and the tie member of the same cross-arm and that between bracings and belts is not less than 15° in line with the general structural engineering practices as an angle less than 15° may introduce bending stresses in the members. 3.8
CROSS-ARM SPREAD
3.8.1
The cross arm spread of a suspension and a tension tower is a function of Basic Impulse Level/ Switching Impulse Level and power frequency over voltage, configuration of insulator strings, angle of swings of suspension string in case of suspension tower and that of jumper in case of tension tower, phase to phase spacing etc. These parameters are described in Chapter 4 of the Manual.
3.8.2
Length of Cross-arm for Suspension Towers
3.8.2.1 Alternative-I: Insulator String-I Configuration The length of the cross-arm is determined corresponding to nil swing and two swing an ales and the
~I ~I E
:
".
'~f ~IL
III ,. "'II I IIIc ~o
!
II~
I :;. b
CD
"n)
n:
-::
CO
-,:::::
,
=:...- --=.J
"'l
':1
a
¢
~~-~
d
TABLE 3.2 Base width top hamper width and height for typical 66/132/220/400 kV standard towers --------
SI. No.
---
------
Type of Tower
----
Width at Concrete level
Top Hamper
(mm) 1 1
2.
3
4.
5.
6.
7.
8.
9.
66 kV: Double Circuit A (0-2°) B (2°_30°) C (30°_60°) 66 kV: Single Circuit A (0-2°) B (2°-30°) C (30°_60 0 ) 132 kV:Double Circuit A (0-2°) B (0-15°) C (15°_30°) D (30 0 -60'/D.E.) 132 kV: Single Circuil A (0_2°) B (0-15°) C (15°-30°) D (30°-60"/D.E.) 220 kV:Double Circuil A B C
· · · · · · 220 kV Single Circuit A· · · B · · C · ·
220 kV: Single Circuit Horizontal Configuration A B C
· ..· ·· ·
400 kV: Single Circuit A (0-2°~ B (2 0 -1 0) C ~15O-300) D 3O°-60°/D.E.)
(mm)
3
2
Width at top hamper/width at concrete level
------
Total height above ground level
Base width at concrete level: Total height above concrete level
8+0 (Tension)
C+O (Tension) 0+0 (Tension)
Horizontal distance between conductors
(mm)
(mm)
Tower weight
(mm) 5
4
(kgs)
7
6
8
9
10
3.075 4,400 4,500
1,000 1,075 1,150
1:3.08 1:4.10 1:3.91
19,600 18,895 20,090
1:6.1 1:4.3 1 :4.4
2,170 2,060 2,440
4,270 4,880 6,000
1.382 2,100 2,782
1.675 2,590 3,050
760 915 1,220
1:2.20 1:2.80 1 :2.50
15,910 15,425 16,240
1:9.5 1:6 1:5.3
1.030 1.030 1,220
4,040 4,270 4,880
1.064 1,283 1,783
4,050 5,490 4,880 6,400
1,250 1,540 1,665 1,840
1:3.24 1:3.56 1:2.87 1:3.47
26,230 26,545 26,545 28,060
1:6.4 1:4.83 1:5.44 1:4.38
3,965 3,965 3,965 4,270
7,020 7,320 7,320 8,540
3.10 3.97 4.60 6.00
3,920 4,224 4,828 6,135
1,300 1,400 1,600 2,000
1:3.0 1:3.0 1:3.0 1:3.0
23,140 22,060 22,685 24,060
1:6 1:5.2 1:4.7 1 :4
4,200 4,200 4,200 4,200
7,140 6,290 7,150 8,820
2.17 2.89 3.74 4.82
7,000 8,900 10,344
2,260 2,500 3,000
1:3.09 1:3.56 1:3.45
31,650 31,300 29,900
1:4.52 1:3.52 1:2.90
5,200 5,200 5,200
9,900 10,100 9,700
4.15 6.04 8.69
4,500 5,300 7,000
1,500 1,700 2,000
1:3.0 1 :3.12 1:3.50
28,555 29,080 31,680
1:6.3 1:5.48 1:4.52
5,200 5,250 6,700
8,500 10,500 12,600
2.57 3.60 5.04
4,000 4,800 5,800
2,640 3,300 3,600
1 :1.5 1:1.5 1 :1.61
18,050 18,600 20,200
1:4.51 1:3.9 ; :3-:5
-
7,400 8,800 8,800
5,000 6,700 _ 6,900 7,500
2,000 2,000 2,200 2,400
1:2.5 1:3.35 1:3.13 1:3,12
34,100 33,100 33,010 33,410
1:6,82 1:4.94 1:4.78 1:4.45
7,800 7,800 7,800 8,100
12,760 12,6l«l 14,000 16,200
2,200 2,600 2,600 3,000 3,000
0.220 0.260 0.260 0.2632 0.2632
35,900 35,400 35,750 35,925 35,875
0.2803 0.2843 0.2815 0.3193 0.3198
... .-
12,800 13,300 15,400 14,300 18,700
+ 500 kVDC
A+O (Susp.) B+O (Susp.)
Vertical spacing between conductors
10,000 10,000 10,000 11,400 11,400
.-
...
...
6.517 11.261 14,473 17.603
... ... ...
_.
-
..--.
Tower Geometry
28
load (maximum) and vertical load and transverl~ load (average) and vertical load. At nil and medium swing angle the electrical air clearance cJrresponds to lightning impulse level for lines having voltages upto 300 kV and to switching impulse level for lines having voltages upto 300 kV and to switching impulse level for lines having voltages above 300 kV voltage and at maximum swing angle the electrical air cle,!lr§ince corresponds to power frequency dynamic over voltage/rated voltage. c~ ,,-
~:
,\1
3.8.2.2 Alt~rnative-II: Suspension Insulator String-V Configuration I
The length of the cross-arm is determined corresponding to electrical clearances(BIUSIL) and the angle of the V-insulator string. The criteria for determining electrical clearances in case of lines upto 300 kV and those exceeding 300 kV is same as applicable in case of I-Insulator string. 3.8.2.3 The electrical clearance diagrams considering length and configuration of string and electrical air clearances (Ref. Chapter 4) are drawn to determine the length of cross arm and the same is checked against galloping/clashing depending upon the exposure of the lines to such conditions.
The electrical clearance diagrams for suspension tower with I and V - string is given in Figure 18. The analytical calculations for electrical clearances are given in Annexure-I where reference is to be made to Figure 20. 3.8.4
Length of Cross-arm for Tension Towers
3.8.4.1 On tension tower without the pilot string, the length of cross-arm is determined corresponding to Nil swing and swing angles specified for the jumper and the corresponding electrical air clearances (BIUSIL Power frequency voltage). The length of cross-arm is also determined with jumper swing limited to 15° with the use of pilot string and the corresponding electrical air clearance (BIUSIL). 3.8.4.2 The electrical clearance diagrams considering length of tension string, jumper swing angle, electrical air clearances,angle of deviation of the line are drawn and cross arm length is arrived at. For large angle towers (60°)/ and dead end towers, provision of unequal cross-arms, rectangular/ trapezoidal cross-arm and use of pilot Insulators Strings and links may be considered where necessary for determining the cross-arm length.
The electrical clearance diagram of a tension tower is given in Figure 19. The analytical calculation for electrical clearance is given in Annexure-I where reference is to be made to Figure 21.
3.9
TYPICAL LENGTHS OF INSULATOR STRING ON TRANSMISSION LINES IN INDIA
No
3.9.1
Typical details of insulator strings (suspension and tension) and swing and clearance of suspension insulator strings and jumpers for existing lines in India are given in Tables 3.3 and 3.4. Typical Swing Angles and Electrical Clearances for Tension String (Single/Double) Jumper adopted in India are given in Table 3.5.
(' b 9 b2
,v
I .
v-s ti;ng
I - String Airangement
Ari~rlgerr.ent
Figure 18: Electrical Clearance Diagram Suspension Tower
Notes: C B S 81 82 X1 X2
= = = = = = =
Distance of centre of gravity of the main angle sections Flange Width of the nearest projecting angle sections connected to main angle members. Length of suspension string Swing angle of the suspension string Maximum swing angle of the suspension string Electrical clearance corresponding to BIUSIL Electrical clearance corresponding to dynamic over voltage power frequency voltage Maximum swing angle of String = ~2 = 1/2 of the inc! uded angle of V String Length of X-arm
I-String S Sin 91+X 1+B+C or S Sin 92 + X2+B+C
V-String
•
Tower Geometry
30
D =Depth of Jumper = 1.10 x Maximum electrical clearance corresponding to BIL or SIL Length of cross arm
=
St Sin..t+ D Sin 93 +Xl+B+C 2 or =St Sin + 0 Sin 94 +X2+B+C
""2
$ =Angle of line deviation 83 =Jumper swing and corresponding clearance XI 84 = Maximum jumper swing and corresponding clearance X2
I9.L-J
Isef ~St.1 Sin~ ")
~
I •
tJ~
Un r~ ~ ,...I
'
('f
.>-
I
r
x2 =1860
VI
wtz
>
,.,t,
~t,
--
Xt,
T
1 4 - - - 1 - - - - - LM
------1
wb ~--~----LB---------~~
Figure 20: Electrical Clearance Diagram-Suspension Tower (Annexure-I: Analytical Calculations)
32
Towe; Geometry
-
Tal
--
,
\1
II \1
I I
>
~~
---xtl
.-,-
lB
Z
I101 mt
I 101m
K
L.
~l
I I I I \
I I r
t
wb
1 4 - - - - - + - - - L B - - - - -.. ...,1
r
Ia I\ 1
TABLE 3.3 Typical Details of the Insulator Strings Adopted in India on Transmission Lines at 66 kV to 800 kV AC and ± 500 kV HVDC
Line Voltage (kV)
Suspension String
Tension String
Type
No. of Discs
Length (mm)
Types
No. of discs
Length (mm)
5 2x5
965 1255
6 2x6
1070 1575
9 2x9
1630 1915
10 2x10
1820 2175
14 2x14
2340 2640
SIT DIT SIT DIT SIT
15
400
SIS DIS SIS DIS SIS DIS SIS
23
± 500 DC
VIS DIS
66 132 220
OIT
2x~5
2915 3345
3850
DIT
2x23
5450
2x38
7120
QuadlT
4x38
8450
2x40 2x35 4x35 1x40 2x40 2x29 2x31
7000 7550 7800 7000 7250 See Fig.14 & 15
QuadlT
4x35
9800
QuadlT
2x31
See Fig. 16
800 POWER GRID
V(A Towers) V(S&C Towers) SIS (Pilot D&E Towers) V (Pilot D&E Towers) V
UPSES
Note: (i) (ii) (iii)
Size of discs for insulator strings upto and including 220 kV Voltages is 255x145 mm. Size of discs for suspension and tension strings for 400 kv voltage is 280x145 mml255x145 mm and 280x170 mm respectively. Size of discs for 800 kV system of POWERGRID are 255x145 mm of 120 KN discs for DIS and SIS (Pilot D&E towers) and V (Pilot for D&E towers) and 280x170 mm 01210 KN for V (A, S & C towers) and quad tension string. In case of UPSES, the size of disc is 320x195 mm of 300 KN both for suspension and tension strings.
TABLE 3.4 Typical Swing Angles and Electrical Clearances for Suspension Insulator Strings adopted . in India on Transmission Lines at 66 kV to 800 AC and ± 500 kV HVDC SI. No.
Line Voltage (kV)
Assumed Value of Swing of Suspension String from Vertical (degrees)
Minimum Clearances Specified (mm)
1.
66
15 0 30 0 45 0 60 0
915 760 610 610
34
Tower Geometry (Table 3.4 Contd.) 2.
132
15° 30° 45° 60°
1530 1370 1220 1070
3.
220
15° 30° 45°
2130 1830 1675
22° 44°
3050 1860
4.
400 I-String
(
C \
)
c
5.
800 I-String
V-String Power Grid UPSEB
Power Grid 20° 25° 41° 55°/64° 105° to 115° V=90°
c
5600 4400
y
1300
5100/5600 5000/5500
TABLE 3.5 Typical Swing Angles and Electrical Clearances for Tension String (Single/Double) Jumper adopted in India on Transmission Lines at 66 kV to 800 kV and ±500 kV HVDC
SI. No.
line Voltage (kV)
Assumed Value of Swing of Jumper from Vertical (Degrees)
Minimum Clearances Specified (mm)
1.
66
10° 20° 30°
915 610 610
2.
132
10° 20° 30°
1530 1070 1070
3.
220
10° 20°
2130 1675
4.
400
20° 40°
3050 1860
5.
± 800
Power Grid 15°/20° 25°/30° 40°/45°
5600 4400 5000
" I
.
• '.1
w
..vV,
ANNEXURE·I
Analytical Calculation for Electrical Clearances on Transmission Lines (Refer Figures 20 and 21)
1.0 NOTATIONS
=
H
=
S
B
=
C
=
ocococ= T'
y~.
M'
B
Y2 =
W1
=
W!1,W I2 = W'1'W:? = ~.Y
=
Z
=
h"hm,hb
=
M = LT,LM,L B =
4>
D
=
=
Height of hanger Overall length of suspension insulator string upto the lower tip of corona control ring. Swing angles of suspension insulator string Specified electrical clearances to be maintained at swing angles corresponding to 91 & 92 respectively. Flange width of the nearest projecting angle sections connected to main and tie angle members. Distance of centre of gravity of main angle section Angle between main and inclined tie members of top, middle and bottom cross-arms. Vertical distance from underneath the cross-arm to nearest tip of corona control ring from centre line of tower corresponding to 91 & 92, Vertical distance from underneath the cross-arm to the farthest tip of corona control ring from centre line of tower corresponding to 91 &92, Horizontal distance from centre line of tower to nearest tip of corona control ring corresponding to 01 & 92, Horizontal distance from centre line of tower to the farthest tip of corona control ring corresponding to 91 &92, Half width of tower body at top cross arm level Half width of tower body at level corresponding to ~'1' ~12 Half width of tower body at level corresponding to XI1 , X!2' . Slopes of legs Height of Corona control ring Length of top, middle, bottom cross arm from centre line of tower body. Spacing between the conductors of bundle or jumpers. Height of top, middle and bottom cross arms Angle of deviation of line Jumper depth
36
Tower Geometry
2.0 ELECTRICAL CLEARANCE ON SUSPENSION STRINGS 2.1
Underneath the Cross-arm
At Angle of Swing
Electrical clearance Ayailable
6,
K,
=Y, -
(B + C)
=H +(8-M) Cos 6, - N. Sin 9, -
(B+C) X,
2
62
K2
= Y2 -
(B + C)
=H +(S'- M) Cos 9
2-
N Sin 92 - (B+C) X2 2
2.2
Electrical Clearance from Tower Body
Horizontal Clearance = (X\1 - WI') Cos B ~ X,
9, Horizontal Clearance
=
WI + Y, tan B
XI' =
~-
S. Sin 6, -
NCos'9, -
(B+C)
2
Y1
=
W12
=
WI + Y2 tan ~
X12
=
~
H + S. Cos 9, + NSin 9, - (B+C) 2 (XI2 - W12) Cos ~ ~ X2
-
S. Sin 62 -
NCos 92 -
(B+C)
2 H + S. Cos 92 + NSin 92 - (B+C) 2 Electrical Clearance from Lower Cross-ARM Tie (Inclined) Member Y2
2.3
-
W\1 =
tan oem (Lower X-arm) =
=
hm
Perpendicular distance to Tie member from the line point' is shortest. If oem < 9,. then clearance is required to be computed at swing angle of string corresponding to oem If oem > 9, and less than 92 , then the clearance is minimum when angle of swing is 91 Distance from lower tip of corona control ring to lower cross-arm tip
=P
p =(Lm - ~ ) + S. Sin 9, - N Cos 8,
Clearance available
=rJ=-lH+5 COs 9, + ~ Sin 9,) - Ptan u,,1 Cos 0., • (B+C) ~ X" i =[V - Y, . p tan aml Cos Urn· (B+C) ;e~1
IV
Similar check shall be made for 8
n
vi
3.0 ELECTRICAL CLEARANCES ON TENSION STRINGS 3.1
Electrical Clearance with Reference to Underneath of Cross-arm
Angle of Swing
Electrical Clearance Clearance =t + 0 Cos 91 Clearance =t + 0 Cos 82 -
3.2
Z Sin 91 - (B+C) ~ X1 2 Z Sin 92 - (B+C) ~ X2 2
Clearance from Tower Body·
SWING ANGLE 9, Shift deviation. Xt1
Wt1
, (
=
Projected length of Tension Insulator String upto Jumper connection for angle of
=
Cross-arm Length -
=
L, -
(Shift + 0 Sin 91 + Z Cos 91) 2 (S. Sin ~ + 0 Sin 9, + Z Cos 9,) 2 2
=
Clearance available from tower body =(Xt - Wt) Cos ~ (B+C) ~ X1 3.3
Clearance from Low Cross-Arm Tie (Inclined) Member
tance m = - - - Lm -Wmt AG
=V -
KH
= (Lm -
KG
=KH + Z Cos 9,
Y ; BH
=AG -
Z Sin 91
Lt ) + Shift + 0 Sin 91 -
AI
=AG-GI =AG -
BJ
= BH -
JH
=BH -
KG tan
oc
Z Cos 91 2
m
KH . tan
Clearance available from middle X-arm
oc m
=AE =AI Cos
oc
m- (B+C)
~
X1
· Save power for national productivity ~. MAHARASHTRA STAlE ElECTRICITY BOARD
Transmission Line Manual Chapter 4
Electrical Clearances
CONTENTS Page 4.1 Introduction
1
4.2 Minimum Ground Clearance
1
4.3 Minimum Clearance above RiverslLakes 4.4 Environmental Criteria for 800 kV Line
2
4.5 Air Clearance - General Consideration
2
4.6 Clearance and Swing Angles on Transmission Lines in India
2
4.7 Conductor Metal Air Clearances
3
4.8 Air Clearance-Analysis by CIGRE
4
4.9 Phase-to-Phase Air Clearances
5
4.10 Clearance between Conductor & Groundwire
6
4.11 Effect of Span Length on Clearance
7
4.12 Clearance at Power Line Crossings
7
4.13 Recommendation
8
ANNEXURES Annexure I
- Spacing between Conductor
11
Annexure II - Swing Angle for 800 kV Anpara - Unnao Line for Insulator Strings and Jumper
12
1
APPENDIX - Investigation Studies on Clearance and Swing Angles for Indian Power System
16
4
a
r 11
Chapter 4
ELECTRICAL CLEARANCES 4.1
Introduction
The design of a transmission line tower is distinctly classified into mechanical design and electrical 'design. The parameters which affect the design of a tower are di.§cus~d in Chapter-V, whereas loadings and mechanical design of a tower are discussed in Chapters 6 & 7 'of the Manual. In this chapter, the aspects leading to electrical design of· a tower are, therefore discussed. The electrical deslgn·oftower, infact, involves fixation of external insulation against different electrical phenomena. The extemallnsulation comprises self restoring air and solid insulation in the form of insulator strings consisting of disc insulators, mtg rod insulators etc. The electrical insulation of a tower is a function of steady state operating voltage of the syst&m and various events that occur in the system (energisation, re-energisation;-fault occurrence. and its clearance, lightning strokes etc.), For system upto and including "3b9kV voltage rating, the tower insulation is determined from the power frequency voltage and lightning impulse requirement where.as for system above300 kV rating, the power frequency and switching impulse voltages are the governing criteria.· The other factors which affect the electrical insulation are climatic conditions - altitude, relative humidity, pollution, etc. The various factors and statutory regulations which affect the electrical design of a t.ower are discussed as hereunder.
4.2 7 8
Minimum Ground Clearance
The minimum clearance above ground as per sub rule 4 of Rule 77 of I.E.Rules 1956 (latest revision) for AC system and for ± 500 kV HVDC system as adopted in India are as under: Vrltage (kV)
Nominal Highest (System)
Minimum ground clearance (mm)
66 72
132 145
220 245
400 420
--
--
800
±500
5500
6100,
7000
8800
12400
12500
To the above clearance, an additional clearance of 150 mm is added to provide for uneven ground profile and possible sagging error. , )
4.3
Minimum Clearance above Rivers/Lakes
In case of accessible frozen r'iversnakes, the minimum clearance abOve frozen riversnakes should be equal to the minimum ground clearance given in 4.2 above. '. , The minimum clearance of Power Conductor over the highest flood level in case -of ·non shall be as foliows:
navig~ble
rivers
System Voltage (kV)
Minimum clearance above higttesUloodJeveL(mm)*
72 145 245 420 800 ±500
3650 4300 5100 6400 9:400 6750
..
·(The maximum height of an obJect over the highest flood level of non-navigable rlverlll;consldClred:al·3000mm)
1
For navigable rivers, clearances are fixed in relation to the tallest mast in consultation with the concerned navigationaVport authorities.
4.4
Environmental Criteria for 800 kV Line
The Standing EHV committee of CEA (Working Group 9: Interference) have laid down the iollowing environmental criteria for 800 kV lines: Radio Interference should not exceed 50 dB for 80% of time duration during the year. For Television Interference, the minimum signal to noise ratio should be 30 dB. Audible noise should be less than 55 dB (A). Electrost~tic field at 2 m above ground below the outer most phase should be equal to or less than 10 kV/m and equal to or less than 2 kV/m at the edge of right of way. To comply with the above environmental requirements minimum ground clearance of about 15000 mm has been adopted in India for 800 kV lines.
4.5
Air Clearances - General Consideration
The air clearances applicable to transmission lines are categorised as minimum ground clearance, phase to grounded metal clearance, phase to phase clearance, clearance between power conductor and groundwire, clearance between pOwer lines crossing each other, power lines crossing telecommunication lines, railway tracks, roads etc. The phase to grounded metal clearances is a function of power frequency voltage and lightning impulse vottage in case of the transmission lines of voltage rating upto and including 245 kV and power frequency vottage and switching impulse voltage for lines above 245 kV voltage rating. The power frequency voltage is expressed in terms of service voltage or service voltage modified by events such as faults, sudden change of loads, ferranti effect, linear resonance,ferroresonance, open conductor, induced resonance from coupled circuits, etc. A line is subjected to lightning impulses due to shielding failure (direct stroke to power conductor), back flashover from tower to power conductors, vottage induction from nearby objects etc. The switching impulse voltage originates from line energisation, line reclosing, fault occurrence and clearing, switching off capacitive current (restriking effect) including line dropping and capacitor bank switching, switching of inductive currents (current chopping effect) including transformer magnetising currents and reactor switching, special switching operations including series capacitors, resonant ferro resonant circuits and secondary switching.
The air gap clearances tor phase to phase lightning impulse withstand voltages are the same as those for phase to ground lightning impuls~ withstand voltages.
4.6
Clearances and Swing Angles on Transmission Lines In India
Conductor metal clearances generally adopted in the country for transmission lines 66 kV and above are given as under:
"".1 ""VIII
.. VI'U.~:"V
(kV) 72AC
145 AC
245 AC
420 AC
Qlllijll:l
;;'Utiptml:iIOn
Swing from vertical (degree) Nil 15 30 45 60 Nil 15 30 45 60 Nil 15 30 45 60 Nil 22 44
800AC ±500 DC
Jumper
InSUIalor ~tnng Minimum clearance (mm) 915 915 760 610 610 1530 1530 1370 1220 1070 2130 1980 1830 1675
--
Nil 10 20 30
1530 1530 1070 1070
Nil 10 20
2130 2130 1675
--
---
--
--
Nil 3050 3050 20 1860 40 Discussed in the Appendix 40 3750
I
NiI*
--
--
--
<--------
Minimum clearance (mm) 915 915 610 61()
Swing from vertical (degree) Nil 10 20 30
3050 3050 1860
------->
I
1600
·V-Strings have been adopted. Notes: (i) Electrical clearance for suspension towers should be based on !single suspension strings. For road crossings, tension towers should be adopted. (ii) The details of insulator string adopted in the country for transmission lines 66 kV and above voltage are given in Chapter SP. 4.7
Conductor Metal Air Clearances
4.7.1
System VoHage
The air clearances for AC system given in document 11 (secretariat 48) of IEC referred in CiGRE document "Tower Top Geometry - WIG 22.06" issued in June "1995 and for DC system on the basis of values adopted by Power Grid for their ± 500 kV HVDC Rihand-Dadri line are given below: System VoHage (kV)
"72 145 245 420
800
<-------------- AC --------------> Air Clearance (mm) 4.7.2
190 390 650
1200 1560
±500
<------------- DC -------------> 1150
LIghtning and Switching Over-voltage
The air clearances corresponding to lightning impulse and switching over-voltages for AC system as per IEC 71-2 (1996) and for DC system as adopted by Power Grid for their ± 500 HVDe Rlhand-Dadri line are given as under.
"
System VoltagQ
Impulse withstand VoHage (kVp)
, (kV)
I
Air Clearances (mm)
Ufghtning Impluse Level
"Ligtilning': Switching \ '
.
--.
.
-
_. -
1.
2.
72AC
325 '
145AC
550 650
245AC
950 1050
,.
t I Switching Ir~plu~ Leval,'
.- - - . - ..•..•..• - - I
,
Conductor Structure
Rod Structure
Conductor Structure
Rod structure
3.
4.
5.
6.
7.
----
---
630
--
--
--
1100 1300
--
--
--
1700 1900
1900 2100
----
---
--
--
'"
420AC
1300 1425
950 1050
2400 2600
2600 2850
2200 2600
2900 3400
800AC
,1950 2100
1425 1550
3800 3900
3900 4200
4200 4900
5600 6400
±500DC
1800 ..
1000
--
--
3750
4.8
,
Air Clearance· Analysis by CIGRE
4.8.1 As a sequel to adoption of structural design based on reliability concept, CIGRE SC-22,WG06 had taken up study on tower top geometery to ascertain the swing angles of the insulator strings, air clearances, etc. for the meteorological data used for determining the structural strength. The WG based on CIGRE Publication 72 had interalia worked out air clearances corresponding to lightning and switching surges understill air,condition/small swing angle in Document "Tower Top Geometry" - June 1995 as given below. Minimum Phaseto-Earth Air Clearance (mm) ,
Nominal VoHage uR (kV)
Highest Voltage for Equipment urn (kV)
Lightning Impulse Withstand Voltage (kV)
Switching Impulse Withstand Voltage (kV)
1.
2.
3.
4.
5.
110
123
450 550
940 1130
230
245
850 950 ' 1050
----
..
---
1760 ,1970 2180
400
420
1175 1300 1425
850 950 1050
2430 . 2800 3250
500
525
1300 1425 1550
950 1050 1175
2800, 3250 3900
Values recommended for adoption are given separately.
- -- - ---- -----." .--,....... "'..-
I
1
~--
. . r-·
CIGRE Doc of June 95 adopted in ·other ·'countries .are,given Tables . A.;1 ;and i"~2. ,4i8:3
1 J J
hi
. Ie 9
The 'correlation between wind.pressure (speed) ',and'maximum ~angle :of iSWi~ Jdf.uspenslon 'strings(bdth 'r&V):adopted in.other.countries:indicates1h1lnhese;pressure·s.famtn1th8~:dJOO/o \to 70%,ofUHimate wind:pressure. :Further, '1hese'WfAd:pressures:corre'$pol'Itf'JtolllHrll'geeus :characterisedbyretum ;period :df:2·to '5 'years .againstfJOwer!frequency'Ndlt.;mmaaad1~ ;arnHightnlng/switchingsurges i!'l case of V;:strings. :If?.aJr~he·lretJuced 'a:ngle'lSf'sWI,,~~~, 'occasionally.a characteristic ,wind 'speed 'Is ':speclfied }'.COrresJi)OnCfing 'to' ;ndt1ffiI~'(over 'voRages incase 'of I,.suspenslon 'or pllot:suspension·:string.
)s
~
la ~ ~(
.
,
, I
:4:9
1Phase-lO-;Phase tArrClearances
4:9.1
'.Phase-to~phase·vertical.andhorizontal·.separation'betwsenipower:Conductors:df1thesame~
or'different circuits onthe same tower will be;estabIiShed1lY1:Onductormetal:t!teamrrae8l1scuased tn Paras 4:7& 4:8. However minimum clearances 'betweenphases ,as 'given ;inEiTiH21(t99B) are 'reproduced 'below: 4:9.1.1 Ughtning 'Impulse .,
'Standard .lightning Impulse withstand voltage (kVp)
Mlnlmum~Alr
Clearance'(mrtI)
Rod Structure
Conductor:Structme
325
630
-
450
900
550
1100
--
650
1300
.-
750
1500
.-
850
1700
16'00
950
1900
1700
1050
2100
19'00
1175
2350
22'0t)
1300
2600
:24.00
·1425
2850
.2600
1550
3100
1675
3350·
:311;'0'0
1800
3600
:3300
1950
3900
.:3600
2100
4200
3'9'00
,
~2900
,
I.
~
i
4.12.2 Power Lines Crossing Communication Lines The minimum clearance to' be maintained between a power line and a communication line, as per "Code 'of Practice for Protection of Telecommunication Lines of Crossings with Overhead Power Lines" should be ,', as follows: ",":'
,.
Nominal
66
132
220
400
Highest
72
145
245
420
800
2440
2750
3050
4480
7900
Voltage (kV) '~I .j
"(1'
Minimum clearance between power conductor crossing telecommunication line (mm)
4.12.3 Power Line Crossing Railway Tracks The minimum vertical clearance between the lowest conductor of a power line crossing the railway track as per "Regulations for Power Line Crossings of Railway Tracks· 1987" shall be as follows:
,,"
The minimum vertical clearance above rail track as al~o highest working point of the jtb when crane is deployed and the lowest point of any conductor of crossing including ground wire under condition of maximum sag.isgiven as under: . Voltage (kV) Nominal
Minimum Ciearance (mm) Highest
66 132 220 400
72 145
245 420 800
Above Rail Track
Over Crane
14,100 14,600 15,400 17,900 22,000
2,000 2,500 3,500 6,000 9,50Q
4.12.4 Power Lines Running Along or Across the Roads The minimum clearanct:: above ground for 66 kV and above voltage power lines running along or across • the road shall be 6,1 m as per Rules 77 of I.E, Rules 1956 provided the requirement stipulated in Sub·Rule . (4) of Rule 77 of IE Rules 1956 is met. . ~
As per electrostatic field effect of EHV transmission lines, the minimum clearance for line passing over the' road shall be corresponding to field gradient of 10 kV/m, It should not permit a short circuit current more than 5 rnA through an individual when touching a vehicle standing below the line. .
4.13
Recommendation
4.13.1 Air clearances and swing angles for various system voltage ratings are recommended as under:
~ ,
.
,
System voltage (kV)
Swing from vertical (degree)
145 AC
Jumper
Single SuspenSion Insulator String Minimum clearance (mm)
Swing from vertical (degree)
15 30 45 60
915 760 610 610
10 20 30
Nil
1530
Nil
1530
245 AC
30 45 60
1370 1220 1070
20 30
1070 1070
Nil
2130 1980 1830 1675
Nil 10
2130 2130 1675
3050 3050 1860
Nil
5600/5100 4400 1300
Nil
15 30 45 60 400 AC
Nil
22 44
20
20 40
3050 3050 1860
800 AC Zones 1&
Nil
II
22 45
Zones III &IV
Nil
27 55
Zones V & VI
Nil 30
60
15 30
5600/5100 4400 1300
20 40
5600/5100
Nil
4400 ' 1300
22 45
Nil
5100 4400 1300 5100 4400 1300 5100 4400 1300
4.13.2 The spacing between conductors for,long spans shall be established from the following formulae: Vertical Clearance (,-1)
0.75
Vf.,s +--i~-
+
V
T5U
Horizontal Clearance (m)
Where
= = =
Sag at 75" C Length of Insulator String in metres. Line Vo~age in kV
60 01 .~ ~
-i VI I //0
1----- ---- ---50
en L..
~
L
40
E
/
~I
Nominal Voltage : 500 k V "2Conductor : ACSR 410mm x4 Insulator Strings: 320mm x 26pc s. double strain
:
I
Depth of Jumper: 5,000 mm
I I
Catenary Angle :
I
.
::J ..."
.... 30
o
!
/1
L
QI
g' 20
~
~-----
10
l/
o
o
-Ii
V
10
20
30
40
OCI
+oc2: 5°
Without reinforcement
-
With reinforcement wire And reinforcement spacer
----_.-.-
50
Mean wind speed during 10 minutes [m/sec] Figure I : Swing characteristics of jumper conductor based on test carried out in Japan.
F:LXSin~12
r-=;
o o
0
0
0
Where.
(a) Suspension Insulator Strings
L. Length of insulator strings Line deviation angle (b) Jumper (wi thout pilot Suspension Insulator
e.
C:. r:nn c. \
Germany
Austria
Belgium
O. 75Jf + 1 k + ~m (Vertical)
O.62Jf+l k
+~m (Horizontal)
France
U.S.A.
O. 75V+3.26~ inch
Poland
Sweden
6.5~+O.7vcm
Czechoslovakia
Canada In which f = 1+40 =
1k
•
La
VR
.=
"5
=
V ~
= =
25+V+7~cm .
Max. Sag Sag at 40° C Length of Insulator String (assumed as 4 m) VoHage in kV Actual span in m limited to 450 m Reference span in m (50 m) Reference Voltage in kV (5 kV) Sag at 15° C
.. ." • ,
'
i
I I
rf~,
11.'.-
,
«! •• l t:
, c: fi .~
'1 fc'
t:
,; ~.: .. ',
'-:;
f: C'
!
tJi> .1
G
• • •.
•• •• •
'•.
Transmission Line Manual Chapter 5
Design Parameters
i..
CONTENTS Page
5.0 Abstract 5.1 Transmission Voltage 5.2 Number of Circuits 5.3 Climatic Conditions and Ecological Consideration 5.4 Environmental . .
5.5 Conductor 5.6 Earth Wire 5.7 Insulator Strings
2 2 11 11
12 13
17
-
5.8 Span
,, .~
s
')
COl T~I I
I
Design Parameters 5.0
ABSTRACT
The design of transmission line towers is entirely dependent on the selection of correct data/parameters. A good tower designer should accumulate all necessary design parameters before starting the design work. This chapter describes the design parameters required for developing a transmission line tower design. These design parameters should be correct and authentic in nature to ensure· reliability of transmission line under given conditions.
5.1
Transmission Voltage
This is very important parameter. All the electrical parameters such as air gap clearance, phase to phase clearance, ground clearance etc. are fully dependent on the voltage level. The power is transmitted either through A.C. System (alternating current) or through D.C. system (Direct Current) depending upon the requirement of power system of a particular region or country as a whole. In India the following transmission voltages have been standardised for transmitting the power :
A.C. System (i). (ii) (iii) (iv) (v) (vi)
66KV 110KV 132KV 220KV 400KV 800KV
D.C. System (i) .+/-500KV
For indigenous development of HVDC technology, Govt. of India had approved HVDe Research and Development proposal in Nov. 1981 and action plan in Nov. 1982 for taking the R&D project on an actual line to enhance the power level. APSEB and MPEB had offered 220KV DIC Lower Sileru (A.P) Barsoor (M.P) line for the experimental project. The HVDC Steering Committee in Oct. 1983 approved National HVDe project (NHVDC) to be taken in 3 stages. Stage I
1OOMW, + 100KV monopole
Stage II
200MW, + 200KV monopole
Stage III
400MW, + 200KV bipole
The National HVDC Stage I was approved by Government in Oct. 1984 for establishing a 100MW, ± 100 KV HVDC, 6 pulse monopole link between Lower Sileru and Barsoor by converting one circuit of 220KV D/C Lower Sileru-Barsoor line. The Stage I has been commissioned in Oct. 1991 and is in operation. The Stage II for uprating Stage I to 200 MWj +200KV, 12 pulse monopole has been approved by the Govt. in Sept. 1993 and scheduled to be commissioned by the end of 1997.
2
Design Parameters
5.2
Number of Circuits
The transmission line can be classified into three categories depending on the number of circuits. Each circuit consists of three phases. However, each phase may further consist of single, twin or multiple bundle of conductors. The three classifications based on the number of circuits are :(a)
SINGLE CIRCUIT
(b)
DOUBLE CIRCUIT
(c)
MULTI CIRCUITS (i)
Single Circuit : The transmission line which carries only one circuit.
(ii)
Double Circuit : The transmission line which carries two circuits.
(iii)
Multi Circuit: The transmission line which carries more than two circuits.
However, single circuit and double circuit transmission lines are popular throughout the world. Some of the utilities of the world have constructed multi circuit transmission lines also to avoid Right of Way problems in Urban areas but the number of such lines are very less as the multiple circuit lines are not advisable from the maintenance & reliability point of view. Some of the utilities of the world have constructed multivoltage lines which have more than two circuit of different voltage levels. Wherever Right of Way constraints are foreseen, multiple circuit and multivoltage lines are preferable. 5.3
Climatic Conditions
The reliability of a transmission system is largely dependent on the accuracy of the parameters related to climatic conditions considered for design. The design of tower will vary with variation in climatic conditions. The following are the main climatic parameters which play vital role in developing design of transmission line towers :1.
Wind
2.
Temperature
3.
Isokeraunic level
4.
Seismic Intensity
5.
Ice formation.
5.3.1 Wind
~:
5.3.1.1 The Wind speed have been worked out for 50 years return period based on the -tlPto-date wind data of 43 dynes pressure tube (DPA) anemograph stations and study of other related works available on the. subject since 1964. The basic wind speed data have been published by Bureau of Indian Standards in IS : 875-1988 in active cooperation with In9ian Meteorological Department as shown in Figure 1. This map represents basic wind speed based on peak gust velocity averaged over a short time interval of about 3 seconds and corresponds to 10m height above mean ground level in terrain Category-2 for 50 yrs. return period. Based on the wind speed map the entire country has been divided into six wind zones ... :........... v , .. :.. ,.1
"'''' ........,.1
,,* r::.r::.m/" ....,.
~n~ min win~ C!noorl nf ':l':lm/c:.~('
R~c:.i('
winn c:.nAAn fnr thA
TABLE I Wind Zone
Basic Wind Speed (m/sec)
1 2
33 39
3
44
4 5
47 50
6
55
,
NOTE : In case the line tranverses on the border of wInd zones, the hIgher wInd speed may be considered.
5.3.1.2 Reference Wind Speed VR
It is extreme value of wind speed over an average period of 10 minutes duration and is to be calculated from basic wind speed 'vb' by the following relationships:VR = vb/ko Where : Ko is a factor to convert 3 seconds peak gust speed into average speed of wind during 10 minutes period at a level of 10 meters above ground. Ko is to be taken as 1.375. 5.3.1.3 Design Wind Speed, Vd
Reference wind speed obtained in 5.3.1.2 shall be modified to include the fo.llowing effects to get the design wind speed : (i)
Risk Coefficient, K,
(ii)
Terrain Roughness coefficient, K2
It is expressed as follows :Vd = VR' K,. ~
5.3.1.4 Risk Coefficient K1
Table 2 gives the values of Risk Coefficient K, for different wind zones for three Reliability Levels. TABLE 2 Risk Coefficient K1 for Different Reliability Levels and Wind Zones Reliability Level
1
Coefficient K, for wind zones : 5 4 2 3
1(50 yrs. return period)
1.00
1.00
1.00
1.00
1.00
1.00
2(150 yrs. return period)
1.08
1.10
1.11
1.12
1.13
1.14
3(500 yrs. return period)
1.17
1.22
1.25
1.27
1.28
1.30
6
Design Parameters
4
5.3.1.5 Terrain Roughness Coefficient, K2 Table 3 gives the values of coefficient ~ for the three categories of terrain roughness corresponding to an average 10 minutes wind speed. TABLE 3 Terrain Roughness Coefficient Terrain Category Coefficient
~.
~
1
2
3
1.08
1.00
0.85
5.3.1.6 Terrain Categories (a)
Category 1 - Coastal areas, deserts and large streches of water.
(b)
Category 2 - Normal cross country lines with very few obstacles.
(c)
Category 3 - Urban built up areas or forest areas.
NOTE: For lines encountering hills/ridges, value of K2 will be taken as next higher value. 5.3.1.7Design Wind Pressure Pd The design wind pressure on towers, conductors and insulators shall be obtained by the following relationship :Pd
= 0.6 Vd2
Where Pd = design wind pressure in N/m 2 and Vd = Design wind speed in m/s. Design wind pressure Pd for all the three Reliability levels and pertaining to six wind zones and the three terrain categories have been worked out and given in· Table 4. TABLE 4 Design Wind Pressure Pd, in N/m2 (corresponding to wind velocity at 10m height) Reliability Level
Terrain Category
1
1 2 3
403 346 250
563 483 349
717 614 444
818 701 506
925 793 573
1120 960 694
2
1 2 3
470 403 291
681 584 422
883 757 547
1030 879 635
1180 1010 732
1460 1250 901
1120 960
1320 1130
1520 1300
1890 1620
1
Wind pressure Pd for wind zones 4 5 2 3
6
)
3
1 2
552 473
838 718
(A)
Wind Load on Tower
In order to determine the wind load on tower, the tower is divided into different panels having a height 'h'. These panels should normally be taken between the intersections of the legs and bracings. For a lattice tower, the wind load Fwt in Newtons, for wind normal to a face of tower, on a panel height 'h' applied at the centre of gravity of this panel is : Fwt = Pd. Cdt • Ae. GT Pd = Design wind pressure, in N/M2 Cdt = Drag Coefficient pertaining to wind blowing against any face of the tower. Value of ~dt for the different solidity ratios are given in Table 5. Ae = Total net surface area of the legs and bracings of the panel projected normally on face in m2. (The projections of the bracing elements of the adjacent faces and of the plan-and-hip bracing bars may be neglected while dete-rmining the projected surface of a face). GT = Gust Response Factor, perpendicular to the ground roughness and depends on the height above ground. Values of GT for the three terrain categories are given in Table 6. TABLE 5 Drag Coefficient, Ccit For Towers
. Solidity Ratio'"
Drag Coefficient, Cdt
Upto 0.05 0.1 0.2 0.3 0.4 0.5 and above
)'3.6 3.4 2.9 2.5 2.2 2.0
Note : Intermediate values may be linearly Interpolated.
"'Solidity ratio is equal to the effective area (projected area of all the individual elements) of a frame normal to the wind direction divided by the area enclosed by the boundary of the frame normal to the wind direction. TABLE 6 Gust Response Factor for Towers (GT) and for Insulators GI)
Height above ground m Upt010 20 30 40 50 60 70 80
Values of GT and GI fo(Aerrain Categories 1
1.70 1.85 1.96 2.07 2.13 2.20 2.26 2.31
Note : Intermediate values may be Interpolated.
fl 1.92 2.20 2.30 2.40 2.48 2.55 2.62 2.69
3
2.55 2.82 2.98 3.12 3.24 3.34 3.46 3.58
6
Design Parameters
(B)
Wind Load on Conductor and Groundwire
The load due to wind on each conductor and ground wire, Fwc in Newtons applied at supporting point normal to the line shall be determined by the following expression : Fwc = Pd. L. d. Gc. Cdc Where: Pd = Design wind pressure in N/m2; L
= Wind span, being sum
of half the span on either side of supporting point, in
metres. d
= Diameter of conductor/groundwire, in metres.
Gc = Gust Response Factor which takes into account the turbulance of the wind and the dynamic response of the Conductor. Values of Gc are given in Table 7 for the three terrain categories and the average height of the conductor above the ground. Cdc
= Drag coefficient which
is 1.0 for conductor and 1.2 for Groundwire.
Note : The average height of conductor/groundwire shall be taken upto clamping point on tower less two third the conductor/groundwire sag at minimum temperature and no wind.
The total effect of wind on bundle conductors shall be taken equal to the sum of the wind load on sub-conductors without accounting for a possible· masking effect of one of the subconductors on another. TABLE 7 Values of Gust Response Factor Gc. for Conductor/G-Wires
Terrain Category
Height Values of Gc for conductor of span, in m above Upto: ground, m 200 300Y\) 400 700 500 600
800
&above
1. Upto
10 20 40 60 80
1.70 1.90 2.10 2.24 ·2.35
1.65 1.60 1.871-1'5'1.83 2.04 :],·ov2.00 2.18 2.12 2.25 2.18
1.56 1.79 1.95 2.07 2.13
1.53 1.75 1.90 2.02 2.10
1.50 1.70 1.85 1.96 2.06
1.47 1.66 1.80 1.90 2.03
~.
10
1.78 1.73 2.041-:(\0.\1.95
1.69 1.88
60 80
1.83 2.12 2.34 ·2.55 2.69
1.60 1.80 2.05 2.20 2.32
1.55 1.80 2.02 2.17 2.28
10 20 40 60 80
2.05 2.44 2.76 2.97 3.19
1.77 2.06 2.38 2.56 2.73
1.73 2.03 2.34 2.52 2.69
3.
!~
2.46 2.56
2.37 l.! \'lJ2.28 2.48 2.41
1.65 1.84 2.08 2.23 2.36
1.98 2.35 2.67 2.87 3.04
1.93 2.25 2.58 2.77 2.93
1.83 2.10 2.42 2.60 2.78
./
2~2Z2·1~{2.20:L'l~2.13
1.88 2.15 2.49 2.67 2.85
\"'1
nlllu L.UClU
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.:nnngs
Wind load on insulator strings 'Fwi' shall be determined from the attachment point to the centre line of the conductor in case of suspension tower and upto the end of clamp in case of tension tower, in the direction of the wind as follows: Fwi = 1.2 . Pd . Ai . Gi Where: Pd
= Design Wind pressure in
Ai
= 50 Per cent of the area of Insulator string projected on a plane parallel to the
N/m2
longitudinal axis of the string (1/2 x diameter x length). NOTE : Length of Insulator shall be co'hsidered as follows : Suspension Insulator!
from the centre point of conductor to the connection point of Insulator to the tower. Tension Insulator:
End of tension clamp to the connection point of insulator to the tower. Gi =
Gust Response Factor, perpendicular to the ground roughness and depends on the height above ground. Values of Gi for the three terrain categories are given in Table 6.
In case of multiple strings no masking effect shall be considered.
5.3.2 Temperature
To evolve design of tower, three temperatures i.e. Max. temperature, min. temperature and everyday temperature are very important. Tower height as well as sag and tension calculation of conductor and earthwire varies with the change in above three temperatures. The temperature range varies for different parts of India under different sea.sonal conditions. The absolute max. and min. temperatures which may be expected in different localities in country are indicated on the map of India in Fig 2 and Fig 3 respective.ly. The temperature indicated in these maps are the air temperature in shade. The max. conductor temperatures may be obtained after allowing increase in temperature due to solar radi.ation and heating effect due to current etc. over the absolute max. temperature given in Fig 2. After giving due thought to several aspects such as flow of excess power in emergency during summer time etc. the following three designs temperatures have been fixed : (a) (b) (c) (d)
(e)
Max. temperature of ACSR conductor = 75 deg.c Max. temperature of AAAC conductor = 85 deg.c Max. temperature of earthwire = 53 deg.c. Min. temperature (ice free zone) =- 5 deg C to +10 deg. c (depends on location of the trans. line of however Goc widely used in the country) a Everyday Temperature 3). C (for most parts of the country).
For region with colder climates (-5 deg.c or below) the respective Utility will decide the everyday temperature. 5.3.3 Lightning Consideration for Tower Design
As the overhead transmission lines pass through open country, they are' subjected to the effects of lightning. The faults initiated by lightning can be of following three types :
Design Parameters,
8
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Design Parameters
10
(i)
Back flash over: When lightning strikes on a tower or on the earthwire near the tower which raises the tower potential to a level resulting in a discharge across the insulator string.
(ii)
Midspan flash over: When a lightning strikes on earthwire raising local potential of the earthwire such that a breakdown in the air gap between earthwire and phase conductor results.
(iii)
Shielding failure: When lightning strikes on the phase conductor directly resulting in a flashover across the insulator string. *'
The above type of faults can be minimised by suitably choosing the shielding angle and keeping the tower footing resistance at the minimum. Lightning is a very unpredictable phenomenon. Moreover not enough data are available, at present. to treat them in statistioal technique. The_ only data available are the isokeraunic level; i.e. annual number of thunder storm days for a particular area; but it does not give information on the intensity of strokes. In view of the above fact, following shield angles are provided in EHV line towers as per present practice in the country.
Voltage Level
Shield Angle
66KV
: 30 DEG
110/132KV
: 30 DEG
220KV
: 30 DEG
400KV
Single Ckt. (Horizontal Configuration) Outer Ph.
: 20 DEG
Inner Ph.
: 45 DEG
400KV
Single Ckt. (Vertical Configuration)
: 20 DEG
400KV
Double Ckt.
: 20 DEG
Single Ckt. (Horizontal Configuration) Outer Ph
: -15 DEG
Inner Ph
: 45 DEG
- 800KV
5.3.4 Seismic Consideration The transmission line tower is pin jointed light structure comparatively flexible and free to vibrate and max. wind pressure is the chief criterion for the design. Concurrence of earthquake and max. wind condition is unlikely to take place and further siesmic stresses are considerably diminished by the flexibility and freed\),,", f~~ vibration of the structure. This assumption is also in line with recommendation given in cl. no. 3.2 (b) of IS : 1893-1984). Seismic considerations, therefore. for tower design are ignored and have not been discussed here. However in regions where earthquakes are experienced, the earthquake forces may be considered in tower -
_ . . . . . _ ..... " . 'UII
gl lOW
"',"vlv~l"al
,",UII::tIUt:1 cUIUIi
. The transmission line corridor requirement for different voltage lines are as follows :Voltage Level (KV)
Corridor Requirement (MetfffS)
66 110 132 220 400 800
18 22 27 35 52 85
While deciding tower and conductor configuration of Transmission Lines at 400KV and above, the interference level should be maintained within the following limits :(i)
RI should not exceed 50 dB at 80% of the time during the year.
(ii)
TVI - The minimum signal to noise ratio should be 30 dR
(iii)
Audio noise level for 800KV system should be less than 55 dB (A).
(iv)
Electrostatic field should be less than 10 KV/m below the outermost phase (2m above the ground) and less than 2 KV/m at the edge of the right of way.
PTCC :650
1.
Maximum value of induced electromagnetic voltage for fault duration equal to or less than 200 ms.
volts
2.
Maximum value of induced noise (noise interference) To be taken cognizance if noise is persistent
microvolts
5.5
Conductor
2000 (measured)
Conductors normally used for 400KV and 220 KV lines are given below with their electrical and mechanical properties : 5.5.1
Voltage Level Code Name of Conductor No. of conductor/Phase StrandinglWire diameter Total sectional area Overall diameter Approx. Weight Calculated d.c. resistance at 20 deg. Min. UTS Modulus of elasticity Co-efficient of linear expansion Max. allowable temperature
400KV ACSR "MOOSE" Two (Twin Bundle) 54/3.53mm AL+7/3.53mm steel
&
597 mm2 31.77mm 2004 Kg/Km . 0.05552 ohm/km 161.2KN 7034Kg/mm2 19.30x10-6/deg. t: 75 deg.C
Design Parameters
12
5.5.2 Voltage Level Code Name of Conductor No. of conductor/Phase Stranding/Wire diameter Total sectional area Overall diameter Approx. Weight Calculated d.c. resistance at 20 deg. fi Min. UTS Modulus of elasticity Co-efficient of linear expansion Max. allowable temperature
220KV ACSR "ZEBRA" ONE 54/3.18mm AL+7/3.18mm 484.5mm2 28.62mm 1621 KglKm 0.06915 ohm/km 130.32 KN 7034Kglmm 19.30x10-6/deg. G 75 deg. G
5.5.3 Voltage Level Code Name of Conductor No. of conductor/Phase Stranding/Wire diameter Total- sectional area Overall diameter Approx. Weight Calculated d.c. resistance at 20 deg.C Min. UTS Modulus of elasticity Co-efficient of linear expansion Max. allowable temperature
1321110KV ACSR "Panther" ONE 30/3mm AL+7/3mm St. 261.5mm2 21.00mm 974 Kglkm 0.140hm/km 89.67 KN 8155Kglmm 17.80x10-6/deg. G 75 deg.C
5.5.4 Voltage Level Code Name of Conductor No. of conductor/Phase Stranding/Wire diameter Total sectional area Overall diameter Approx. Weight Calculated d.c. resistance at 20 deg. C. Min. UTS Modulus of elasticity Co-efficient of linear expansion Max. allowable temperature
66KV ACSR "Dog" One 6/4.72 mm AL+7/1.57mm St. 118.5mm2 14.15mm 394 KglKm 0.281 ohm/km 32.41 KN 7747Kglmm 19.80x10-6/deg. C 75 deg.C
5.6
Earth Wire
The earthwire to be used for transmission line has been standardised. Continuously run galvanised steel earthwire~.!rA~ to be used for lines, earthed at every tower points. The properties of the earthwire~{)(fkv and 220~v~~as follows:5.6.1 Voltage Level Material of earthwire , No. of continuous earth wires
400 KV Galvanised Steel Two
I otal
sectional area Overall diameter Approx. Wt. Calculated d.c. resistance at 20 deg. C Minimum UTS Modulus of elasticity Co-efficient of linear expansion Max. allowable temperature 5.6.2 Voltage Level Material of Earthwire No. of Earthwires Standing/wire diameter Total sectional area overall diameter Approx. wt. Calculated d.c. resistance at 20 deg. 'c Minimum UTS Modulus of elasticity co-efficient of linear expansion Max. allowable temperature. 5.7
73.65 mm"
10.98 mm 583 Kg/Km 2.50hms/Km 68.4 KN 19361 kg/mm2 11.5x10-6/deg.C. 53 deg. c: 220 KV, 132 KV, 110KV, 66KV Galvanised Steel one 7/3.15 mm 54.55 mm2 9.45 mm 428Kg/Km 3.375 ohmslKm 5710 Kg 19361 kg/mm2 11.5x1 O-s/deg. ~ 53 deg. ,
Insulator Strings The following type of insulator strings are generally used on transmission lines:
5.7.1
400 KV INSULATORS
S.No. Type of String
1.
Single Suspn. 'I' string
Tower Type
Standard tangent type tower. In case of single ckt. horizontal configuration 'I' suspension strings are generally used "on two outer phases
Size of The DISC (DIA X Spacing) (mm)
No. of Standard Discs
Electro Mechanical Strength of Insulator Disc (KN)
Mechanical Strength of The Complete String (KN)
255/280 x145
1x23
120
120
Design Parameters
14
S.No. Type of String
Tower Type
2.
Single Suspn. 'I' pilot
255/280 Large deviation x145 angle towers for restraining the jumper coming closer to the tower body. Also used on trans-position towers
3.
Single Suspn. 'V' string
.4.
Double Suspn. 'I' string
No. of Standard Discs
Electro Mechanical Strength of Insulator Disc (KN)
Mechanical Strength of The Complete String (KN)
1x23
120
120
255x145
2x23
90
12ll
255/280 x145
2x24
120
2x120
Size of The DISC (DIA X Spacing) (mm)
Middle phase of horizontal· configuration single ckt. tower River crossing or any other type special suspn tower
5.
Single tension
Transposition Arrangement
280/170 OR 245/170
1x24
120
120
6.
Double tenssion
Tension Towers
280/170 145/170
2x23
160
160
5.7.2 220 KV INSULA TORS 1.
Single 'I' Suspn. string
Standard tangent type tower
255x145
130r14
70
70
2.
Single Suspn. pilot string
Large deviation 255x145 angle towers for restraining the Jumper coming closer
130r14
70
70
tn tho
S.No. Type of String
Tower Type
Size of The DISC (DIA X Spacing) (mm)
No. of Standard Discs
Electro Mechanical Strength of Insulator· Disc (KN)
Mechanical Strength of The Complete String (KN)
255x145
2x14
70
2x70
3.
Double Suspn. string
River X-ing or any other type special suspension tower
4.
Single tension string
All type of 255x145 angle tower including Dead end, section & transposition towers
140r15
120
120
5.
Double tension string
River X-ing or any other special tension tower
255x145
2x15
120
240
5.7.3 132 KV INSULATORS 1.
Single II' Suspn. string
standard tangent type tower
255x145
9
45
45
2.
Single Suspn. pilot string
Large deviation 255x145 angle towers for restraining the jumper coming closer to the tower body
9
45
45
3.
Double Suspn. string
River X-ing or any other type special suspension tower
2x9
45
2x45
4.
Single' tension string
All type of 255x145 angle tower including Dead end, section & transposition towers
10
70
70
255x145
Design Parameters
16
S.No. Type of String
Tower Type
Size of The DISC (DIA X Spacing) (mm)
No. of Standard Discs
Electro Mechanical Strength of Insulator Disc (KN)
Mechanical Strength of The Complete String (KN)
5.
River X.ing or any other special tension tower
255x145
2x10
70
140
Double tension string
5.7.4 110KV INSULA TORS
1.
Single 'I' Suspn. string
Standard tangent type tower
255x145
8
45
45
2.
Single Suspn. pilot string
Large deviation 255x145 angle towers for restraining the jumper coming closer to the tower body
8
45
45
3.
Double Suspn. string
River X-ing or any other type special suspension tower
2x8
45
2x45
4.
Single tension string
All type of 255x145 angle tower including Dead end section & Transposition towers
9
70
70
5.
Double tension string
River X-ing or any other special tension tower
255x145
2x9
70
2x70
255x145
5
45
45
255x145
5.7.5 66 KV INSULA TORS
1.
Single 'I' Suson.
Standard tanaent
S.No. Type of String
Tower Type
No. of Standard Discs
Electro Mechanical Strength of Insulator Disc (KN)
Mechanical Strength of The Complete String (KN)
2.
Single Suspn. pilot string
Large deviation 255x145 angle towers for restraining the jumper coming closer to the tower body
5
45
45
3.
Double Suspn. string
River X-ing or any other type special suspension tower
255x145
2x5
45
2x45
4.
Single tension string
All type of angle tower including Dead end & section towers
255x145
6
45
45
5.
Double tension string
River X-ing or any other special tension tower
255x145
2x6
45
2x45
5.8
Span
Size of The DISC (DIA X , Spacing) (mm)
~
5.8.1 Design Span
Normal design span for various voltage transmission lines considered are as follows. Voltage
Normal sp,an
800 400 220 132 110 66
400,450m 400 m 335, 350, 315, 325, 315, 325, 240, 250,
KV KV KV KV KV KV
375 335 335 275
m m m m
5.8.2 Wind Span: The wind span is the sum of the two half spans adjacent to the support under consideration. For plain terrains this equals. to normal rulling span. 5.8.3 Weight Span: The weight span is the horizontal distance between the lowest point of
the conductors on the two adjacent spans. For design of towers the following weight spans are generally considered :
Design Parameters
18
400KV LEVEL I!rrlin!tower type
. permissible Weight Span (mts) NormDI condition Max. Min.
(a)
Plain Terrain Suspension SmalVMedium Angle Large angle
(b)
Broken wire Condilion Min. Max.
600 600 600
200 0 0
360 360 360
100 -200 -300
600 1000
200 - 1000
360 - 600
100 - 600
Hilly Terrain Suspension SmalVMedium/Large anlge
220 KV LEVEL (a)
. Plain Terrain Suspension Small/Medium Angle Large angle
(b)
525 525 525
200 0 0
315 315 315
100 - 200 - 300
525 1000
200 - 1000
315 600
100 - 600
Hilly Terrain Suspension SmalVMedium/Large angle
1321110 KV LEVEL
(a)
Plain Terrain Suspension Small/Medium Angle Large angle
(b)
488 488 488
195 0 0
195 195 195
104 - 200 - 300
488 960
208 - 960
192 576
104 - 576
Hilly Terrain Suspension SmalVMediurnlLarge angle
66 KV LEVEL (a)
Plain Terrain Suspension SmalVMediurnl Large/angle
(b)
Hilly Terrain
375 375
163 0
150 150
75 - 150
375 750
163 - 750
150 450
75 - 450
•
Suspension SmalVMediumlLarge angle
,I
t:
Transmission Line Manual
.
, ,
. .
Chapter 6
Loadings ,
.
'.
I.
;
,
.
CONTENTS Page 6.1 Introduction 6.2 Requirements of Loads on Transmission Lines 6.3 Nature of Loads 6.4 Loading Criteria 6.5 Transverse Loads (TR) - Reliability Condition (Normal Condition)
2
6.6 Transverse Loads {TS) - Security Condition
4
6.7 Transverse Load (TM) during Construction and Maintenance - Safety Condition
4
6.8 Vertical Loads (VR) - Reliability Condition
4
6.9 Vertical Loads (VS) - Security Condition
5
6.10 Vertical Loads during Construction and Maintenance (VM) - Safety Condition
5
6.11 Longitudinal Loads (LR) - Reliability Condition
5
6.12 Longitudinal Loads (LS) - Security Condition
5
6.13 Longitudinal Loads during Construction and Maintenance (LM) - Safety Condition
5
6.14 Loading Combinations under Reliability, Security and Safety Conditions
6 '
6.15 Anti-cascading Checks
6
6.16 Brokenwire Condition
6
6.17 Broken Limb Condition for 'V' Insulator String
6
6
tl 0:
.,
Q •
6
CHAPTER VI age
LOADINGS
6.1 INTRODUCTION
4
Tower loading is most important part of tower design. Any mistake or error in the load assessment will make the tower design erroneous. Various types of loads are to be calculated accurately depending on the design parameters. In the load calculation the wind plays a vital role. The correct assessment of wind will lead to proper load assessment and reliable design of tower structure.
4
6.2 REQUIREMENTS OF LOADS ON TRANSMISSION LINES
5
Overhead transmissio~ lines are subjected to various loads during their life span which are classified into three distinct categories:-
5
(a) Climatic loads related to reliability requirements.
5 5
(b) Failure containment loads related to security requirements.
5
(c) Construction and maintenance loads related to. safety requirements.
6
6.2.1 Reliability Requirements-Climatic Loads under Nonnal Condition
towers Shall be checked for anti-cascading loads for all conductors and earthwires broken in the same span. 6.2.3 Safety Requirements - Loads during Construction and Maintenance . As an important and essential requirement, Construction and Maintenance Practices should be regulated to eliminate unnecessary and temporary loads which would otherwise demand expensive permanent strengthening of Towers.
6.2.3.1 Loads during Construction These are the loads imposed on tower during the construction of transmission line.
6.2.3.2 Loads during Maintenance These are the loads imposed on tower during the maintenance of transmission line. 6.3 NATURE OF LOADS 6.3.1 Transverse Loads (T)
6.3.1.1 Wind load on tower structure, conductor, ground-wire and insulator strings.
6.2.1.1 Wind Loads (Non-Snowy Regiens).
6.3.1.2 Component of mechanical tension of condu.ctor and ground-wire.
6
6.2.1.2 Wind Loads with Ice (Snowy Regions).
6.3.2 Vertical Loads (V)
6
6.2.1.3 . Wind loads without Ice (Snowy Regions).
6
Transmission lines in snowy regions will be dealt with in a separate document.
6.3.2.1 baads due to weight of each conductor, ground-wire \ based on appropriate weight span,weight of insulator strings and fittings.
6.2.2 Security Requirements - Failure Containment Loads under Broken Wire Condition
6.3.2.2 Self-weight of structure. 6.3.2.3 Loads during construction. and
main~nance.
6.2.2.1 Unbalanced Longitudinal Loads and Torsional Loads. 6.3.3 Longitudinal Loads (L) due to Broken Wires Unbalanced Horizontal loads in longitudinal direction All towers should have inherent strength for resisting due to mechanical tension of conductor andlor groundwire the Longitudinal and Torsional Loads resulting from during broken wire condition. breakage of specified number of conductors andlor ..6.4 LOADING CRITERIA earthwire. Loads imposed on tower due to action of wind are 6.2.2.2 Anti-Cascading Loads calculated under the following climatic criteria: Failure of items such as insulators, hardware joints etc. Every day temperature and design wind pressure. as well as failure of major components such as towers, Criterion I foundations and conductors may result j., cascading Criterion n Minimum temperature with 3.6% of design condition. In order to prevent the cascading failures angle wind pressure.
2
Loadings
6.5 TRANSVERSE LOADS (TR) - RELIABILITY CONDITION (NORMAL CONDITION)
Cdc = Drag Coefficient which is 1.0 for conductor and 1.2 for ground-wire.
6.5.1 Wind Load on COllductor/G round-Wire
Gc
The load due to wind on each conductor and ground-wire normal to the line applied at supporting point shall be determined by the following expression:Fwc
=Pd x L x d x Gc x Cdc
where Fwc Pd L
d
= =
= Gust response factor which takes into account the turbulance of the wind and the dynamic response of the conductor.
Values of Gc for three terrain categories and different height of the conductor/groundwire above Ground Level are given in Table-I. The average height will be taken upto the clamping point of top conductor/groundwire on tower less two-third the sag at minimum temperature and no wind,
Wind load in Newtons
6.5.2 Wind Load on Insulator String Design wind pressure in N/nt (see 5.3.1. 6 6.5.2.1 Wind load on insulator strings shall be determined of coapter -5). from the attachment point to the centre-line of the conductor = Wind span in metres in case of suspension tower and upto the end of clamp in = Diameter of conductor/groundwire In case of tension tower, in the direction of wind as follows:metres.
TABLE ·1 Values of Gust Terrain
Height
Category
above ground
Respon~e
Factor Gc for Conductor/Groundwire Values of Gc for conductor of span in metres upto
200
300
400
500
600
700
. & above
(metres) 1.
2.
3.
Upto
Up to
Upto
. Noh!:
800
10
1.70
1.65
1.60
1.56
1.53
1.50
1.47
20
1.90
1.87
1.83
1.79
1.75
1.70
1.66
40
2.10
2.04
2.00
1.95
1.90
1.85
1.80
60
2.24
2.18
2.12
2.07
2.02
1.96
1.90
80
2.35·
2.25
2.18
2.13
2.10
2.06
2.03
10
1.83
1.78
1.73
1.69
1.65
1.60
1.55
20
2.12
2.04
1.95
1.88
1.84
1.80
1.80
40
2.34
2.27
2.20
2.13
2.08
2.05
2.02
60
2.55
2.46
2.37
2.28
2.23
2.20
2.17
80
2.69
2.56
2.48
2.41
2.36
2.32
2.28
10
2,05
1.98
1.93
1.88
1.83
1.77
1.73
20
2.44
2.35
2.25
2.15
2.10
2.06
2.03
40
2.76
2.67
2.58
2.49
2.42
2.38
2.34
60
2.97
2.87
2.77
2.67
2.60
2.56
2.52
80
3.19
3.04
2.93
2.85
2.78
2.73
2.69
(i) -. Fnr lntprtnArI:'lt.a.
'co_nft
.r .... l .. __
5 to\\ .r
--.C r". __ 1I. n ____
gravity of the panel is:-
Fwi = Pd x Ai x Gi x Cdi
Fwt = Pd x Cdt x Ae x GT
where where Fwi = Wind load in Newtons Pd = Design wind pressure in N/sq. m.
Fwt = Wind Load in Newtons
Ai
Pd
= 50% area of insulator string in sq.m.
projected on a plane which is parallel to the !o~gitudinal axis of the string. Gi
Cdt
any fac~ of the tower. Value of Cdt for the different solidiLY ratios are given in Table - 3.
= Gust response factor depending upon
terrain category and height of insulator attachment above ground. Values of Gi for the three Terrain Categories are given in Table-2.
Ae
= Total
y
= In single ckt horizontal configuration towers, a part
Cd) = Drag coefficient of insulator is taken as 1.2 TABLE - 2
= Design Wind Pressure in N/m2 = .Drag Co-efficient pertaining to wind blowing against net surface area of the legs and bracings including x- arm members and redundants of the panel projected normally on windward face in sq.m. (The projections of the bracing elements of the adjacent faces and ofthe 'plan' and 'hip' bracing members may be neglected while determining the projected surface of a windward face). of tower frame above waist level which is not shielded by the windward face shall be taken separately for wind calculation of tower.
Gust Response Fa~tor for Tower (GT) and for Insulatol"S" (GI)
Ht. above Values of GT and Gi for terrain categories ground (metre) Upto 2 3
GT = Qust Responses factor depending upon terraln category and height of CG panel above ground level. Values of GT for the three terrain categories are given in Table- .2 r
10
1.70
1.92
2.55
20 30 40
1.85 1.96 2.07
2.20 2.30 2.40
2.82 2.98 3.12
50
2.13
2.48
3.24
60
2.20
2.55
3.34
Solidity Ratio
70
2.26
2.62
3.46
Upto 0.05
80
2.31
2.69
3.58
TABLE .. 3 Drag Coefficient Cdt for Towers
,0.1
0.2 Note: (i) In case of multi-string including V-string no Masking Effect shan be considered. (ii) The total effect of wind on multiple string set shall be taken equal to sum of the wind load on the individual insulator strings. (iii) Intermediate interpolated.
values
may
be
linearly
6.5.3 Wind Load on Towers 6.5.3.1 In order to determine the wind load on tower, the tower is divided into different panels. These panels should normally be taken between connecting points of the legs and br~cings. For square/rectangular lattice tower, the wind load for wind normal to the longitudinal face of tower, on. a panel height of 'h' applied at the centre of
OJ
Drag Coefficient Cd 3.6
3.4 2.9
0.4
2.5 2.2
0.5 and above
2.0
Note: (i) Solidity ratio is equal to the effective area (Projected area of all the individual elements) of a frame normal to the wind direction divided by the area enclosed by the boundary of the frame normal to the wind direction. (ii) Drag Coefficient takes into account the effect of wind load both or. wind ward and leeward faces of the tower. (iii) For intermediate value of solidity ratio, drag coefficient will be interpolated.
Loadings
4
(TM) DURING MAINTENANCE-
6.5.4 Transverse Load from Mechanical Tension of Conductor and Groundwjre due to Wind (Deviation Load)
6.7 TRANSVERSE LOAD CONSTRUCTION AND SAFETY CONDITION,
6.5.4.1 This load acts on the tower as component of Mechanical Tension of Conductor/Groundwire.
6.7.1 Normal Condition-Suspension, Tension and Dead End Towers
Fwd = 2 x T x sin
6.7.1.1 Transverse loads due to wind action on tower structure, conductors, ground wires "and insulators shall be taken as nil.
Fwd T
= Load in Newtons = Maximum t,ension of conductor and Groundwire at every day temperature and 100% of Full Wind Pressure or at minimum temperature and 36% of Full Wind Pressure whichever is more stringent.
4>
= Angle of deviation.
65.5 Total Transverse Load (TR) under Reliability Condition (TR)
=
Fwc + Fwi + Fwt + Fwd
I (6.5.1)
~~.-
.-- .'
6.7 .1.2 Transverse loads due to mechanical tension of conductor or ground wire at everyday temperature and nil wind on account of line deviation shall be considered as follows:TM = 2 x Tl x sin 4>/2 TM = Load in Newtons Tl = Tension in Newton of conductor/groundwire at everyday temperature and nil wind.
_.
(6.5.2)(6.~.~~ .. (~.5.4j
$
= Angle of deviation of the ~~e..
Where "Fwc" and "Fwi" and "Fwd" are to be applied 6.7.2 Brokenwire Condition - Suspension, Tension and on all conductor/Groundwire points. But "Fwt" wind on Dead End Towers tower is to be applied on the tower at ground wire peak and 6.7.2.1 Transverse loads due to wind action on tower cross ann levels. For 400 kV and above, "Fwt" will also " structure, conductors, ground wire insulators shall be taken be" applied at any convenient level between Bottom Cross Arm and ground-level. In case of Normal tower with as nil. extension of any voltage rating one more level at the top of 6.7.2.2 Transverse load due to mechanical tension of extension panel shall be considered conductor o~ ground wire at everyday temperature and nil wind -on account of line deviation shall be considered as 6.6 TRANSVERSE LOADS (TS) - SECURITY follows:CONDITION TM =Tl x sin $12 6.6.1 SuspenSion Towers
6.6.1.1 Transverse loads due to wind action on tower structure, conductors, ground wires and insulators shall be taken as nil.
where TM Tl
.,
6.6.1.2 Transverse loads due to line deviation shall be based on component of mechanical tension of conductors and ground wires corresponding to everyday temperature and nil wind condition. For broken wire the component shall be corresponding to 50% of mechanical tension of conductor and 100% of mechanical tension of ground wire at everyday temperature and nil wind. 6.6.2 Tension and Dead End Towers
6.6.2.1 Transverse loads due to wind action on tower structure, conductors, ground wires and insulators shall be computed as per clause~.l. 60% wind span shall be considered for broken wire and 100% for intact wire.
$
c v c
5 o
6
Ii"
0:
6. O. 'I
L\. cr .1
de
=
Load in Newtons = 50% of tension in Newtons of conductor and 100% of tension of grollndwire at everyday temperature and nil wind "" ." for suspension tower and 100% for angle and dead end towers for both conductor and ground wire. = Angle of peviation of the tower.
Cc uU:
6.1
6.8
VERTICAL LOADS (VR) CONDITION
RELIABILITY
6.8.1 Loads due to weight of each conductor and groundwire based on appropriate weight span, weight of Insulator strings and accessories. " 6.8.2 Self weight of structure upto point under
..h -".a 15(
u.l
Loadings
f I
5
calculated corresponding to minimum design weight span plus weight of insulator strings & accessories only shall be taken.
Longitudinal loads. which might be caused on tension towers by adjacent spans of unequal lengths shall be neglected.
6.9
6.11.2 Dead End Towers
VERTICAL LOADS CONDmON
(VS)
-
SECURITY
6.9.1 Loads due to weight of each cond~ctor or groundwire based on appropriate weight span, weight of insulator strings and accessories taking broken wire condition where the load due to weight of broken conductor/groundwire shall be considered as 60% of weight span. (For intact wire the vertical load shall be considered as given in clause No. 6.8) 6.9.2 Self weight of structure upto point under- consideration of tower panel.
6.10
VERTICAL LOADS DURING CONSTRUCTION AND MAINTENANCE (VM) SAFETY CONDITION
6.10.1 Same as Clause 6.9.1 multiplied by overload factor of 2.0 6.10.2 Same as Clause 6.9.2 6.10.3 Load of 1500N shall be considered acting at each cross-arm tip as a provision of w~ight of line man with tools. f I
6.10.4 Load of 3500N at cross arm tip to be considered for cross-arm design upto 220 kV and 5000 N for 400 kV and higher voltages. 6.10.5 The cross arms of tension towers shalf also be designed for the following construction loads: Tension Tower
Vertical
Lifting point distance
with
Load, N
min. from the tip of cross-arm (mm)
;>
Twin bundle
10,000
600
Conductor Multibundle conductor
2u,000
1,000
6.10.6 All bracings and redundant members of the, tower which are horizontal or inclined upto 15 deg. from horizontal shall be designed to withstand an ultimate vertical load of 1500N considered as acting at centre, independent of all other loads.
.
6.11 LONGITUDINAL LOADS (LR) - RELIABILITY CONDITION 6.11.1 Suspension and Tension Towers ,,,.j jr.·
6.11.1.1
Longitudinal loads for Suspension and Tension be taken as nil.
tower~ ~hal1
6.11.2.1 Longitudinal loads for Dead End Towers shall be considered corresponding to mechanical tension of conduc~ors and groundwires for loading criteria defin.ed in Clause 6.4. 6.12
LONGITUDINAL LOADS (LS) - SECURITY CONDITION
6.12.1 Suspension Towers The longitudinal load corresponding to 50 per cent of· the mechanical tension of conductor and 100% of mechanical tension of ground wire shall be considered under everyday temperature and No wind pressure for broken wire only. 6.12.2 Tension Towers 6.12.2.1 Horizontal loads in longitudinal direction due to mechanical tensi"n of conductors and groundwire shall be taken for loading criteria specified in Clause 6.4 for broken wire(s). For intact wires these loads shall be considered as nil. 6.12.3 Dead End Towers Horizontal loads in longitudinal direction due to mechanical tension of conductors and groundwire shall be taken for loading criteria specified in Clause 6.4 for intact wires, however for broken wires these shall be taken as nil. 6.13
LONGITUDINAL LOADS DURING CONSTRUCTION AND MAINTENANCE (LM) SAFETY CONDITION
6.13.1 Normal Condition Towers
Sm'pensi.on and Tell$ion
These loads shall be taken as nil.
6.13.2 Normal Condition - Dead End Towers 6.13.2.1 These loads for Dead End Towers shall considered as corresponding to mechanical te.nsion conductor/groundwire at every day temperature and wind. Longitudinal loads due to unequal spans may neglected .
be of nil be
6.13.3 Broken Wire Condition 6.13.3.1 Longitudinal loads during construction simulating brokenwire condition will be based on Stringing of One Earthwire or One Complete Phase of sub-conductors at one time.
6
Loadings
6.13.3.2 Broken Wire Condition fo~ Suspension Tower Longitudinal loads during Stringing on Suspension Tower should be nominally imposed only by the passing restriction imposed during pushing of the running block through the Sheave. It will apply only on one complete phase of Sub-conductors or One Earthwire. It will be taken as 10,000 N on one Sub-conductor or 5,000 N on one Earthwire.
6.13.3.3 Broken Wire Condition for Tension and Dead End Towers Angle Towers used as dead en,d during stringing simulating broken wire condition shflll be capable of resisting longitudinal loads resulting from load ·equal to twice the sagging tension (sagging tension is 50 per cent of the tension at every day temperature and no wind) for one earthwire or one complete phase of sub- conductors which is in the process of Stringing. At other earthwire or conductor attachrllent points for which stringing has been completed, loads equal to 1.5 times tbe sagging tension will be considered. However, the structure will be strengthened 'by installing temporary guys to neutralise the unbalanced longitudinal tension. These guys shall be anchored as far away as possible to minimise vertical load. 6.14
I
LOADING COMBINATIONS UNDER RELIABILITY, SECURITY AND SAFETY CONDITIQNS
2. Vertical Load as per Clause 6.10 3. Longitudinal Load as per Clause 6.13.3 and 6.13.4 6.15 ANTI·CASCADING CHECKS All angle towers shall be checked for the following anti-cascading conditions with all conductors arid OW intact only on one side of the tower. 6.15.1 Transverse Loads These load shall be taken under no wind condition. 6.15.2 Vertical Loads These loads shall be the weight of conductorl groundwire intact only on one side of tower, weight of insulator strings and accessories. 6.15.3 Longitudinal Loads 6.15.3.1 These loads shall be the pull of conductorl ground wire at everyday temperature and no wind applied simultaneously at all points on one side with zero degree line deviation. 6.16 BROKEN WIRE CONDITION 6.16.1 Single Circuit Tower Anyone phase or ground wire broken, whichever is more stringent for a particular member. 6.16.2 Double, Triple and Quadruple Circuit Towers
6.14.1 Reliability Condition (Normal Condition)
6.16.2.1 Suspension Towers
6.14.1.1 Transverse Loads as per Clause 6.5
Anyone phase or groundwire broken whichever is more stringent for a particular member.
,
1 6.14.1.2 Vertical Loads as per Clause 6.8
t 6.14.1.3 Longitudinal Loads as per Clause 6.11. 16.14.2 Security Condition (Broken Wire Condition)
16.14.2.1
Transverse Loads as per Clause 6.6
\
,I
i\ 6.14.2.2 Vertical Loads as per Clause 6.9 !
6.14.2.3 Longitudinal Loads as per Clause 6.12. 6.14.3 Safety Condition (Construction and Maintenance) : 6.14.3.1 Normal Conditions 1. Transverse Loads as per Clause 6.7.1 2. Vertical Loads as per Clause 6.10. 3. Longitudinal Loads as per Clause 6.13.1 and 6.13.2 ~; 6.14.3.2 Brokenwire Condition
6.16.2.2 Small and Medium Angle Towers
Any two phases broken on the same side and same span or anyone phase and one ground wire broken on the same side and.same span whichever combination is more stringent for a particular member. 6.16.3 Large Angle/Dead End Towers Any three phases broken on the same side and same span or any two phases and one ground wire broken on the same side and same span whichever combination is more stringent for a particular member. 6.17 BROKEN LIMB CONDITION INSULATOR STRING
FOR
'V'
6.17.1 For 'V' Insulator strings, in normal condition one limb broken case shall be considered. In such a case the! transverse and vertical loads shall be transferred to outer limb
Transmission Line Manual Chapter 7
Design of Tower Members
\
,
CONTENTS Page 1
7.1
GENERAL 7.1.1 Technical Parameters 7.2 STRESS-ANAL"'(SIS 7.2.1 List of Assumptions 7.2.2 Graphical Diagram method 2 7.2:3 Analytical Method 2 7.2.4 Computer-Aided Analysis. 2 7.2.4.1 Plane - Truss method or, 2-Dimensional analysis ') 7.2.4.2 Space - Truss method or, 3-Dimensional analysis 2 7.2.5 Comparison of various methods of stren analysis 3 7.2.6 Combination of Forces to determine maximum stress in each member 3 (i.e., Leg-Member, Bracing-Transverse and Longitudinal, X-arm and G.W. Peak) . 7.3 MEMBER SELECTION 4 7.4 SELECTION OF MATERIAL 4 7.4.1 Use of hot rolled angle steel sections 4 7.4.2 Minimum flange width 4 7.4.3 Minimum thickness of members 4 7.4.4 Grades of steel 4 7.5 SLENDERNESS RATIO LIMITATIONS (LlR) 4 7.6 COMPUTATION OF LIR FOR DIFFERENT BRACING SYSTEMS 4 7.7 PERMISSIBLE STRESSES IN TOWER MEMBERS 5 7.7.1 Curve-l to curve-6 5 7.7.2 Reduction due to bIt Ratio 5 7.8 SELECTION OF MEMBER 5 7.8.1 Selection of Members in Compression 5 7.8.2 Selection of Members in Tension 5 7.8.3 Redundant Members 6 7.9 Bolts and Nuts. 6 Annexures I II III IV V VI
W VIII IX X XI XII XIII XIV
Conductor Details Earthwire Design Loads Graphical Diagram Method Analytical Method Computer Aided Analysis ~mb3DAn~~
Output Giving Summary of Critical Stresses Chemical Composition and Mechanical Properties of Mild Steel Chemical Composition and Mechanical Properties of High Tensile Steel Section List Equal Section Commonly Used For Towers & As Per IS:808 (Part - V) 1989 Llr Consideration for Bracing System in a Transmission Tower . Permissible Axial Stress in Compression Reference Table for Maximum Permissible Length of Redundant Members
7 8 9 II 13 21 M 28 32 33 34 36 37 43
CHAPTER 7 DESIGN OF TOWER MEMBERS
7.1 GENERAL 7.1.1 Technical Parameters Design data for transmission line Towers are discussed in chapters 2 to 6.
7.2. SlRESS ANALYSIS The exact stress analysis of transmission tower requires calculation of the total forces in each member of the tower under action of combination of loads externally applied, plus the dead weight of structlle. The design of structure must be practical so that it is done as a production assignment. Basically the stress analysis of any tower requires application of the laws of statics. As. tower is a space frame the solution becomes complex. if all extemalloads are applied ~imultaneously. Different categories of loads are taken separately for calculation of stress in each member. stresses so calculated. for different types of loads are superimposed to arrive at overall stress in the member.
7.2.1 List of Assumptions (a) All members of a bolted type tower frame work are pin-connected in such a manner that the members carry oxialloads only. (b) The bolt slippages throughout the structures are such as to allow the use of the same modulus of elasticity for the entire structure. thus permitting the use of the principle of super-imposition for stress analysis. (c) Shear is distributed equally between the two members of a double web system. i.e .. warren system. (d) Shear is carried by the diagonal member under tension in a Pratt system with members designed for tension only. the other member being Inactive. (e) Torsional shears applied at crossarm level for square tower are resisted by all the four tower faces equally. (f) Plan members at levels other than those at which external loads are applied or where the leg slope changes. are designated as redundant members. (g) Any face of the tower subjected to external loads lies in the same plane. so far as the analysis . of the particular face is concerned. except earth wire cross-arm and peak. (h) Transverse loads are shared by the members on the transverse faces of the tower equally. Similarly. the longitudinal loads are shared equally by the two longitudinal faces. (i) Vertical loads placed symmetrically and dead weight of the structure are shared equally by the four legs. Vertical load at cross-arm panel will be shared by web member. in some cases.
m
1
(I<)
The tooionaJ loads ae resisted by all the fcufoces In Inverse proportlon of the width of each face.
(I)
All members, placed Horizontally or at an angle, less than 150 to the horizontal. will be checked independently for specified point load, causing bending stresses.
7.2.2 Graphical Diagram Method Stress-Analysis by graphical method I.e.. stress diagram method is the easiest method of stress Analysis but the accuracy of the cdcutated stress by graphical method depends upon the accuracy of stress diagram drawn and measlXement of stresses mode on proportionate Scale. Even the line thickness makes some difference in stress value. Further, for each load on each face, separate stress diagram is required. Some times, due to spJce limitation in a drawing sheet. each stress diagram bears different Scale and overall computation of the stresses become difficult. There is likelihood of some human errO( '. creeping in! whUe computng the stresses. Thus, the graphical method of drawing stress diagram has now become obsolete. However, a typical stress diagram for a Tower is shown at .A.nQexure 4 (2 Sheets).
7.2.3 Analytk::aI Method Basically, all the assumptions which ore mode In stress analysis of Tower by Graphical Method, are also mode while using Analytical Method. However, the colculoti.on of stress in leg-members with staggered bracings on transverse and longitudinal faces are Slightly more intricate. Annexure 5 (8 Sheets) shows the formats for calculating stresses by Anal'jaical Method, for the following tower members:-
leg Member Bracings-Transverse and longitudinal faces. Cross-Arm: Various Members
7.2A Computer Aided Analysis In the previously described methods of stress analysis. viz Graphical Method as well as Analytical Method, a designer has limitations to try-out several permutations and combinations of Tower Geometry. To avoid mental fatigue due to numerous trials. one is inclined to restrict Jo few trials, based on one's experience, thus analytical designs were more or less personified ones. WIth the a.dvent of Digital Computer, now available as an aid to a Designer, hiscapabilrrv is enhanced to try out number of iterations with several permutations and combinations. so as to achieve the optimum design and accurate stress analysis. Two different methods of stress analysis with the aid of computers are being practised.
1.2.4.1 Plane TrusslMlhod Or 2-dimensiond AnalysIs This is exact replica of analytical method, covering all the steps as before but with unlimited scope of trials for variations in tower geometry of bracing systems. Various organisations have developed several computer programmes suitable to use with particular computer system available with them. Some computer programmes are so elaborate that even optimum Tower Geometry is selected automatically by a Computer. But most practical one is that Computer Software working on Interactive mode. It amalgamates the experience of a designer to try a particular geometry along with capability of a computer to try numerous permutations and combinations. The main objective of such an elaborate aid from a computer is to achieve optimum design of a tower, which will withstand slmultaneous application of worst loadings and achieve reliability as well as optimum strength of all tower members.
} .~
The tower structure Is basically a statically Indeterminate structure, 3-o;menslonal Analysis is not possible to do manually, Stiffness matrix analysis with the help of appropriate powerful computer is essential.
STEPS INVOLVED IN 3·0 ANALYSIS OF TOWER a) b) c) d)
A line diagram showing the four faces of a tower Is prepared (Ref, Annexu're,6 ) ( 3 Sheets), Each NODE is numbered sequentially at each level. Every member Joining two nodes Is then numbered, including Plan members at each leve!. Annexure, 7 shows the input data which consist of following:- Coordinates of each Node In a spectfied format. - ConnectMty of members between the Nodes and the sectional areas of the members. - The loads on each Node for all three directions, - These inputs can also be created through computer programmes.
PROCESSING STAGES 1, The first stage gives the 3-D analysis of the tower for each member for each load case. 2. The secord stage uses the out-put of the first stage as input and then gives the st.J'TV1'lOrY of critical stresses for members of each group, (Ref,Annexure 8, 3 sheets), The 2nd stage also requires the Group file as an Input, Wi Sl.J1l'OOry ootput is then ufUized by designers fer final design,
7,2.5 Comparison of Various Methods of Stress-analysis Comparison of stress analysis by graphical. analytical and computer method reveals, that though It does not affect the practical stress design of tower much. the 3-D analysis by computer gives more insight Into stress distribution In various members due to the various extemalloads, Whereas. in the case of graphical and analytical methods it is assumed that the transverse faces take care of transverse loads and memt;>ers of longitudinal faces carry stresses due to longitudinal loads only.the 3-~ stress analysis 'by computer shows the stress distribution in the members of all the four faces of the tower due to any type of external load applied to the structure. Similarty, while doing analysis by graphical and analytical method, stresses are only calculated in the members at the level of the externally applied load and below it, the 3-D analysis gives the magnitudes of stresses even in the members above the level of the externally applied load. Again in the Cross-arm analysis we assume that the main members carry the transverse and longitudinal loads and a portion of vertical load. and the top Inclined members carry the vertical loads, but the 3-D analysis Indicates the top members shore even the transverse and longitudinal loads. 3-D analysis. therefore. give more realistic picture of stress distribution in the Tower and can be used as an effective tool to arrive at the optimum design of Tower In minimum possible time
7.2.6 Combination d Forces, to cktJennlne Maximum Stress In eoch Member Ref.Annexure 6 which gives (] typical Tower Design Calculation. (based on IS:-802(Part 1)-1995 showing combination of forces for (1) Design of Leg members "c", (2) Design of X-arm members. and (3) Design of bracings on Transverse and longitudinal faces,
7.3 MEMBER SElEC110N ~ per IS:B02(Part I) (1995). the concept of limit load theory has to be followed and the tower loadings. covered in Chapter 6 are based on this concept.
3
7.4 SELECnON OF MATERIAL 7.4.1 Use of hot-lolled angle steel sections Since Towers are manufactured in factory'environment and have to be assembled at site. the ease d tr~PQrt and assembly dUrlng tower erection are equally important points for consideration, So far. the practice is overwhelmingly in favour of the use of Hot Rolled Angle steel Sections in the design of Towers, 7.4.2 Minimum Flange width Minimum flange widths for bolts of different diameters are given below:BOLTDIA 12mm 16mm 20mm 24mm
FLANGE WIDTH 40mm 45mm 50mm 60mm
7.4.3 Minimum Thickness 01 Members As per 15:802 the following minimum thicknesses for members are specified: a) leg members b) Ground wire peak and Extemal members of Hom peak c) lower members of cross-Arm d) Upper members of cross-Arm e) Bracings & Inner members of Hom peak 1) Other members
: : : : : :
5mm 5mm 5mm 4mm 4mm 4mm
7.4,4 Grades 01 steel Generally two grades of steel i.e,. mild steel and higher tensile steel are used in the manufacture of transmission line towers. The salient properties of these grades of steel are tabulated in Annexure 11. Annexure 12 and Annexure 13 ( 2 sheets), Properties of angle sections which are normally used in Towers. are fumished.
7.5 SLENDERNESS RATIO UMITAnONS (Kl/R) As per 15: 802 (Part I). section-2. the following limits of L/R ratio are prescribed:-
-leg members. G.W. Peak. and X-arm lower member -~~
- Redundants/Nominal stress carrying members - Tension members
=120 =~
=250 = 400
7.6 COMPUTAnON OF L/R FOR DIFFERENT BRACING SYSTEMS
For achieving desired strength of tower members and optimum weight of full Tower. a Designer adopts several Geometrical patterns for bracings. with and without the use of secondary members, KL/R for bracing patterns are exhibited in Annexure. 12 (2 sheets) (based on 15-802 Part-I Section-2: 1992)
7.7.1 Curve 1 to Curve 6 Various strut formulae for working out the permissible compressive stresses are as per IS: 802(Port l/sec-2): 1992. This code suggests for use 6 different curves for calculation of the permissible' compressive stresses in different tower members. Refer Annexure 13.( 5 sheets) . Curve-1. is used for Leg-members. vertical G.W. Peak members and double-angle sections. connected back-to-back. having concentric loads at both ends and KL/R upto 120. Curve-2. is used for X-arm lower members. having concentric loads at one end. eccentric load at the other ends and KL/R upto 120. Curve-3. is used for bracings with single angle sections having eccentricity at both ends and KL/R upto 120. Curve-~t is used for bracings wtth single-bolt connections at both the ends, thus b.eing unrestrained against rotation at both the ends and having KL/R from 120 to 200. Curve-5. is u~edfor bracing; with sirQe-bolt connectioos at one end 000 2-bo1t comections at the other erd ttus being partblly restrained agdnst rotation at one erd only crd having Kl./R from 120 to 225. Curve-¢. is used for bracings with 2-bo/t connections at both the ends. thus being partially restrained against rotation at both the ends and having KL/R. from 120 to 250.
7.7.2 Reduction due to bIt rotfo Suttoble reduction in permiSSible stresses has to be mode for fimits in bit ratio. as per 15:-802 (part-l)-l995.
7.8 SELECTION OF MEMBERS 7.8.1 Selection of Members in Compression This Design should follow stipulations of Curve-' to Curve-¢, described above (Ref. Annexure 13).
7.8.2 Selection 01 Members In Tension The estimated ultimate tensile stress In a member, should not exceed 2550 kg/crrl the slenderness ratio of member carrying axial tension should not exceed 400. The net effective areas of angle sections in tension to workout the pennlssible tensile load In a member shall be determined as under.(i) Single angle in tension connected on one flange only. A+ BK.where A =Net sectional area of the connected flange B =Area of the outstanding flange =(L-t) t, where L =Flange width. t =Thickness of the member.
1 K=---1 + 0.35 B/A (ii) Pair of angles back to back : connected on one flange of each angle to the same side of g.JSSet. A+BK
5
'N'here. A =Net sectional area of the connected flange B = Area of the outstanding flange. 1
K=---1 + 0.2 B/A The back to back angles are to be connected or stitched together throughout their length In accordance with the requirements of IS: 800·1969 (Code of Practice for use of Structural Steel In General Building Construction). 7.1.3 Redundant- Members Redundant members corry nomnol stress. They are used to restrict the slendemess ratio LJR of the main member$. Slendemess ratio of redundant member is restricted to 250. They ore also required to corry 2.5 % of the stress In the main members. which ore supported by these redundant member. These membe~, It placed at an angle less than 15° ere required to be checked to withstand bending also. due to a mid-point concentrated load of 150 kg Independent of other Ioods (Ref. Annexure 14).
7.9 BOLTS AND NUTS
7.9.1 Tower structures are usuolly BoHed type 7.9.2 The uHimate stresses in bolts shall not exceed the following values: Nature 01 Stress
(a) Shear stress on gross area of bolt.
00sa.4.6
CIaUS.6
2.220
3.161 (310)
(218)
Gross aea of the bolt shdl be taken as the nominal area of the bolt.
(b)
Bealng stress on gross diameter of bolt.
4.4«)
6.322
(436)
(620)
Bott area :neil be taken as dxt wtlefe.
= =
d OIaneter of bolt t Thlckress of the thinner member (e)
Sealng on member
MS HT (d)
Tension
4.4«1
4,440
(436)
(436)
4.4«1
6.322
(436)
(620)
1980
2590
(194)
(254)
7.9.3 The bolt sizes used. are 12. 16.20 and 24 mm diameter PreferabJy not more than two sizes of bolts should be used in one tower. Connection will be designed for the relevant shear and bearing stresses and the closs of bolts used. There will be no restriction on the number of botts.
• • ·)[111I1J1I1.1IJ[I·U Jlro . . r . :..•. ! ... U.IIlunnl·· . 1 r tlJIJm· IIII! JIJ .11.11 HlIIIU ••UIITII11••lillfi II HIII . 111111I1'.IIIOIIIIJU1IL.I.III?DJlJI_
ANNEXURI CONDUCTOR DETAILS Sr. No.
....,
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24.
Strands
Code AI No./mm. Dog _.
7/1.570 7/1.753 26/2.54 7/1.905 30/2.362 7/2.362 30/2.590 7/2.590 Lyon 30/2.794 7/2.794 Lark 30/2.924 7/2.924 Panther - • 30/3·.CXXl 7/3.0CIJ Bear 30/3.353 7/3.353 Goat 30/3.708 7/3.708 Sheep 30/3.980 7/3.980 Kundara 42/3.595 7/1.960 Zebra _. 54/3.180 7/3.180 Deer 7/4.267 30/4.267 Camel- • 54/3.353 7/3.353 Drike 7/3.454 26/4.4424 Mouse - @ 7/3.530 54/3.530 Canary 7/3.280 54/3.280 Dove 7/2.890 26/3.720 Redwlng 19/2.350 30/3.920 Gerslmls 7/2.540 42/4.570 Curlew - @ 7/3.510 54/3.510 Duck 54/2.690 7/2.690 Leg Hom 12/2.690 7/2.690 • Conforming TO IS - 398 (Part 2) - 1976 (UP TO 220 kv) @ Conforming TO IS " 398 (Port 5)1\ - 1982 (400 kv) Leopard Coyote TIger Wolf _.
6/4.72
Steel No./mm.
~/3.283
Ultimate Strength (kg.)
3.305 4.140 4.655 5.800 6.867 7.965 9.080 9.144., 11.330 13.800 15.900 9.054 13.289 18.200 14.760 14.175 16A38
14.650 10.180 15.690 15.734 16.850 10.210 5.360
Overall dia (cm)
1.415 1.585 1.590 1.650 .1.813 1.958 2.047 2.100 2.350 2.600 2.793 2.688 2.862 2.984 3.020 2.814 3.177 2.951 2.355 2.746 3.510 3.162 2.418 1.346
Total Sectional Area (cm2 )
Unit Wt.
1.185 1.485 1.515 1.622 1.949 2.265 2.470 2.615 3.262 4.
0.3940 0.4935 0.5215 0.6060 0.7260 0.8455 0.9230 0.9740 1.2195 1.4915 1.7260 1.2180 1.6210 1.9800 1.8100 1.6280 2.0040 1.7210 1.1370 1.6460 2.1850 1.9760 1.1580 0.5000
Kg/m.
Co-efficlenft ot linear expansion -u· /oc
Modulus of Elasticity Kg/cm'
19.80 x 10-6 19.80 x 10-6 18.99 x 10-6 17.80)( 10-6 17.80 x 10-6 17.80 x 10-6 17.80 x 10-6 17.80 x 10-6 17.80 x 10-6 17.80 x 10-6 17.80 x 10-6 21.50 x 10-6 19.30 x 10-6 17.80 x 10-6 19.30 x 10-6 18.99 x 10-6 19.30 x 10-6 19.30 x 10-6 18.99 x 10-6 17.50 x 10-6 21.50 x 10-6 19.30 x 10-6 19.30 x 10-6 15.30 x 10-6
0.775 x lot' 0.775 x 1(t 0.773 x 1(t 0.816 x 1cf' 0.816 x lcf' 0.816 x 10" 0.816 x 1cf 0.8)6 x let 0.816 x lcf' 0.816 x let 0.816 x lcf' 0.755 x 1cf' 0.704 x let 0.816)( lCf 0.704 x 1(f 0.773 x let 0.704 X 106 0.704 x lct 0.773 x let 0.738 x let 0.755 x let 0.704 x 1(f 0.704 x let 1.050)( let
~·"--C-.7
-:..
,
~',
_
,:~Ji
L-nb~n.~_--
ANNEXURE - 2 EARTHWIRE Sr.
Stranding No./dla.
Weight per metre
Overall DIameter
(mm)
(kg)
(mm)
Total Sectlonal Area (nvn2)
1.
7/3.15
0.429
9.45
54.552
2.
7/3.&J
0.523
10.&J
3.
7/3.66
0.583
4.
7/4.00
5.
No.
Ultimate tensile strength (kg)
700
1100 N/mm'
1570 N/mm'
3699
5913
8297
67.348
4567
7177
10243
10.98
73.646
4994
7848
11201
0.690
12.00
87.965
5965
9374
13379
19/3.15
1.163
15.75
148.069
10041
15778
6.
19/3.&J
1.~
\7.50
\82.801
12396
19479
7.
19/3.66
1.570
18.30
199.897
13555
8.
19/4.00
1.875
20.00
238.761
16191
9.
1/5+8/3.2
0.458
11.40
71.41
&m
N/rrvn'
OPTICAL
FIBRE GLASS Strands
Modulus of Elastlctty - E·
Co-efflclent of linear expansion
-n- perrf c 1.969xlct kg/em'
l1.5OxlO~
7
1.933xHt
11.5Oxl0~
19
1.893xlcf
11.5Oxl0~
OPTICAL FIBRE
1.52x1cf
13.4Ox1O~
: " Jt211Ldll tIm.! lUi db t tEl Lit
UI L ,LIt l'IUJt_niHIl
LIHJtJldllLflI ' • ,
IF I! 1 ',.
I
AiI.I. I "
It.
lbn
LUd •
•
•
Sheet No. 1of 2
DESIGN LOADS ( FOR SUSPENSION TOWER) (REUABllITY CONDmON (NORMAL CONOmON) (32°C & Full Wind)
:;
~,I ....
t •
. 70'.
..I,
i (,r..,
!--_._.
..-
I ;
i7'56
--I
l~'
"'1·" .
N fl' I'fiII .-.
,i
i.---. '!!IIO
,,~~
...
~
17~~
-----~
i
- ......
I
k
," I 175G
..-~
o. V;" Nil:' ~~
"SSM.;l SE,.CURIT) (,\,)NOIilON
orc
(B.W, CONDITION)
& NO MND)
~I~
-.-~
",
'·' '0
_~I~ ,
. ..'0;'
~,~
---_.- ..-......... _._ .. _---
'07
-102 .........
'l'
I
r,'" .... ~'" .~,
._ _.- -...
102
--
LEVEL A
I.\S_s..~..J
~.s.$M~.L~l!,)/ 3A/4~8~
I.!;. I,IL~Q!~.(!I)
(C.QriQ._.BBQ~;E..NJ
NOTES:1. 2. 3. 4. S.
AlL LOADS ARE IN KGS AND ARE ULTIMATE BRACKETED FIGURES INDICATE MIN. VERT. LOADS/UP UFT LOADS. WIND lOADS ON TOWER BODY SHAll BE CONSIDERED IN ASSUMPTION-! ONLY SELF WEIGHT (s.w.) OF TOWER BODV TO BE CONSIDERED EXTRA. SUFFIX 'A' IN ASSM NOS INDICATE RIGHT SIDE BROKEN CON·DITION.
9
ANNEXURE·3 Sheet No.2 01 2
DESIGN LOADS SAFETY CONDITION (NORMAL CONDlnON) (32°C 6 No Wind)
:r.1 w)
1
--
Jl2 ....10;: -~
.. -_ ..
---
~l
~1
"
-102 ......
~
...~I
---102
- - -102-
----
~I
--102
-
102
~1
LEVU
A
~I
ASSM:6
SAFEIY CONDITION
- 21"~ ~
,-;-----~ .... " ",. °1' 10~
IIl2
,
~ --_ ... _-+-~ "j
-
'°1
102
~I
(8 W. CONDITION)
(~2.Ie. (~ tw
'''1))
~, .-~-.---
gl -
102
~~t
.,-
102 - " - - - ' - ; - - --- --...
•1
rJ
-.-
l[\~', A
(G.J.V, STRINGIN~)
.... °1••
102
102
~I
AS.s.~:7
---
lE'/EL "
A~SM:8/9/1 QiJ~[\L~jJ.Q~
CC.Qt1lL.~HlH.G!NG.)
NOTES:I. AlL LOADS ARE IN KGS AND ARE ULTIMATE 2. 3. 4. 5.
Y'f
BRACKETED FIGURES INDICAlE MIN. VERT. LOADS/UP UFT LOADS. WIND LOADS ON TOWER BODV NEED NOT BE 'CONSIDERED SELF WEIGHT (SW.) Of TOWER BOOY TO BE CONSIDERED EXTRA. StJFFIX 'A' IN ASSM NOS INDICATE RIGHT SIDE BROKEN CONDlTluN.
:ifleeT NO. I Of 2
~
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en ",
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en
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Trans. Face
Stress Diagram
11
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:;neef No. I Of 8
ANALYTICAL METHOD
.
~
N
~ UI
on
BOlTQU Pl}.N ~
"l
0
~
8~ 01
~
~
-
0 0
~
PART-l ~
-
r-.
.,.g~ ... ~
8 .....
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PART-2
8 ('I
TRANSVERSf:. FACE
.tiQIE .. 1. ALL DIMENSIONS p.p.E IN
mm.
13
or
BOTIOM X-ABU
ANNEXURE· 5 Sheet No. 2 of 8
DESIGN OF T
ASSM-1 (te)
(240 + 705) '1C
=
x 14.566
(650+-2x1756) x 8.936 (880 + 2 x l756)x 4.036 M
STRESS
=
=
M
2 x Wx Cos ~
Vertical load = Max = 219
=
13765
=
=
37192 17726
=
68683
. l
68G83 2 x 2.114 x 0.999
= 16261
=
+ 6 x 929
1448
4
Vertical load = Min
= (73
= (553)
+ 6 x 356)
4
Self weight of
D5
x 75 x 6
1 Imin
Tower
(1
= 1600/4
::
~OO
carpressioo
= 18109
Tensioo
= 15308
= 864/0.999 = 865)
= 86.5 = 59.25
U1t. compressive strength = 2265 x 8.66 = 19615 (Q1 Gross Area) Safety margin over limit load (s-t) -S.M. =1.098
1.46
Ultimate Tensile strength = 2549 x 6.56 ~
= 16721
S.M.
= 1.09
(On Net Area) ~
12 mn dia. Bolt - 6 Nos. (Single Shear) Ultimate Shearing strength = 21450 Ultimate Bearing strength
=
S.M. = 1.06
19181
12 om dia. Bolts 6 t<>. (Double Shear) Ultimate shearing strength = 42900 a:...-....-._
....
,
__ ~._
l_
v__
__~
.... "
1,...,,ft,,..
!!t.~
~"
Mo... ~a
(
Sheet No.3 of 8
DESIGN OF £RACINGS
'SfO -, • 0 C"'1 \.0
In
c.. .'t-I.
~ Fb FUR TRANS. FACE
ASSM-l
I
I
I
,
1750
= =
Me = (SSO+2x1756)x 1.950
=
1436 7284 8564
=
17284
TC
T.e..
(OC)
= (240 + 705) x·I.520 = (650+2x1756)x 1.750
GW
,I
9R""'NG.r
0
LFb
(j
(7\
i
Fb FOR
1'6,
I..(N;.
FACE BRAC.'N~S
M.e· ~SM
0
-
4
(~
BROKm)
x 1.950 = 2857 Tbrsion (Me)= 1465 x 4.20, = 6153
Me = 1465
0
(j\
't
I
~3
e.c.. .
215(p
Pl-- J '
ZFb
=
9010
DESIGN OF TRANS. FACE t3 RRC./tJt'. S '~'
1
l.oBo
o
o t-
4x
- /\g;-4a 2. .1.1li ) (
./
·"".,l
.. {~_
= 1.379
'.
Wx
Cos:.>\= 4 x 2.114 x 1.075 = 6.59 1.379
STRESS =
~4
~ Fb = 17284 = 2623 (Canpression ----4.W.Cos~ 6.59 .
2.lSb
L 45 x 45 x 4
1 min
=
137.9 0.87
=
158.51
= 3126
S.M.
= 1.19
Ultimate tensile stsrength = 2549 x 2.2lS = 5654
S.M.
=
Ultimate compressive strength
= 901
x 3.47
12 mm dia. Bolt 2 Nos. (Single Shear) Ultimate Shearing strength = 7146 U1 timate Bearing strength = 4888
S.M.
15
= 1.86
2.15
&
Tension)
ANNEXURi·5 Sheet No.4 of 8
DESIGN OF L9NG. FACE BRACING .~'
1 S'mESS
= 1.379
4.W.Cos,( = 6.59
= -4.W. -006
= ~ Fb
9010 = 1368 6.59
L 45 x 45 x "
1 min
=
137.9 0.87
= 158.51
Ultimate Cmpressive strength = 901 x 3.47 = 3126 Ultimate Tensile strength = 2549 x 2.218 = 5664 12 mn dia. Bolts 2 Nos. (Single Shear) Ultimate Shearing Strength = 7150 Ultimate Bearing Strength = 4262
S.M.
=
3.11
S.M.
= 2.28
S.M.
= 4.14
.......
~..,~
-
..
Sheet NO.5 of 8 .
DESIGN OF BOTTOM X-ARM
Design of tower Merrber.
Length =
J1.0752 + 3.1252
:
3.30
S'1RESS IN' MEMBER
ASSM-10 (OC Broken) :
=
ST "
51 x 3.30
2 x 3.125
=
sv = 1857 x 3.30 =
+ 27 + 3546
2 x 0.864
SL
=
1000 x 3.30
2.150
=
+ 1534
5107
Cbmpression
Tensioo
=
L60 x 60 x 5 (3300/2 1 nned
= 1650)
= 165 = 90.65 1.82
= 1793 x 5.75 = 10309 Ultimate Tensile Strength = 2549 x 4.00 = 10196
Ultimate Compressive Strength
12 mm dia. Bolts 3 Nos. (Single sheat) Ultimate Shearing Strength = 10719 Ultimate Bearing Strength = 9165
S.M.
17
= 1. 79
S.M.
= 2.01
S.M.
=-
ANNEXURE·5 Sheet No.6 of 8
DESIGN OF UPPER MEMBER.
1E'ngth
=J 0.8642 + 1.057~-3.1432
srnE.c)S IN MEM3ER
sv = 2520
=3.426
(ASSM-6)
x 3.426
2 x 0.864
= 4996
(Tension)
L 45 x 45 x 4
=
1 - nned
342.6
1.37
=
250
Ultimate Tensile strength
= 2549
x 2.218
= 5654
S.M.
S.M.
= 1.46
12 nm ella. Bolts 3 Nos. (Single shear)
i I
i
Ultimate Shearing strength
=
10719
Ultimate Bearing strength
=
7332
·1
! DESIGN OF TRANS. BELT. ~
ST
=
IN MEMBER (ASSM-IO OC Broken)
102 - 51
=
4
-+
13
=
+ 3958
SL = 1000 x 3.125 2 x 2.150
=
+ 727
Catpression
=
4698
Tension
=
sv
=
(1857 + 2520) x 3.125 4 x 0.864
= 1.13
ANNUUIlt· :;
SheetNo.7of8
~E
BELT
(CCNI'INUEl»
L 65 x 65 x 6
=
1
rmin
215 = 170.6
1.26
= 691 x 7.44 = 5141 strength = 2549 x 5.317 = 13553
Ultimate COmpressive strength
F.0.5.
= 1.09
Ultimate Tensile
F.O.S.
=-
= 1.52
12 mm dia. bolts 2 Nos. (Single shear)
Ultimate Shearing strength
=
7146
Ultimate Bearing strength
=
7332
F.0.5.
=2549 x 2.218 =5654
S.M.
= 3.56
S.M.
= 2.68
pesign of
UN; ~
BELT.
s:nm;S IN MEMBER
=
ST
102 x 2.150 4 x 3.125
sv = 2520 x 2.150 4 x 0.864
SL
=
(MSM-6)
=
+
18
= -1568 =
CcJTpressioo
=
Tension
=
1586
L 45 x 45 x 4
1,
nru.n
=
215
0.87
= '47
Ultimate Tensile Strength
12 mn dia. Bolts 2 Nos. (Single shear)
Ultimate Shearing strength
=
Ul timate Bearing strength
= 4262
7150
ANNEXURe - S Sheet NO.8 of 8
DESIGN OF PIJ\N BRPCIN:;
fi
.1~·~2
lslgth of Bracing
=
S'mESS IN MEMBElt
(ASS+-S - B.C. Broken)
SL = (1465 x 4.2 4 x 2.150
z:
.1502 + 2
I
= 3.040
~) f2 - 494 (Carpressioo ."•
I Tensioo)
L 45 x 45 x 4 1
=
152
tminO.87
= 174.7
Ultimate Compressive strength Ultimate Tensile strength 12
RIO
ma.
= 660
x 3.47
= 2549 x 2.218
= 2290
S.M.
-= 4.63
= 5644
S.M.
= 11.44
S.M.
= ".31
Bolt 1 No. (Single shear)
Ultimate Shearing strength = 3573 Ultimate Bearing strength
=
2131
bill I .1111 . L
JUiLJUllllUn
H
a
I. JJL._ lI11LIUJrn If1l1l,11 lp·rntrf 111111_UII ill! IJl]IIIIl 1.IIIH.TCllUllJI_ _
! lne
COMPUTER AIDED ANALV'SIS cAogtam IhowIng Few Foe.t of Tow., with HOC» Humbert.
• ''''''''''-
'>f(1)t'
~
w-::
~*
Ie' I
J,f'"
Lk""':
::::""""16
u,.....:::::
~·Z
~
==-68
"f( I ~
~
--...... 'I
-=:::...,. • z
I )111'1
,{' I
)fA
,
~e.1I
Y.E'I'
""~
.
PL':'N
.....
N
t
TRANSVERSE rACE A
-9.·.... - ...·, .. 5'"-"'*,
I
,.,."
I""""
LONGITUDINAL rACE B
r='!('::';"...·'~e'-r6'y.:..":7"-"::...~ .. "-.i.':'_"::~~'!'"r;;.! ........ ...u.---=.!'."· ....·-,;."'l>'~~::~~~7;
..
'z_
::
I
'-lIt1
TRANSVERSE rACE C
V97
~9
LONGITUDINAL .F"~CE B
§ ¥::
~'-:-&::-'::~~..:.~:~.~:;:-;..,l.~"-'~'
MEMBER NUMBERS tOR 3D ANALYSIS
KEY PLAN
~ z
~
';;)~
(:;;. ~
TRANSVERSE tACt A·
LONGITUDINAL tACE B
...------....---.....-----------------....
---~-~--.•. --- .. --
TRANSVERSE tACE C
LONGITUDINAL tACE B
0-
.IIIFlll-]' .•Hlllinrrrr;:T]_11I It'] 111 . I IlltlllUllJIfT 'UlItliI . IF Ill" :nllllnnllillUJ 1[111111 111111 IIIIFllllltllllftlUI'flllJIUrlJlnnTIII UI
MEMBER NUMBERS
~
NODE NUMBERS rR 3D-ANALYSIS
~==~. BOTTOM PLAN OF TOP CROSS ARM
I\)
w
.42
BOTTOM PLAN Or MIDDLE CROSS ARM
a
~
i wil
~.
BOTiOM PLAN OF BOTTOM CROSS ARM ISOMETRIC VIE""
-
ANNEXURE· 7
~TAAO TRUSS UNIT MH KG tNPUT WIDTH 7t OUTPUT WIDTH 79 INPUT NODESIGN JOINT COORDINATES • IN GLOBLE AXIS
•
,
NODE
3 5
, 7
"
13 15 11 11
2'
23 25
u
21 31 33
35 37
3'
41 43 4S 47 4' &1
~3
,55
S7 5' 11
13 15 •7
•• 11
X
-5025. -660. 660. -2010. -100. 2010. 100. -5025. -723. 723. -7$5. 15S. -190. 790. -818. 818. O.
818. -848. ,48. -5200. -873. 873. -904. 90~.
-934. 93'. -91515. 9&15.
o. ne.
-1000. 1000. -5150. -1291. 1291.
73 75
-un.
77 l' 11
-2180. 2180. -2770. 2770.
83 as a7 at
"15
•3 •1
9'
101 t03 t05 '07 t09
1697.
-349~.
3(94.
-lIOO. lIOO.
0. 3900. -U12.
""2.
-4558 . -4551. -1412. -3412. -4412.
(If4)
INPUT FOR 3D ANALYSIS
X +VE LEFT TO RIGHT Y
O. -2050. -2050.
-1560.
-2,5~5.
396.
-36S0.
700. J96. 700. O. 723. -723. 755. -755. 790. -790. 818. -Bt8. 8ta.
-25~5.
...3650. -3650. -~SSO. -~5S0.
-5650. -5850. -7250. -7250. -8360. -8360. -8360. -8360. -9550. -9550. -95S0. -10550. -10550. -11S00. -11800. -13000. -13000. -14280 .. -14280. -14280. -14280. -1565~.
-15650., -151550. -17eeo. -17&80. -20510. -20510. -23735. -23735. -279815. -27986. -33030 , -33036 . -358158. -35815&. -358&&.
-35see .
-39438. -3U38. -40431. -40438. -39438 . -19438.
-3'4315.
l ~
e
660.
8 10
,.
12
., 40
U
I
o.
eo
U
88
O.
68
1291. -1291. 1897. -1&97. 2160. -2180. 2770. -2770. 3494. -349. . ; 3900. -3900 . 3900.
70 72 74
7&
7! 80 @2 @(
88 l'8
-.
90
I
o.
4' 50 52 S. 515 58 e2
1000. -1000.
. I
U12.
-"'2. 4551. . I
-4551. 4412. -4412 . ," 3412.
92 U .
-2010. -100. 2010. 700.
-1$5.
~2
.',
no.
24
3.
o.
-880. 5025.
20 " 22 2& 28 JO 32 34 38
8.8. -848.
J(
S025. 723. -723. 755.
11
O.
873. -873. 904. -90 •. 934. -934. 91515. -9U. 9815.
:y +ve UP ;z +ve 00; SIDE NOOF.
Z O.
9&
te 106 102 10.
no.
-790. 118. -ate.
-I,..O.
148. -8U. 5200. 873. -873. 90'. -9(\ •.
'H.
-.3 •. '1515. -91515.
o.
-915&. 1000. -1000. 5150. 129 I . -1291 . 1&97. -1&97. 2160. -2160. 2770.
-2770. 3494. -3.,4. 3900. -3900. O. -3900. U12.
-"'2. '~50.
we
455&. 5412. 5'"' 2.
"0
4,",2.
1~
Y
-205".
o.
-2050. -2~4S.
-3850. -25H. -lI50. - 3150. -4550. -.550. -5850. -5850. -7250. -7250. -8leO. -8380. -83150. -!3&0. -9550. -9550. -95S0. -t0550. -t05S0. -11800. -11800. -13000. -13000. -14280. -142S0. .-142S0. -142BO. -151550. -15850. -15&50. -171580. -17880. -20510. -20510. -23735. -23735. -279!15 • -27980. -33030. -33030. -3581515. -358815. -35815&. -35815e. -39438. -39438. -40438. -40431. -39.38. -39"31. -39"36.
Z 6&0. O.
-no.
-He.
-700.
-In.
-700.
O.
723.
-723. 7S5. -755.
no.
;-190. 818. -118. -818. O.
'.8.
-us.
O. 873. -873 . 904. -904. '34. -934. 951.
-see.
-gee.. O. 1000. -1000 . O.
12" . ':12". 1897.
-1697. 21150. -2180. 2770.
-2770. 349'. -3(94. 3900. -3900.
-uoo.
O.
4412 • -4412.
4551. -455 ••
".12 .
-4412.
3412.
ANNEXURE ·7 (3/4)
INPUT FOR 3D ANALYSIS COtlS rANT S IJtlI T eM E 2047000
ALL
• ~eMOER rRQPERTIES -MEMBER PROPERTI~S • · .... ,.,
Itl[.:lMI
,
~
••
•·
3
...'"
UPT I
9 2
10
UPT 1
11
12
UPT 1
13 *• 4 17
.
2
*•
2
21
25 27
14
15
16
upt
18
19
20
UPT 1
41
• 2
\
22
23
24
UPT
3
,
3 26
UPT 1
28
UPT 1
30
31
32
U~i
., t
..,;
34
u~r
36
37
38
UtlT 1 2
40
Ur:'T 1
42
lJPT 1 2
3
* • 452
~6
UPT 1
48
CPT 1
50
UPT
49
')
,
,.
Ii
PEIIY. . IN( R) A
5 J, reM' Of( L)A A € 1;:( 6~v 5 , (;pr1ur H0, PFAK ~T(L)B II 41))'
,CP(ltJP
45:t
tI()-
~5v
110-
"
6r,v 6
5, PfM N(P)"
65X 65)1 ,GROUP NO- 5, 6SX 55X ,GPc)UP NO- 7 , 65X 651 45'1
.A
6
PEAK_OT(P)B." 6
LEG,"
6
0, IRAN_A
5 ,cnoup NO- g, LONG_A 45X 45X 5 ,GROUP NO- 10, TR_BELT TOP_A .t~x
-
45X 45X 5
45X 45X 5
,GROUP NO- t 3, UM LG._BL T_A 45X 45X 5
i
3
UPT
..
.t~~
1111\ )
,GROUP NOLG_BELT_TOP_A t" 45X 45>: 5 3 . ,GPOUP 1'10- 12, UM':' TR_BLT_A
44
H • 2
I1SO: ,C;HnUP 1-1')-
,. Pfll"
3
43
• 2
~I('-
-,GPOUP NO-
3
4
35 *• 2 39 *• 2 :&
1
4
29 *. 2 JJ
*•
1
4
• <;p'(II}r'
....~n(Jup
1
4
*•
I
8
*.
*•
lIpr
UI-l- ,,
7 .. , *•
·
4
,
6
5 2 *•
.•
urI
~
,
1
3
3 3 1
,GROUP NO- 14, LONG_OX_A 45)( 41\:< 5
,GROUP
~IO-
15, LM_LT TC
-
90l( 90X Ij ,GROUP NO- 16, UM_LT_TC 45X 45X ~\
,GROUP NO90X ,GROUP NO45X ,GROUP tlOe.;f ~ ,GROUP 1:045X
17, LH_RT_TC
90X 6 18,
UM_RT_TC
45X 5 t 9, TR .. BEL T_II. 1 51)X 5 20, LG._BEL T_A 1 5
~5~
,,
(4/4)
. CASEOI --)C-INC Vmx QADHIG 4 C-INC YmJ(
INPUT FOR 3D ANAlYSIS
f1.00+2.00*C' .00.0.00)+( I .OOort .00t
tNT LOADS
477 F';' -332 FZ 477 FY -332 FZ FY -1233 FZ 1C-1NCSC Vmx 'JADING 6 C-1NCSC Vmx ,INT LOADS 1 FX 477 FY -332 FZ • FX o FY o FZ 15 FX 1'.5· FY -123~ FZ ISFX o FY o FZ 41 FX 1445 FY -1233 FZ l2 FX o FY o FZ ~7 FX I·U5 FY -1233 FZ as FX o FY o FZ CASE02 --)C-1NCSC Vmn LOADING 7 C-l NCSC Vmn JOINT LOADS 1 FX 477 FY -to FZ 4 FX o FY o FZ IS FX 1445 FY -83 FZ 15 FX o FY o FZ 41 FX 1445 FY -S3 FZ 42 FX o FY o FZ 57 FX ·1445 FY -83 FZ 58 FX o FY o FZ IFX 4 FX 15 FX
0 0
"'5
I)
"'S
C'
""5
0
0 CI
0 (2.00+2.00-(1.00 4 O.OO)+(1.01)0rl.00) t)
0 0 0 0 0 0 0 (2.00+2.00*(1.00+0.00)+(t.OOorl.00) 0 0 0 0 0
0 0 0 (2.00+2.00*( 1.00+0.00)+( 1.000rl.00) 0 0 0 J
0 0 0 0
PROBLEM STATISTICS PRINT MEMBER PROPERTIES ALL PERFORM ANALYSIS PRINT ANALYSIS RESULTS ALL PLOT DISPLACEMENT FILE FINISH ~RINT
27
".'j
ANNEXURE· • Sheet 10f4
OUTPUT GIVING SUMMARY OF CRITICAL STRESSES
Job
: STAAD TRUSS LOA 0 I N G
CAS E S
Ld = Jt.Loads::Tw = Tr. Wind::Lw
Load NO 1 2 1 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 )9
40 41 42 43 44 45 46 47 48 49 50
Case
SELF WEIGHT LOADING TRANS. WIND LOADING LONG. WIND LOADING C-1NC VHX C-INC VMN C-1NCSC VMX C-INCSC VHN C-1GWL VHX C-1GWL VMN C-1GWL VHX REV C-1GWL VMH REV C-1GWSC VMX C-1GWSC VMN C-1GWSC VMX REV C-IGWSC VMN REV C-ITCL VMX C-ITCL VMN C-1TCL VHX REV C-ITCL VHN REV C-ITCSC VHX C-ITCSC VHN C-ITCSC VMX REV C-ITCSC VMN REV C-IMCL VMX C-IMCL VHN C-IMCL VMX REV C-IMCL VMN REV C-IMCSC VMX C-IMCSC VMN C-IMCSC VMX REV C-IMCSC VMN REV C-IBCL VMX C-IBCL VMN C-IBCL VMX REV C-IBCL VMN REV C-IBCSC VHX C-IBCSC VMN C-IBCSC VHX REV C-1BCSC VMN REV C-2NC VMX C-2NC VMN C-2NCSC VMX C-2NCSC VHN C-2GWL VMX C-2GWL VMN C-2GWL VHX REV C-2GWL VMN REV C-2GWSC VMX C-2GWSC VHN C-2GWSC VHX REV
= Lg.
Description
Wind(-ve means Rev.)::Swt = Self Wt. Factor Of Safety Ld + Ld*( Tw ± Lw ) + swt
Factor Of Safty = 1.00 Factor Of Safty - 1.00 Factor Of Safty = 1.00 2.00+2.00X(1.OO+O.00)+1.OOorl.OO 2.00+2.00x(1.OO+O.00)+1.OOor~.00
2.00+2.00x(1.00+0.00)+1.OOorl.OO 2.00+2.00X(I.00+0.00)+1.00orl.OO 1.25+1.25x(1.OO+O.00)+1.00orl.OO 1.~5+1.25X(1.00+0.00)+1.00orl.00
1.25+1.25x(1.OO+O.OO)+1.OOorl.OO ~.25+1.25x(1.00+0.00)+1.00orl.00
1.25+1.25x(1.00+O.OO)+1.OOorl.OO 1.25+1.25x(1.OO+0.OO)+1.00orl.00 1.25+1.25x(I.00+0.00)+1.00orl.00 1.25+1~25x(1.OO+O.OO)+1.OOor1.00
1.25+1.25x(1.OO+O.OO)+1.OOorl.OO 1.25+1.25x(1.OO+O.OO)+1.OOorl.OO 1.25+1.25x(1.OO+0.00)+1.OOorl.OO 1.25+1.25x(1.00+O.OO)+1.00orl.OO 1.25+1.25x(1.OO+O.OO)+1.OOorl.OO 1.25+1.25x(1.OO+O.OO)+1.OOorl.OO 1.25+1.25x(1.OO+O.OO)+1.OOorl.00 1.25+1.25x(1.OO+O.OO)+1.OOorl.OO 1.25+1.25x(1.OO+O.OO)+1.OOorl.OO 1.25+1.25x(1.OO+O.OO)+1.OOorl.OO 1.25+1.25x(1.OO+0.OO)+1.OOorl.OO 1.2S+1.25x(1.OO+O.OO)+1.OOorl.OO 1.25+1.25x(1.00+O.OO)+1.OOorl.OO 1.25+1.25x(1.OO+O.OO)+1.OOorl.OO 1.25+1.25x(1.OO+O.OO)+1.OOorl.OO 1.25+1.25x(1.OO+O.OO)+1.OOorl.OO 1.25+1.25x(1.OO+O.OO)+1.OOorl.OO 1.25+1.25X(1.00+0.00)+1.OOorl.OO 1.25+1.25~tl.OO+O.OO)+1.OOorl.OO 1.25+1.25x(1.OO~O.OO)+1.OOorl.OO
1.25+1.25x(1.OO+O.QO)+1.OOorl.OO 1.2S+1.2Sx(1.OO+O.OO)+1.00orl.OO 1.2S+1.25x(1.OO+Q.OO)+1.OOorl.00 1.25+1.25x(1.OO+0.OO)+1.OOorl.00 ~.OO+2.00X(O.7011.00)+1.OOorl.oO
2.00+2.00x(O.70+1.00)+1.OOorl.OO 2.00+2.00x(O.70+1.00)+1.OOorl.00 2.00+2.00x(O.70+1.00)+1.OOorl.OO 1.25+1.21x(0.70+1.00)+1.OOorl.OO 1.2~+1.25x(O.70+1.00)+1.OOorl.OO 1.25+1.~5X(O.70-1.00)+1.OOorl.00 1.25+1.~5x(O.70-1.00)+1.OOorl.OO
1.25+1.25x(n.70+1.00)+1.OOorl.OO 1.25+1.~~x(O.70+1.00!~1.00orl.00 1.25+1.~5x!O.70-1.00)+1.OOorl.00
. i
SheeT"l.
Job
or 4
: STMD TRUSS SUMMARY OF 3D_FORCES(ULT)
------------------------------------------------------------------------------GRP COMP. LOD MEM TENS. LOD ME SECTION (AREA) CRC i.0 MEMBER NO
NAME
(As Input)(Sq.cm)
(mm)
(Kg)
NO
NO
(Kg)
NO
M
------------------------------------------------------------------------------5244 1 PEAK_IN{L)_A 45X 45X 5( 4.28) 1 4867 9 1 -4494 10 2 1 4 5 6 7 8 8 9 9 10 11 12 13 14 14 15 16 17 18 19 20 21 21 22 23 ~J
, 24 24 25 26 26 27 27 28 29 29 30 30 31 32 '33 34 '35 36 37 38 "39 40
P!A1CIN (R)_A PEAK_OT(L)A_A PEAX_OT{L)B_A PEA1COT(R)A_A PEA~COT{R)B_A
LEG_A TRM'-A TRAM_A LONG_A LONG_A TR_BELT_TOP_A LG_BELT_TOP_A UM_TR_BLT_A UM_LG_BLT_A LONG_OX_A LONG_OX_A UCLT_TC UM_LT_TC LM_RT_TC UM_RT_TC TR_BELT_Al LG_BELT_Al PLAM_BR_Al PLAH_BR_Al LEG_B TRM'-B TIW'-B LONG_B LONG_B LEG_C TRAN_C TRAleC LONG_C LONG_C LEG_D TRMeD T1WCD LOHG_D LONG_D LEG_T_ET TRAN_T_ET LONG_T_ET LEG_B_EB TRAleB_EB LONG_B_EB TR_BELT_EB LG_BELT_EB LM_LT_MC UM_LT_MC
45X 65X 65X 65X 65X 65X 45X 4,)X 45X 45X 45X 45X 45X J!5X 45X 45X 90X 45X 90X 45X 55X 45X 45X 45X 65X 70X 70X 70X 70X 90X 70X 70X 70X 70X 90X 70X 70X 70X 70X 90X 75X 75X 90X 75X 7:;X 45X 45X 90X 45X
45X 65X 65X 65X 65X 65X 45X 45X 45X 45X 45X 45X 45X 4SX 45X 45X 90X 45X 90X 45X 55X 45X 45X 45X 65X 70X 70X 70X 70X 90X 70X 70X 70X 70X 90X 70X 70X 70X 70X 90X 75X 75" 90X 75X 75X 45X 45X 90X 45X
5( 6( 6( 6( 6( 6( 5( 5( 5( S( 5( S( 5( S( 5( 5( 6{ 5( 6( 5( 5( 5( 5( 5( 6( 5( 5( 5( S( 6( 5( 5( 5( 5( 6( 5( S( S( S( 6( S( 5( 6( 5( 5( S( 5( 6( S(
4.28) 7.44) 7.44) 7.44) 7.44) 7.44) 4.28) 4.28) 4.28) 4.28) 4.28) 4.28) 4.28) 4.28) 4.28) 4.28) 10.47) 4.28) 10.47) 4.28) 5.27) 4.28) 4.28) 4.28) 7.44) 6.77) 6.77) 6.77) 6.77) 10.47) 6.77) 6.77) 6.77) 6.77) 10.47)
1 1 1 1 1 1 3 3 3 3 3 3
3 3 3 3 2 3 2 3 3 3 3 3 1 3 3 3 3
1 3 3 3 3 1 6.71) 3 6.77) 3 6.77) 3 6.77) J
10.47) 7.27) 7.27) 10.47) 7.27,. 7.27) 4.28) 4.28) 10.47) 4.28)
29
1 3 3 1 3 3 3 3
2 3
4867 3965 1741 3965 1741 1601 1019 1081 1019 1081 1320 1320 1462 792 735 1299 4381 3235 4381 3235 1400 1400 990 990 901 828 856 828 856 1301 963 1006 963 Hi06 1401 1019
1066 1019 1066 1111 1363 1363 1191 1462 1462 818 818 4434 46"..4
2443 6762 6381 3482 2998 5324 6259 6259 1431 1431 2849 1523 2990 158 674 674 16791 3005 9105 2080 10568 876 5414 5414 13238 6679 6679 8080 8080 11273 8366 8366 7560 7560 15668 7024 7024 8483 8483 18193 9774 8837 18770 7797 8453 2840 1790 14024 3018
113 8 8 114 114 78 78 78 78 78 113 76 17 5 112 112 18 17 114 113 112 5 18 18 78 17 17 17 17 78 18 18 20 20 16 19 ·19 17 17 18 18 22 18 16 20 25 76 26 27
3 5 7 1'0
12 13 18 18 22 22 25 27 29 33 35 35 40 41 44 45 47 49 52 52 53 57 57 64 64 68 71 71 76 76 78 83 83 88 88 91 95 99 103 106 112 113 117 122 124
-3356 -6882 -6247 -2432 -2035 -3857 -6242 -6242 -1208 -1208 -8644 -64 -7396 -569 -808 -808 -13611 -7269 -6743 -7294 -7683 -2815 -4840 -4840 -9338 -77i4 -7714 -6974 -6974 -8261 -7246 -7246 -8754 -8754 -12946 -8102 -8102 -7326 -7326 -14537 -8467 -10233 -14654 -8020 -9850 -9132 -563 -10105 -9658
114 15 13 113
115 1 '78 1 78 2 78 2 78 2 78 2 76 2 7 2 76 3 76 3 11 3 11 3 19 3 78 4 113 4 76 4 115 4 76 5 19 5 19 5 78 5 16 5 16 5 22 6 22 6 78 6 17 7 17 7 17 7 17 7 9 8 16 8 16 8 20 8 20 8 17 "9 17 9 17 9 17 10 92 10 19 11 76 11 31 11 27 12 78 12
Job
ANNEXURE·6 Sheet 3 of 4
: S7AAD TRUSS
ULTIMATE
FOUNDATION
FORCES_3D~IN
Kg)
ALL MAXIMUM ) SR NO 1 2 3 4
5
COMP •. FORCE
UPLIFT FORCE
53188 -39115 49338 .-42964 27780 -19105 39121 -27957 22259 -145Sf
TRANS. FORCE
LONG. FORCE
1159 1153 1812 1218 P12
LOAD NO
64.
4 5
42 1215 1520 1501
36 68 116
DESCRIPTION MAX MAX MAX MAX MAX
COMPRESSION UPLIFT TRANSVERSE LONGITUDINAL (TR~2
+
LG~2)AO.5
Critical Load Cases
------------------4
5 29 31 118 119
7 33
8 34
9 35
10 36
11 37
13 38
[ TOTAL NO OF CRITICAL CASES
16 68
15 39
=
42
17 70
18 76
19 78
20 21 22· 24 25 26 27 92 112 113 114 115 116 117
,lob
: S1'AAD 'flWSS
ULTIHATE
FOUNDATION FORCES_30(IN Kg)
LOAD NO
COHP. FORCE
UPLlf"r fORCE
TRANS. FORCE
LONG. FORCE
LOAD NO
COHP. FORCE
1
2938 5579 49338 31920 37504 )7504 26618 26618 42267 42267 31381 31J81 40561 40561 29675 29675 38887 38887 28001 28001 47793 34944 35508 35508 27477 27477 39465 :;9465 31435 31435 38063 380(\3 30032 30032 36685 36685 28655 28655 6294 4296 8269 8269 7020 7020 12026
2907 -5579 -42964 -25810 -31131 -31131 -20410 -20410 -35677 -35677 -24956 -24956 -34045 -34045 -2)324 -2)324 -32269 -32269 -21548 -21548 -41419 -28834 -29172 -29172 -21307 -21307 -32952 -32952 -25087 -25087 -31.610 -J1610 -23745 -23745 -30150 -30150 -22284 -22284 60') 2078 -1654 -1654 -735 -7)5 -5259
27 2 1153 1179 1098 1098 1114 1114 1518 1518 1543 1543 1534 1534 1551 1551 1587 1587 1612 1612 818 843 RI7 817 83) 83:: 1158 1158 1174 1174 J..t 7G 1176 1191 1191 1207 1207 1228 1228 22 63 240 240 247 247 53)
28 )99 42 33 563 563 572 572 1000 1000 1010 1010 851 851 846 846 12)1 1231 1226 1226 836
2 4 6 8 10 12 14 16 18 20 22 24 26 28 )0 J2 34 36 38 40 42 44 46 48 50 52 54 !:6 58 60 62
5942 5)188 31520 39913 )991) 26371 26371 44685 44685 3114) 31143 42983 42983 29441 29441 41322 41322 27780 27780 51642 34544 37917 37917 27230 27230 41884 41884 31197 311 c,; 40435 4048!1 29798 29798 39121 39121
)
5 7 9
11 13
15 17 19 21 23 25 27
29 J1 J) 35 37 )S'
41 43
45 47 49 51 5) 55 57 59 61 63 65 67 69 11 73 15 77 79 81 83 85 87 89
~29 1~71
671 667 667 ~57
957 953 953 ',196 U.96 1192 11:12 1505 1506 1St:? lr.502
64
66 68 70
3)
32
327 327 329 329 644
31
72
28434
74 76 78 80 82 84 36 88 90
28434 13993 10578 13087 13037 10830 108)0 16863 HR63
UPLIFT FORCE
TRANS. FORCE
LONG. FORCE
-5942 -39115 -21560 -28780 -28780 -17809 -17809 -33467 -33467 -22496 -22496 -318)9 -31839 ' -20868 -20868 -30076 -)0076 -19105 -19105 -37569 -24584 -26821 -26821 -18706 -18706 -30742 -30742 -22627 -22627 -29403 -29403 -21288 -21288 -27957 -27957 -19841 -19841 8307 3495 3048 3048 -53 -53 -840 -84ft
577 1159 1502 1116 1116 1331 1331 1534 1534 1749 1749 1509 150'9 1725 1725 1597 1597 1812 1812 825 1162 824 824 1034 1034 1163 1163 1374 1374 1144
4 64 71 577 577 596 596 1013 1013 1033 1033 867 867 837 837 1245 1245 1215 1215 859 868 686 686 657 657 973 973 944 944 1212 1212 1183 1183 1520 1520 1491 1491 78 110 355 355 377 377 670 670
~.144
1366 1366 1218 1218 1428 1428 86 727 24', 249 655 655 552 552
AN~-9
CHEMICAL COMPOSmON AND MECHANICAL PROPERTIES OF MILD mEL Description
INDIAN
SAIL-MA (INDIAN)
BRITISH
AMERICAN
GERMAN
JAPANESE
IS- 2062
MA300HV
BS-436O GR-43A
ASTMA36
DIN-17100
JIs-G-3101
0.25
0.25
0.26
0.17.().20
1.50
1.60
Cl.ASS-2
Cbemlcgl Comoosltfon.
Carbon
...
0.23-0.25
Manga\eS8 ...
Phosphorus ...
0.055
0.05
0.04
0.05
0.05
SUlphur
...
0.06 0.06
0.055
0.05
0.05
0.05
0.05
SIlIcon
%
MfK:tK:Icls::CI
0.05
0.50
~[QQ£ll1la5
Tensile Strength kg/mm2 YIeld Strength kg/mm2 Elongatlon (mln)%
42-54
44.88-57.12
43.86-52.02
40.80-56.10
34.66-47.94
41-52
26
30.60
26.01
25.50
23.97
24-25
23
20
22
20-23
26
lE'r21
. ANNEXURE - 1 CHEMICAL COMPOSITION AND MECHANICAL PROPERTIES OF HIGH TENSILE STEEL Description
Standards Indian
Specn. Nos.
15-961 EF-540
15-85CX> FE-490HT
SAll-MA
.
Amer1can
Brtt1sh
350
SAIL-MA MA-410
BS-436O
ASTM
GRSOB
A-441
ASTM
A-572
Germon
Japanese
DIN 17100 ST-52
JIS-G-3101
Oass- 3 55-50
GR50
Class 4 5S-SS
Cbarnlccl CQrnccsltlQc Carbon %
0.20
Mn%
0.25
0.25
0.25
0.20
0.22
0.23
1.50
1.50
1.50
1.50
0.85 to 1.25
1.35
0.49
0.30
(.oJ
w
51%
0.20
0.30
1.60
S%
0.055
0.055
0.055
0.055
0.05
0.05
0.05
0.04
0.05
0.04
P%
0.055
0.05
0.055
0.055
0.05
0.04
0.04
0.04
0.05
0.04
49.98 to
49.98
55.08
49.98
49.98 49.47
45.70
to
52 to
55
62.22
62.22
67.32
63.24
36
34.68
35.70
41.82
36.21
35.19
35.20
64.26 35.19 to . 36.21
28 to 29
40 -41
20
20
20
19
20
18
18t021
20 to 22
16 to 19
14-17
Mechanical PropertieS TensUe Strength Kg/mm2 YIeld Strength kg/mm2 Elongotton (Mln)%
58
to
to
to
•
62
ANNEXURE - 11 SECTION UST EQUAL SECT10N COMMONLY USED FOR TOWERS. AS PER lS:aoa (PART-V)-1969 Stze
35x35xS 4Ox4Ox3 4Ox4Ox4 4Ox4OxS 4Ox4Ox6 45x45x3 45x45x4 45x45x5 45x45x6 5Ox5Ox3 5OxSOx4 5OxSOx5 . 5OxSOx6 55x55x4 55x55x5 55x55x6 6Ox60x4 6Ox6OxS 6Qx6Ox6 65x65x4 65x65xS 65x65x6 65x65x8 70x 70x5 70x 70x6 70x 70x 8 75x 75x 5 75x 75x6 75x 75x 8 8Ox8Ox6 8Ox80x8 80. x 80 x 10 9Ox90x6 9Ox90x7 9Ox90x8 9Ox90xlO
Sectional Area (em2)
3.27 2.34 3.07 3.78 4.47 2.64 3.47 4.28 5.07 2.95 3.88 4.79 5.68 4.26 5.27 . 6.26 4.71 5.75 6.84 5.00 . 6.25 7.44 9.76 6.77 8.06 10.58 7.27 8.66 11.38 9.29 12.21 15.05 10.47 12.22 13.79 17.03
Unit weight Centre of Ixx-Iyy (cm4) gravity (em) kg/mt.
2.60 1.80 2.40 3.00 3.50 2.10 2.70 3.40 4.00 2.30 3.00 3.80 4.50 3.30 4.10 4.90 3.70 4.50 5.40 4.00 4.90 5.80 7.70 5.30 6.30 8.30 5.70
6.80 8.90 7.30 9.60 . 11.80 8.20 9.59
10.80 13.40
1.04 . 1.08 1.12 1.16 1.20 1.20 1.25 1.29 1.33 1.32 1.37 1.41 1.45 1.51 1.53 1.57 1.60 1.65 1.69 1.73 1.77 1.81 1.89 1.69 1.94 2.02 2.02 2.06 2.14 2.18 2.27 2.34 2.42 2.46 2.51 2.59
3.50 3.40 4.50 5.40 6.30 5.00 6.50 7.90 9.20 6.90 9.10 11.00 12.90 11.00 14.70 17.30 15.80 19.20 22.60 19.76 24.70 29.10 37.40 31.10 36.80 47.40 38.70 45.70 49.00 56.00 72.50 87.70 80.10 93.00 104.20 126.70
Rxx (Rmed) Rvv (Rmin) Modulus of section (em) (em) (em3)
1.04 1.21 1.21 1.20 1.19 1.38 1.37 1.36 1.35 1.53 1.53 1.52 1.51 1.67 1.67 1.66 1.83 1.82 1.82 1.99 1.99 1.98 1.96 2.15 2.14 2.12 2.31 2.30 2.28 2.46 2.44 2.41 2.77 2.76 2.75 2.73
0.67 0.77 0.77 0.77 0.77 0.87 0.87 0.87 0.87 0.97 0.97 0.97 0.96 1.06 1.06 1.06 1.18 1.16 1.15 1.26 1.26 1.26 1.25 1.36 1.36 1.35 1.46 1.46 1.45 1.56 1.55 1.55 1.75 1.77 1.75 '1.74
1.40 1.20 1.60 1.90 2.30 1.50 2.00 2.50 2.90 1.90 2.50 3.10 3.60 2.96 3.70 4.40 3.58 4.40 5.20 4.16 5.20 6.20 8.10 6.10 7.30 9.50 7.10 8.40 11.00 9.60 12.60 15.50 12.20 14.20 16.00 19.80
ANNEXURE· l' SEcnON UST EQUAl SECT10NS COMMONLY USED FOR TOWERS AS PER 1$,&08 (PART -V)-1989 Size
Sectional
Area (em2)
UnIt weight kg/mt.
Centre of gravity
Ixx.~ (em
Rxx(Rmed) Rw(Rmln) Modulus of (em) (em) Section (em3)
(em)
100x 1oox6
11.67
9.20
2.67
111.30
3.09
1.95
15.20
lOOxloox7
13.62
10.70
2.71
129.00
3.08
1.97
17.70
100 x loox8
15.39
12.10
2.76
145.10
3.07
1.95
20.00
l00x 100 x 10
19.03
14.90
2.84
177.00
3.05
1.94
24.70
l00x loox 12
22.59
17.70
2.92
207.00
3.03
1.94
29.20
110x 110 x 8
17.08
13.40
3.00
196.80
3.40
2.18
24.60
110x 110 x 10
21.12
16.60
3.09
240.20
3.37
2.16
30.40
110x 110x 12
25.08
19.70
3.17
281.30
3.35
2.15
35.90
11Oxll0x16
32.76
25.70
3.32
357.30
3.30
2.14
46.50
120x120x8
18.70
14.70
3.23
255.00
3.69
2.37
29.10
120 x 120 x 10
23.20
18.20
3.31
313.00
3.67
2.36
36.00
120x 120x 12
27.Eil
21.60
3.40
368.00
3.65
2.30
42.70
130 x 130x 10
25.12
19.70
3.59
405.30
4.02
2.57
43.10
130 x 130 x 12
29.88
23.50
3.67
476.40
3.99
2.56
51.00
150x ISO x 10
29.21
22.90
4.08
635.50
4.66
2.98
58.00
150 x 150 x 12
34.77
27.30
4.16
746.30
4.63
2.97
68.80
150x lSOx 15
43.00
33.80
4.25
898.00
4.57
2.93
83.50
150x 150x 16
45.65
35.80
4.31
958.90
4.58
2.94
89.70
150x 150x 18
51.00
40.10
4.37
1050.00
4.54
2.92
93.70
150x 15Ox2O
56.21
44.10
4.46
1155.50
4.53
2.93
109.70
180 x 180 x 15
52.10
40.90
4.98
1590.00
5.52
3.54
122.00
180x180x18
61.90
48.60
5.10
1870.00
5.49
3.52
145.00
180xl80x2O
68.30
53.70
5.18
2040.00
5.47
3.51
159.00
200 x 200 x 16
61.82
48.Eil
5.56
2366.20
6.19
3.96
163.80
200 x 200 x 20
76.38
60.00
5.71
2875.00
6.14
3.93
201.20
200 x200x24
90.60
71.10
5.84
3333.00
6.06
3.90
235.00
2OOx200x25
94.13
73.90
5.90
3470.02
6.07
3.91
246.00
ANNEXURE • Sheet· I 0
L\1 CONSIOERAnON FOIIRACING SYSTEM IN A TRANSMISSION TOWER
CD{
-------- --------
~---
® VlEWI ,.,
ADIr •• or ~ AFJru or DC/r •• or ... ),[/r .... or CB/r •• or
• }'B/r•• or 9 )'8fr:,y
.AD/i.., or" AFJr~ .. 0' DC/r n or It Aftr • ., 01 (8Jr ..'# or .A.Ciru or .. Joe/r., II
liP SKA.CING
,.
A
11Dh.v or • A rfrre.,. DC/r n or CBJrn of "AE/r ...
OJ'
I
VIEW2·Z
----_. -.. _--------=-Af/t·./v or t AF Jr•• f!.i Ir ..... I'!r .. AE/r., .. D ::.jl.,.v
O(
ClJlrnt
• APPUCAnON FOR TENSION COMPRESSION SYSTEM ONLY I.e. TENSILE STRESSES IN ONE BRACING MUST BE AT LEAST EQUAL TO 75 PERCENT OF THE COMPRESSIVE STRESS IN THE OTHER BRACING. # THE CORNER STAY SHOULD BE DESIGNED TO PROVIDE LATERAL SUPPORT ADEQUATELY
at"
Or
ANNEXURE -1 Sheet-2 of
l \ RCONSIDERAOON FOR BRACING SYSTEM IN ATRANSMISSION TOWER
0{
~.
A
~
Sltfllitrriesl R4liD Ct';i.iui 01: X
ABlr,.,
1f'14IN')
y
~.
r 0~
~~,
l
L1* ,-1
IoC/.tyv
f1I
AB7ru
or
~ct.,,,
or
AD/r..,
or or
CBIt.,.,
or
C8
'I.,
A'/''fY
vaw
f)Cftvv
CBIt.,.,
G) HIP 8R ACING A-
or
A8/,x."
or
AD/r""
or
DC1'"" (8/,.,.,
or or
.~C/r~
or
AD/r w
Of
A8!'J)'
~C/r,'1
I.
DCt'"
or
~Elr.,.,
OT
DC/r.." C!fry.,
oy
CB r.,., '\.
HIP 8R "CINCO A A
0
EDlr.,.,
or
--_._~
THE
(ORNER ST~Y SHOULD IE DESICNEOfO PRov,tE l,ATEAAl SUP'Pl>R'I' AtEqUA'TF L1
ANNEXURf • 13 Sheet· 1of 5
PERMISSIBLE AXIAL STRESS IN COMPRESSION
CONSIDERATION FOR L/R OF COMPRESSION MEMBERS
-~----------~~--~----~--------------~-~-~---
The compressive stresses 1n various members multiplied by the appropriate factor of safety shall not exceed the value given by following formulae ( As per IS-B02 (Part-I) 1992). Fa
•
(-r~~~!jJ ry <~c y Il It; r- Wheu~ Where KL/r
& Fe- •
"-
(for b/t'Lim)
Cc (for
b~t
Fa
•
Allowable unit stress in compression
Fy
•
Minimum guaranteed yield stress of the material. (ly • 2549.3 kqlcm2 for Mild steel & Fy • 3620 kg/cm2 for High Tansile Steel).
Cc
•
125.664 for Mild Steel & Cc • 105.455 for High Tensile Steel.
kg/cm2)
13 for Mild Steel & 11 for High
(bIt) Lim • 661.8 Where b
(Kn
Tensile Steel. = distance from edge of fillet to the extreme fibre and t • thickness of material.
Where width thickness ratio
(bit) exceeds (bIt) lim, above
formula will reduce as follows and -Fy" for (I
: &
will be replaced by
For
~
For
., 668400 I (bIt) 2 where bit
4275 - 132 (bit)
where 13
<
<.. bit
> 24 <
For = 6070 - 2'-3 where 11 bit 20 & for = 668400 I (bit) 2 where bit> 20
<
24
"'~I
-.ioU! i;I
PERMtSSIBL! AXIAl. STRESS IN COMPRESSION FOR MILO STEEL FOR CURVE 1 IIr
39 40 41
42 43
« 45 46
47 48
40 50 51
52 53 ·54
55 56
57 58 59 60
81 62 63 64
65 68
67 68
69 70 71
72 73 74 75 76 77
78 79 CURVE 1:
Ko/cm'
2427 2420. 2414 2407 2400 2393 23M 2379 2371 2363 2355 2~8
2339 2331 2323 2314 2305 2296 2287 2278 2268 2259 2249 2239 2229 2219 220.8 2198 2181 2176 2165 215-4 2142 2131 2119 2107 2095 2083 2071 2058 2~
FOR CURVE 2
Vr 80 81 82 83
Kg/em'
64
1980
85
1966 1952 1938 1924 1910. 1895 1881 1866 1851 1836 1821 1805 1790 1774 1758 1742 1726 1710 1693 1676 1659 1642 1625 1608 1590 1573 1555 1537 1519
86
87 83
89 90
91 92 93 94 95 96
97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120
20.33 20.20 2007 1993
1500
1482 1~3
1444 1425 1406 1387
IIr
39 40 41 42 43 44 45 46 47 48 49 50
51 52 53
s.. 55 56
57 58 59 60
61 62 63
64
65 66
67 68 69 70 71 72 73 7. 75 76 77 78 79
Kg/cm
l
2266 2259 2251 22« 2237 2229 2221 2213 2206 2198 2190 2182 2173 2165 2157 2148 2140 2131 2122 2113 2104 2095 20.86 20.77 2068 2058 20492039 2029 2020 2010 2000
1990 1980 1970 1959 1949 1938 1928 1917
1906
IIr
80
81 82 83 84
85 86 81 88
89 90 91 92 93 94 95 96
97 98 99 100 101 10.2 10.3 104 10.5 106
107 108 109 110 111 112 113 114 115 1"16
117 116 119 120
FOR CURVE 3 Kg/cm
l
1895 1885 1874 1862 1851 18040 1828 1817 1805 1794 1782 1770 1758 1746 1734 1722 1710. 1697 1685 1672 1659 1647 1634 1621 160.8 1595 1581 1568 1555 1541 1528 1514 1500 1486 1472 1458 14« 1430 1416 1401 1~87
IIr
3Q 40 41 42 43 44
45 4e
47 48 4i 50 51 52 53 54 55 56
57 58
59 60 61
62 63 64 65 66
67 68
69 70 71 72 73 74 75 76 77
70 79
Kg/cm 2
203Q 2033 2026 2020. 2013 2007 2000 1993 1987 1980 1i73 1966 1959 1952 19045 1938 1931 1i24 1i17 1910 1903 1895 1888 1881 1874 1866 1859 1851 18044 1836 1828 1821 1813 1805 1798 1790 1782 1774 1766 1758 1750
TO BE USED FOR LEG MEMBERS' LAnlCES HAVING BACK TO BACK DOUBLE ANGLE FOR UR UPTO 12U
CURVE 2: TO BE USED FOR CROSS ARM MEMBEr~S (KUr • 30 + 0.75 UrI FOR lIR UPTO 120 CUlitVE 3:
TO BE USED FOR LAmCES WITH SINGLE ANGLE SEC1!ON FOR lIR UPTO 120
39
ptWpI
tlO. O.llk I
IIr
80
81 82 83 54
85 Be 87 88
89 go
91 92 93 Q.4
95
ee 97 98 99
100 101 102 103 104 105 108 107 10.8 109 110 111 112 113 114 115 116 117 118 119 120
Kg/~I
1742 1734 1728 1718 1710 1701 1Sla3 18&5 1878 1661 1859 16.51 1&4.2 1634 1825 1617 1608 1599 1590 1581 1573 1584 155.5 1546 1537 1528 1519 1SDe 1500 1491 1482 1472 1463 1~5-4
14« 1435 1425 1416 1406 1397 1387
ANNEXUR£ • 13
Sheet- 3 of 5 PERMISSIBU AXIAL STRESS IN COMPRESSION FOR MILO STEEL FOR CURVE 4 Vr
121 122 123 124 125 128 127 128 129 130 131 132 133 134 135 138 137 138 139 140 141 142 143 144 145 146 147 14a
Vr
Kg/cm~
Vr
Ka/cm
1375 1352 1330 1309 1288 1268 1248 1229 1210 1191 1173 1155 1138 1121 1104 1088 1072 1057 1042 1027 1012
161 162 163 164 18S
177 167 158 148 739 730 722 713 705 696 688 .680 673 665 657 650 642 635 628 621 614 608 601 595 588 582 576 570 563 558 552
121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 13e 137 138 139 140 141 142 143 1« 145 146 147 148 149 150 151 152 153 154 155 156 157 158
1379 1362 1345 1329 1312 1296 1281 1265 1250 1235 1220 1206 1192 1178 1165 1151 1138 1125 1112 1100 1088 1076 1064 1052 1040 1029 1018 1007
159
897 888
t66
796
167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 1M 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199
786
200
i&4
971 957 944
831 819 907 895 883 811 860
150 151 152 153 1~
155 156 157 158 159 160
KQltm~
998
,.9
8-'9 838
827 817
806 ,
FOR CURVE 5
~6 ~o
535 529 524 519 513 508 503
160
2
996
986 975 965 955 io45
835 926
916 ~7
Vr
161 162 163 164 165 166 187 168 1tiQ 170 171 172 173 174 175 116 177 178 179 180 181 182 183 1~
185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200
FORCURV!I Kalcm~
&80
871 862
e54 8045 837 829
821 813 605
797 790 782 775 767 760 753 746 739 733 726 719 713 706 700 6~
668 682 676 670 e&4
658
652 647 &41 63G 630
625 620 614
L'r
121 122 123 124 125 128 127 128 12V 130 131 132 133 134 135 138 137 131 138 140 141 142 143 144 145 148 147 148 148 150 151 152 153
Kglcm 2
13&4 1370 13~
1342 1329 1318 1303 12iO 1277 1265 1253 1241 1221 1217 1m 11~
1183 1172
".,
1150 1139 1129 1111 1108
1098 10M 1079 1069 1058 1~
155
1041 1032 1023 1014 1005
158
9ge
157 158
Me
~54
1~
160
9711 171 te3
CURVE 4:
TO BE USED FOR LATIICES HAVINQ 1 10LT CONN!c;TION FOR UK 120 TO 200
CURVE.:
TO B~ USED FOR LAmCES HAVlNG 110lT CQNNECTION AT ONI tNO AbO 2 10LT CONNECTION AT OTHER END(K~ 2'.1 "," .712 UrI FOR LJR1J1'1O 200
tURn I:
TO Bl USED FOR LATI1CES HAVlNG 2 BOLT CONNECTION Ai EITHER IND • . , • •_
......
a
....
1 . __ P"'-" I ,III ."""
'Y""'''""
Vr
Kglcm J
161 162 183
155
164
165 1e1 187 168 189 170 171 172 173 174 175 176 177 171 179 180 181 182 183 184 185 188 187 111
'" 190 181 192 1a3 1M
1" 11e 117 191 1" 200
94e
13i 131 123 115
eoe 900
893
eae
.. 171 171 .~
151 I« 837 131 124 "8 811 105 711
713 7.7 7a1 775 7et 183
757 751 748 740 735 721 724 718 713
7~J
703
PERMISSIBLE AXIAL STRESS IN COMPRESSION FOR HIGH TEN~LE STEEL ---FOR CURVE 1 FOR CURVE 2 FOR CURVE 3 IIr
39 ~O
41 42 43 44 45 46 47 48 49 50 51 52 53 54
55 56
57 58
59 60
61 62 63 64
65 66
67 68
69 70 71 72 73 74 75 76 77
78 79 CURVE l'
CURVE 2:
Kg/em!
3372 3360 3~6
3333 3319 3305 3290 3276 3260 3245 3229 3213 3197 3180 3163 31
Vr
80 81 82 83 84
8-5 86
87 88 89 90
91 92 93 94
95 96
97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120
Kg/em'
2578 2552 2526 2499 2472 2444 2416 2388 2360 2331 2302 2272
2242 2212 2182 2J51 2120 2089 2057 2025 1992 1960 1927 1893 1860 1826 1791 1757 1722 1686 1651 1615 1578 1542 1505 1468 1430 1392 1354 1315 1276
IIr
39 40 41 42 ·3 44 45 46 47 48 49 50 51 52 53 54
. 55 56 57 58 59 60 61 62 63 64
65 66
67 68 69 70 71 72 73 74 75
76 77
78 79
KQlcm 2
Ur
Kg/cm
l
IIr
3049 80 2302 39 3034 81 2280 40 3019 . 82 2257 41 3004 83 2235 ~2 2989 84 2212 43 2974 85 2189 44 2959 86 2167 45 2943 87 2143 46 2927 88 2120 47 2911 89 2096 48 2895 90 2073 49 2878 91 2049 50 2862 92 2025 51 2845 2001 93 52 282.8 94 1976 53 2811 1951 95 54 2794 96 1927 55 2776 97 1902 56 2759 1876 - 57 98 2741 1851 99 58 2723 1826 100 59 2704 1800 101 60 2686 1774 61 102 2667 1748 103 62 2649 104 1722 63 2630 105 1695 64 2611 106 1668 65 2591 107 1642 66 2572 108 1615 67 -1587 2552 109 68 ·69 2532 110 1560 1533 70 2512 111 2492 112 1505 71 2472 113 1477 72 2451 1«9 114 73 2430 115 1420 74 2409 1392 75 116 2388 117 1363 76 2367 1334 77 118 2345 '119 1305 78 2324 1276 79 120 .
Kglcm 2
2591 2578 2565 2552 2539 2526 2512 2499 248.5 2472 2458 2444 2430 2416 2402 2388 2374 2360 2345 2331 2316 2302 2287 2272 2257 2242 2227 2212 2197 2182 2167 2151 2136 2120 2104 2089 2073 2057 2041 2025 OQ09
TO BE USED FOR lEG MEMBERS' LArnCES HAVING BACK TO BACK DOUBLE ANGLE FOR UR UPTO 120 TO BE USED rOR CROSS ARM MEMBERS (KUr a 30 • 0.75 VI') FOR UR UPTO 120
CURVE 3:
TO BE USED FOR LATTICES WITH SINe ~ _ ANGLE SECTION (KUr: 80 .0.6 Ui , FOR UR UPTO 120
41
IIr 80
81 82 83 84 85
Sheet· 4 ot5
l
1992 1976 1960 1943 1927 1910
86
1893
,87 88 89 90 91 92 93
1878 1860 1843 1826 1808 1791 1774 1757 1739 1722 1704
94
95 96
97 98
16.86
99
1698
100
1651
101 102 103 104 105 106 107 108 109 110 111 112
1633 1615 1597 1578 156.0 1542 1523 1505 14.86' 14G.8' 1449 143.0 1411 1392 1373 13.54 1334 1315 1296 1276
113 114
115 116 117 118 119 120
•
AHNEXURl - 13 Sheet - 5 of 5
PERMISSIBLE AXIAL STRESS IN COMPRESSION FOR HIGH TENSILE STEEL FORCURve.c
IIr
Kg/cm
2
121 122 123 124 125 120 127 128 128 130 131 132 133 1)4 135 136 137 138 138 1-40 141 142 143 144 145 148 147 148 148 150 151 152 153
1375 1352 1330 1)(X1 12M 1263 1248 1m 1210 1181 1173 1155 1138 j121 1104 1088 1072 1057 1042 1027 1012 998 984 971 957
154 156
849 838 827
157 158 19 160
806 796 786
155
.944
831 818 907 895 883
871 860
817
IIr
161 162 163 1&4 165 166 167 168 169 170 171 172 173 174 175
176 177 178 179 180 181 182 183 1&4 185 186 187 188 189 190 181 192 193 194 195 196 197 198 199 200
FOR CURVE 5 Kg/em'
777 767 758 7048 739 730 722 713 705 696 688
680
673 665 657 650 642 635 628 621 614 608
601 595 588
582 575 570 563 558 552 5-46 5040
535 529
524 519 S13 508 503
IIr
121 122 123 124 125 126 127 128 1~
130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156
FOR CURVE I
KQlem l
IIr
Kg/em'
IIr
KQfcm J
1379 1362 1345 1329 1312 1296 1281 1265 1250 1235 1220 1206 1192 1178 1165 1151 1138 1125 1112 1100 1088 1076
161 162 163 1s.. 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193
880 871 862 8504 845 837
121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147
138<4 1370 1356 1342 1329 1316 1303 1290 1277 1265 1253 1241 1229 1217 1205 1194 1183 1172 1161 1150 1139 1129 1119 1108 1098 1088 1079 1069 1059 1050 1041 1032 1023 1014 1005 996 988 979 971 963
los.. 1052 1040 1029 1018 1007 996 986
975 965 955 945 935 926
~94
195 196
157 158 159
907 897
197 198 199
160
8S8
200
916
829
821 813 805 797 790 762 775 767 760 753 746 739 733 726 7" 713 706 700 694 688 682 676 670
·,48
6&4
658 652 647 641 636 630 525
i
I
149 150 151 152 153 1504 155 156
157 156
520
",59
614
160
CURVE 4:
TO RE USED FOR LATIlCES HAVING 1 BOLT CONNECTION' FOR UR 120 TO 200
CURVE I:
TO BE USED FOR LATIICES HAVING 1 BOLT CONNECTION AT ONE END AND 2 BOLT CONNECTION AT OTHER END(KUr= 2U + .112 UrI FOR UR 120 TO 200
\;URVE I:
TO BE USED FOR LATIlCES HAVING 2 BOLT CONNECTION~.T EITHER END IKI
Ir=.~ .,.
Ai" I/r\ J:nR I IR 11U TC 2110
Vr
KW'em'
161 162 163 1&4 165 166 167
955
168
900
169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186
893
9<46
939 931 923 915 908
886
879 871 864 858
851 &«
837 831 824 818 811 805 799 793 787 781
~87
775
188 189 190 191 192 193 194 195
769 763 757 751 746 740 735 729 72'719 713 -708 703
196
197 198 199 200
ANNEXU.R£ • ,. REFERENCE TAel£ FOR MAXIMUM PERMISSIBlE l£NGTH OF REDUNDANT MEMBERS Section
.
l/R CONSIDERAnONS
WIth Rw (R min)
BENDING CONSlDERAnoNS ONLY
WIth Rxx orRyy (Rmed)
WIth 100 Kgs. (Ultimate)
WIth 150 Kgs. (Ultimate)
H.T.
M.S. (2600)
(3600)
M.S. (2600
(3600)
H.T.
45X30X4
1575
2100
936
1296
624
864
45X30X5
1575
2075
11M
N.C.
763
1056
45X45X4
2175
3425
2080
N.C.
1387
1920
45X45X5
2175
3400
N.C.
N.C.
1733
N.C.
SOXSOX4
2425
3825
N.C.
N.C.
1733
2400
SOX5OX5
2425
3800
N.C.
N.C.
2149
N.C.
5OX5OX6
2400
3775
N.C.
N.C.
N.C.
N.C.
55X55X4
26Ei)
4175
N.C.
N.C.
2052
N.C.
55X55X5
26Ei)
4175
N.C.
N.C.
2565
N.C.
6OX60X4
2975
4625
N.C.
N.C.
2538
N.C.
6OX60X5
2900
A550
N.C.
N.C.
N.C.
N.C.
65X65X4
3150
4975
N.C.
N.C.
2884
N.C.
65X65X5
3150
4975
N.C ..
N.C.
N.C.
N.C.
65X65X6
3150
4950
N.C.
N.C.
N.C.
N.C.
70 X 70X 5'
3400
5375
N.C.
N.C.
N.C.
N.C.
75 X 75X5
3650
5775
N.C.
N.C.
. N.C.
N.C.
75 X 75X6
3650
5750
N.C.
N.C.
N.C.
N.C.
8OX80X6
3900
6150
N.C.
N.C.
N.C.
N.C.
9OX90X6
4375
6925
N.C.
N.C.
N.C.
N.C.
.Red. Members to be checked for 2.1/7'4 stress & bending independently.
N.C. =Not critical from bending COnsiderations. therefore.l/R lenghts to be used. Notes: 1. Maximum l/R for redundants should not exceed 250. 2. Intermediate stress values can be obtained by Interpolation. 3. Redundants considered with one bolt connection at either end. R MED
It
RMIN
1, SKETCH-1
R MIN
RMIN
f
I
1 SKETCH-2
J,
ANNEXURE - 15 Sheet No. 1 01 3
DIMENSIONS FOR HEXAGON BOLTS FOR STEEL STRUCTURES All dlmensJons In mlilimetres
Y according to IS: 1369-1961 -Dimensions for screw threads run-outs and undercuts·. 'z' according to IS: 1368-1967 -Dimensions for ends of bolts and screws (first revision)," Size
M12
M16
M20
M24
d
Nom
12
16
20
24
s
Nom
19
24
30
36
e
Min
20.88
26.17
32.95
39.55
k
Nom
8
10
13
15
r
Max
do
Max
15.2
19.2
24.4
28.4
20
23
26
30
b
r ,
'-"'lIll1""Vftl
Sheet: ULnMATE STRENGTHS OF BOLTS Bolts/Nuts conforming to IS : 6639 Mechanlcol Properties conform to IS: 1367 (FOR PROPERTY CLASS 1..6/1.)
=
Ultimate shearing stress 2220 kg/cm2 Ultimate bearing stress = 4440 kgl cm 2 Shearing Strength tor one bott
Bearing Strength for one batt (In kg)
Bottdia
..
--'T)
Single Shear (kg)
Double Shear (kg)
3mm
3.175 mm
4mm
5mm
6nm
7mn
(1/8")
12mm
2511
5022
1598
1692
2132
3197
4464
8928
2131
2256
2842
3552
-
373C
16mm
----
2664
4263
49n
20mm
6974
13948
2664
2820
3552
4440
5328
6216
24mm
10043
20086
3197
3383
4263
5328
6394
7460
(FOR PROPERTY CLASS 5.6/5) Ultimate shearing stress = 3161 kg/cm2 Ultimate bearing stress = 6322 kg/cm2
Bolt dia. (inmm)
Single Shear (kg)
12mm
Bearing strength tor one bolt (in kg)
Shearing strength for one bolt Double Shear (kg)
3mm
3.175mm
4mm
5mm
6mm
7mm
(1/8")
7150
2276
2409
3035
3793
4552
5311
16mm
-6356
12712
3035
3212
4046
5058
fJJ70
7081
20mm
9931
19862
3793
4015
5058
6322
7587
8851
24mm
14300
28&Xl
4552
4818
tlJ70
7587
9104
10621
3575
45
ANNEXURE - 15 Sheet 3 of 3 NOMINAL L£NGTHS' CLAM~NG1.ENGTHS FOR M12, M16, M20' M24 BOLTS AS PER IS - 6639-1972
Oesig. nation
Nominal lengths (Inmm)
Urn Weights and clamping lengths M12 Bott Unit
\
M24 Bott
M20 Bott
M16 Bolt
Grip lengths
Unit
wt.
Grip lengths
(kg)
(mm)
(kg)
(mm)
-
Grip Lengths
Unit
wt.
Grip lengths
Untt
wt. (kg)
(mm)
(kg)
(mm)
wt.
'.
A
35
0.062
10-14
0.117
6-10
-
-
-
B
40
0.0664
15-19
0.125
11-15
0.222
&-12
-
-
C
45
0.0708
20-24
0.133
16-20
0.234
13-17
0.369
9-13
0
50
0.0753
25-29
0.141
21-25
0.247
18-22
0.387
14-18
E
55
0.0797
3(}34
0.149
26-30
0.259
23-27
0.405
19-23
F
60
0.0842
35-39
0.157
31-35
0.272
28-:2
0.423
24-28
G
65
0.0886
4Q.44
0.164
36-40
0.284
33-37
0.440
29-3.3
H
70
0.0930
45-49
0.172
41-45
0.296
38-42
0.458
34-38
J
75
0.0975
50-54
0.180
46-50
0.309
43-47
0.476
39-43
K
80
0.1020
55-59
0.188
51-55
0.321
48-52
0.494
44-48
l
85
0.1070
60-64
0.196
56-60
0.334
53-57
0.511
49-53
M
90
0.1110
65-69
0.204
61-<>3
0.346
58-62
0.529
54-58
N
95
0.1160
70-74
0.212
66-70
0.358
63-67
0.547
59-<>3
P
100
0.1200
75-79
0.220
71-75
0.371
6a-72
0.565
64-68
SPACING OF BOLTS AND EDGE DISTANCE ON FINISHED MATERIAL
Bolt Die.
Thickness of Spring Washer
Hole die.
Bolt Spacing
Edge distance (Min) Hole Centre Hole Centre to Rolled or to sheared or Flame cut Sown.edge. edge. (mm) (mm)
Weight kg
Thickness
(mm)
(mm)
(mm)
(mm)
12
0.004
2.5
13.5
32
16
20
16
0.009
3.5
17.5
40
20
23
20
0.Q15
4.0
21.5
48
25
28
24
0.026
5.0
25.S
60
33
38
Transmission Line Manual Chapter 8
Testing of Towers
CONTENTS Page
8.1
Introduction
8.2
Testing Requirements
8.3
Description of a Tower Testing Station ,
1
8.4
Calibration
2
8.5 . Assembly of Prototype Tower
:2
8.6
Rigging Arrangements and Location of the Loadcells
:2
8.7
Test Procedure
2
8.8
Testing of Prototype Tower
2
8.9
Special Requirements
3
8.10 Acceptance of Test Results
4
8.11 Material Testing
4
CBIP MANUAL ON TRANSMISSION LINE TOWERS CHAPTER-8 TESTING OF TOWERS
8.1
INTRODUCTION
Transmission line towers are highly indeterminate structures. In the analysis of design of these structures and their detailing a number of theoretical assumptions are made. The structures are mass produced and the quality of materials, fabrication and the assembly require checking. It is desirable that the Designers and Users both are convinced that the tower can stand the most critical loads for which it is designed and are therefore subjected to a full scale prototype test. For a Prototype test, the material used shall be made to the same standards, as those that will apply to all towers during mass production.
8.2
TESTING REQUIREMENTS
This full scale testing of tower is generally termed as Prototype Test and for conducting Prototype tests, a tower testing station is required where it is possible to measure the applied loads and deflections and observe the behaviour of the tower on application of the external design loads.
8.3
DESCRIPTION OF A TOWER TESTING STATION
Figures 1&2 give layout for "Typical Tower Testing Station" and "Rigging Arrangements" for applying test loads respectively. A Tower Testing Station shall consist of: (i)
A Test Bed to withstand maximum possible compression and uplift loads and shear resulting from the external loads on a prototype tower with the highest voltage and no. of circuits, which has to be subjected to testing at the Testing Station.
(ii)
Permanent Anchors of adequate capacity to take the Transverse, Longitudinal and Vertical Pulls applied to the tower of maximum expected width, height and strength proposed to be tested on a test bed. Longitudinal Mast (P) is a structure of adequate dimension and height, constructed at a sufficient distance from the tower bed and equipped with all Rigging arrangements for applying longitudinal loads. The Transverse loads are applied through pulleys positIoned on the Transverse Mast (B). Vertical loads are applied by means of dead weight or through anchors on the test bed.
(iii)
The arrangements for applying the combination of given loads at a specified rate of increase, if . required with the help of a Multi Sheave Pulley, to take mechanical advantage and reduce load on the winch. .
(iv)
Electrical Winches operated by remote control from a Central Control Room used for applying loads at the different points of tower structure, as far as possible simultaneously.
Instruments used for recording the load applied are either Mechanical Spring Gauges or Electrical/Electronic TransducerslDynarnometers. The dials of the respective Dynarnometersrrransducers indicate the load in the
particular wire. Transverse & longitudinal positions on the tower.
deflec~;t~~taken by TheOdolites on scales fitted at appropriate
(v)
Remote control of loading mechanisms.
(vi)
Remote and precise reading of measuring instruments, like Mechanical Spring Gauges or ElectricaVElectronic Transducers!Dynarnometers.
(vii)
Arrangement for calibration of the measuring instruments. From control room, the winches and the dynamometers are operated/controlled Control room shall have the facility to have the complete view of transverse and longitudinal testing arrangements of the test tower. All the electrically operated machines and instruments shall be connected to and controlled from the Control Room.
8.4
CALmRAnON
In order to ensure the correctness and reliability of all measuring instruments and in turn the validity of the
tests the calibration of all instruments before the test is conducted. Calibration of the load cells is done with either a Universal Testing Machine or by standard weights. In case the calibration is done with the use of UTM, the UTM shall be periodically (once in every six months) calibrated by an external third party. A typical calibration chart is shown in Appendix-I.
8.5
ASSEMBLY OF PROTOTYPE TOWER
The Prototype tower,fabricated as per structural drawings approved by the Purchaser shall be assembled and erected on a flxed base. Fitrnent of any member shall be easy, natural and shall not be a forced one. The Bolts should be tightened simultaneously on all four faces.
8.6
RIGGING ARRANGEMENTS AND LOCATION OF THE LOAD CELLS
To enable application of the external loads in the most representative manner and to simulate tower design conditions, the tower structure i~~gged suita~ly. Impact of any variance in inclination of rigging wires with respect to the directions accountedJ...in designs 15 considered while preparing Rigging Chart. Loads are applied as per these approved rigging charts: The loadcells shall be attached to the tower through the rigging wires, positioned as close as possible to the test tower so that frictional losses do not cause impact on the 10adcell:..
8.7
TEST PROCEDURE
1
The Prototype Tower is erected on the test bed and all the rigging arrangements are completed. The Tower is examined carefully to see that all the bolts and nuts are tightened properly. The tower is made truely plumb and square. All its members are checked for freedom from any visible defect. Two graduated metallic scales are fixed at Peak and Top Crossarm level on the transverse face. Readings on these scales with reference to the plumb line are taken by Theodolite.
8.8
TESTING OF PROTOTYPE TOWER
8.8.1
Bolt-Slip Test
In order to eliminate as far as possible, the play between the bolts and the holes throughout the structure, Bolt take up test is done in the beginning. Under this test all the transverse and vertical loads arc increased
~.9.
LOADED conditions. The loads on the tower are then reduced to zero or to as Iowa value as possible. The deflection reading is once again taken for this Zero loading. The differences between the two zero loadings are the permanent deflections on tower. For subsequent test purposes, the readings with zero loads taken after the Bolt Slip Test taken are considered as the Initial readings.
8.8.2
Sequence of Test Loading Cases
Sequence of test loading cases shall be pre-determined. The choice of the test sequence shall largely depend upon simplification of the operations necessary for carrying out the test programme.
8.8.3
Details of Tests
Test 1: (Brokenwire Condition) Security and Safety Conditions as well as Anti-cascade conditions Under this condition (all conditions involving longitudinal loads in addition to the transverse and vertical loads) all the transverse and vertical loads are first increased to about 100%. Longitudinal loads are then increased in steps of 50%-75%-90%-95% of the ultimate loads. At all stages of loading it shall be ensured that the transverse and vertical loads are not less than the values for corresponding step of the longitudinal load. At each step the loads are maintained for one minute and the deflections are noted. All loads are then increased to 100%. At this final 100% loading stage, tower is observed for 2 minutes and deflections are noted. The tower is required to withstand these loads without showing any failure. Mter every test the loads are brought down and deflection readings are taken for no load condition. Test-2: (Normal Condition) Reliability Condition: These loads are applied as far as possible simultaneously at all points in steps of 50-75-90 & 95%. The waiting period of one minute shall be maintained at each step. The waiting period at the final 100% loading stage shall be 2 minutes. Throughout the process of loading under all tests, the tower shall be closely observed for any visual sign of deformation. Whenever such deformation is observed, the loads shall be brought down and remedial measures shall be taken. It is pointed out here that the tendency of bowing in bracings shall not be considered as a sign of failure even though it is during the final waiting period. Test-3: Destruction Test: If no Destruction Test is required by the Purchaser the loads on tower after 100% under Test-2 above, shall be gradually brought down to zero. If desired by the Purchaser, in continuation to test 2, after the final waiting
period, the transverse loads only are increased in steps of 5% till the failure occurs. The Destruction test, however, can be discontinued beyond a certain limit on mutual agreement between the Purchaser, Design & Testing Station Authority. The point of failure is detected from the sudden drop of load indication in the instrument dials in the Control Room.
8.9
SPECIAL REQUIREMENTS
8.9.1
The test tower shall be black or galvanised tower as desired by Purchaser.
8.9.2
The tower which has been tested shall not be part of supply and is not to be used on line.
8.9.3
Test tower shall be provided with unbraced portion of stub equivalent the point of connection of bracing with leg.
8.9.4
During the process of tower test. when a nwnber of tests have been completed satisfactorily and a failure occurs at a subsequent test. the design will be reviewed and tower will be reinforced. if required. The reinforced tower will be put to test again and subjected to balance tests. unless the fail~e is of major nature. which will require all the tests to be repeated. or as mutually agreed between the Purchaser and the Supplier.
8.9.5
Application of Loads on Test-Tower
to
distance of chimney top to
As considered in design: 8.9.5.1 Transverse longitudinal and vertical loads. At peak and respective crossarm points. 8.9.5.2 Wind Load on Tower Body (i)
Wind load from top at peak and respective crossarm points upto bOllom cross-arm will be simulated suitably at ground-wire, Top cross-arm, Middle cross-arm and BOllom cross-arm levels.
(ii)
Wind loads on tower below bottom cross-arm will be simulated to act at boltom cross-arm point and test will be carried out accordingly.
(iii)
For tower with extension. wind load on extension will be simulatcd on Top of Extcnsion.
8.10
ACCEPTANCE OF TEST RESULTS
Test is considered as passed, if tower is able to withstand the specified ulLimatc loads (100% step) with no visible sign of deformation for the specified waiting period. A detailed report incorporating test data and the results of complete tests along with photographs of the tower shall be prepared by the test-authority. in quadruplicate.
8.11
MATERIAL TESTING
Material of the prototype shall be checked for mechanical and chemical charactcristics. Samplc sclectcd by the Purchaser from Test Tower shall be subjected to such tests. 9.11 PRESENTATION OF TEST RESULTS
The test report shall include the following data: 1.
The type of tested tower.
2.
The name and address of the tower manufacturer and of the tower designcr.
3.
The name and address of the client.
to
5.
The names of persons presented during the tests.
6.
A list of various assembly and detail drawings related to the tower tested with updated modifications of the drawings referred to.
7.
A schematic line diagram of the tower showing the various load points and directions of loading to
Ia
he
be applied and a table with the specified loads.
:ell
8.
Diagram showing the rigging arrangement used to apply the test loads.
9.
One table per test showing the loads required at the various points on the structure and for the various loading steps.
10.
One table per test showing the various deflection values measured.
11.
Results of Mechanical and Chemical Test carried out on samples taken from the tower.
12.
In the case of failure: A table showing the maximum loads applied to the structure just before the collapse; A brief description of the failure; The dimensional and mechanical characteristics of the failed elements.
13.
Photographs showing the whole of the structure and, details of the failure.
no
vcr
by
5
APPENDIX - I
CALI BRA TION CH ART Calibration of Moster Load Cell tDesk No. ) with Universal Testing Machine on for the testing of Tower Type M kd. of Moster Load Cell Number : U T M - Universal
Testing Machine.
U.T.M. Reading
1000 2000 3000 4000 5000 6000 7000 6000 9000
10000
( kgs) Moster Load Cell Reading Calibration of all the load cells l used for testing of tower in series with respect to master load cell. Moster Load Cell
Reading in kg. 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Load Cell No. I No. 2 No. 3 No.4 No. 5 No. 6 No. 7 No. 6 No.9 No.IO No.11 No. 12 No.13 No.14 No. 15 No.16 No.17 No.IS No.19 No.20 Witnessed by :
-. ....
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.
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.
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----
- - -
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-
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LAYOUT
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OF
,--cr----: T ,
i~,
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® ___
I
I
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I I
I
,
~
TEST
---
---
----~---
BED
FIG. I
A
MAIN TEST BED
B
TRANSVERSE MAST MAIN (60.0 M HT)
C
LOAD CELL ROOM
D
OFFICE BUILDING/CALIBRATION ROOM
E
TRANSVERSE ANCHORS
c:::=::=_-
PULLEY BLOCK
,---
G
WINCHlWINCH HOUSE (ACCOMMODATING ELECT. MOTORS)
I
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-
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-
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OBSERVATION CABIN
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MAINTENANCE SHED ERECTION MAST
N
LONGITUDINAL ANCHORS
P
LONGITUDINAL MAST
0
R
SECURITY OFFICE
C?
S
DIESEL GENERATOR SET
... 0
I I I
ERECTION WINCH STORE AREA
;=;-
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_______________________________________________________________
~
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FIG. 2
TYPICAL RIGGING ARRANGEMENT FOR TOWER TESTING
I
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400 A~E
NSIO'-I!j
IN
rnm.
E'( ON TRANS· MAST 4.00""",.0110.· ERECTION
""_';..cR:..;E=-_ _ __
GROUND WIRE (G.W.) (R)
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'2'3613"
T·C.( L)
3·2':1?'l"
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MIDDLE CONDUCTOR (M.e.)(R)
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BOTTOM CONDUCTOR (B.e.) (L)'
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or: TF: F.T To W E R
CENTRE LINE OF TRANSVERSE MAST
68000 TRANSVERSE MAST
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Transmission Line Manual Chapter 9
Materials, Fabrication, Galvanising, Inspection and Storage
I ,I ,I
Er
CONTENTS Clause Scope No. 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9
Page
Scope Material Quality Control Specific Requirements of Fabrication Operations in Fabrication Tolerances Shop Erection/Proto-type Tower Assembly Galvanising Inspection Packing and Storage.
1
1 1 3 4 5 5 5 5
Annexures I Chemical Composition and Mechanical Properties of Mild steel II Chemical Composition and Mechanical Properties of High Tensile steel III (a) Properties of Equal Angle Sections as per IS: 808 (Part V)-1989 (b) Properties of Unequal Angle sections as per IS: 808 (Part V)-1989 (c) Properties of Channel Sections IV Unit Weight of Plates V Dimensions of Hexagon Bolts for steel structures VI Ultimate strength of Bolts VII Properties of Anchor Bolts. Metric Screw Threads as per IS: 4218 (Part-3)-1976 with ISO
7 8 :9 11 12 13 14 15 16
Appendices Appendix I - Quality Assurance Plan I. Introduction II. Quality Objective III. Quality Policy IV. Organisation of Quality Control Department V. Quality Planning VI. DeSign and Drawings VII. Company standards VIII. Control on Inspection-Equipments!Tools/Gauges IX. Material Management X. Incoming Material Inspection XI. Pre-production XII In-Process Inspection XIII. Inspection and Testing of Finished (Galvanlsed) Material XIV.Storage, Packaging and Packing
17 17 17 17 17 17 18 18 18 19 19 21 21 25 26
Enclosures-A Sampling Plan for Incoming Material
27
a. Sections, Accessories and Brought out Material b. Sampling Plan for Physical Properties of Bolts, Nuts and Spring Washers
iii
27 37
Page c. d. e. f. g. h. I.
Sampling Plan for Galvanising Tests for Threaded Fasteners Formats for Inspection Report for Steel Stacklng/Prellmlnary-(QCD-I) Format for Report on Bend Test Format for Report on Testing of Physical Properties Format for Inspection Report for Bolts/Nuts-(QCD-2) Format for Test Report for Physical Properties of Bolts Format for Test Report for Physical Properties of Nuts J. Format for Inspection Report for Spring Washers-(QCD-3) k. Format for Inspection Report for Accessorles-(QCD-4) I. Format for Inspection Report for Steel Test Towers-(QCD-5)
28 29 32 33
34 36 38 39 41 42
B. Sampling Plan for" In-process Material (a) Procedure (b) Format for Quantity Control Report (c) Format for Loading Report of Crates (d) Format for Inspection and Loading Report of Fabrication Shop (e) Format for Inspection and Loadlang Report of Model Assembly <0 Format for Inspection and Loading Report of Model Shop. (g) Format for Out-right Rejection Slip (h) Format for Rectifiable Rejection Slip (I) Format for Weekly Records of Shlttwise Acid Strengths 0) Format for Galvanising Process !nspectlon Report (k) Format for Galvanising Inspection Report (I) Format for Testing Concentration of Prefluxing and Degreaslng solutions
43 43 44 45 46 47 48 49
Appendix 11 : Ust of Machines required for a well-equipped Tower Fabricating Workshop Appendix 111 : Workshop Chart Appendix IV: Process Flow Chart for Fabrication of Tower
56
50 51 52 53
55 57
58 (
r. c
c
, )
11 .J( '!'r
.. th , 411 '..• \1
iv
1
CHAPTER - 9 28 _9
MATERIALS, FABRICATION, GALVANISING, INSPECTION AND STORAGE
~2
33
4
16 J8
9.1 SCOPE
"'9 41 -12
This chapter covers the provisions relating to the materials, fabrication, galvanising, Inspection and storage requirements of Towers: 9.2 MATERIAL QUALITY CONTROL
43 44
45
16
47 -18
"9 SO )1 ~2
63 ')5
-.>6 ~7
58
Various grades of steel used In towers-detalls of sections, bolts and nuts and other accessories, need a detailed scrutiny and quality control procedure before being processed for fabrication, assembly etc. Annexures I and II give chemical composition and mechanical properties of mild steel and high tensile steel used In towers. Annexure 1\1 (a) to (c) gives sectional details and properties of hot-rolled angle and channel sections. Annexure IV gives unit weights of plates of all sizes. Annexures V and VI give dimensions of hexagon bolts and their mechanical properties respectively. Annexure VII gives the properties of anchor bolts. A weil-planned and executed quality assurance programme Is necessary to ensure delivery of acceptable material In a timely manner. Appendix I Is a typical quality assurance plan giving details of the various processes. Indicating process controls and various steps that are followed progressively at various stages of production to ensure right product as per the speCification. 9.3 SPECIFIC REQUIREMENTS OF FABRICATION
i
9.3.1 Reliability of a transmission structure depends not only upon Its design, but also on the development of structural arrangement. detailing of connections, uniformity of quality of structural sections, and accurate fabrication. Proper fabrication while maintaining permissible tolerances. and galvanIsing of towers are, therefore. very essential. The design of structure must be practicable rather than exact so that It Is done as Fabrication assignment. Maximum efficiency In fabrication of structural steel by Modern shops Is entirely dependent upon close co-operation between office, draffing room and shop. 9.3.2 Structural Assembly Drawings
After design Is complete, the structural assembly drawings should be prepared according to IS : 6961972 and IS: 962 -1967. The drawings shall show the complete design dimensions, member length, slope factors or triangles, section sizes, bend lines. gauge lines, diameter, length and number of bolts, spacers, washers. sizes of gusset plates, position of holes, etc., and relaffve location of various members. Sufficient number of elevatton. cross-section and plan views should be presented to cle.arty Indicate the details of joints and arrangement of members. All members should be clearly shown and respective Identification mark allotted to each member. . \.
The drawings should be drawn to a scale Idrge enough to convey the Information adequately.
All connections should be detailed to minimise eccentricity of connections. Due consideration should be given to the additional stresses Introduced in the members on account of eccentricity of conl')~ctlql')s. Dimensions of all members and on a member the distances such as hole-to-hole, length, gauge distance etc. should be given in full Integers and not in decimals. 9.3.3 Shop Drawings
r
Shop drawings, containing complete information necessary for fabrication of the component parts of. the structures should be prepared. These drawings should clearly st lOW the member sizes, length and marks, hole positions, gauge lines, bend lines, edge distances, amount of chipping, notching etc.
c
For Gusset fabrication, separate Individual itemwise templates can be made to facilitate gusset fabrication as well as Inspection. In case of members to be bent, shop drawings should Indicate the provisions for variation In length. At the design/drawing stage itself, care should be taken to see that the degree of bend given in any member Is such that neither flange width nor thickness shall vary beyond permissible limits for the section.
,).'
Items requiring steep bends can be cut and welded as per approved welding procedure.
01
9. :t
"'E )1
Each fabrtcator or detailer has his own method of preparing details. This method is generally an evolution process based on his equipment. facilities for material control, handling and shipping/transport procedures. It is not recommended that specifications be established in so far as actual bending details are concerned. However, at the time of proto stage/tower testing Itself, specific bend gauges and templates to locate the holes after bending must be established for the items to be bent.
be ~r
All 3
-M
9.3.4 Bill of Material Bill of material for each type of tower should be prepared separately. This should Indicate grade of steel, mark numbers, sections sizes, member lengths, their calculated weights, number of bolts, nuts and washers and their sizes, total quantities required and structural drawing numbers.
No reduction in weight due to drilling, punching of bolt holes, skew cuts, chipping, notching, chamfering etc., should be made while computing calculated weights of the members. All steel sections used should be as per IS :1852-1985 and all angle sections should have dimensions as per IS: 808-1989. In case more than one grade of steel is used in the structural members, proper Identification marks of vanous grades of steel being used should be made on the matenal to ensure their ultimate use in proper location in the tower before taking up fabncation. This may be achieved as follows:At the time of procurement of steel other than that conforming to IS: 226-1975, green colour on the edges of HT material on both sides Is applied so that there is no mix-up of MS and HT steel In stock yard as well as in the shops. A distinct green colour patch is maintained throughout and on the shop sketch also, HT steel marking is added for identifying high tensile steel items. This way, It is ensured that no mix-up of MS and HT steel materials can take place.
9.3.5 Cutting Memo In Fabrication Shop, several tower projects are taken up together. For each project, several types of towers in different quantities have to be fabricated. For each type of tower , number of sections may vary as per design and in length. IngenUity in planning with the help of computer for preparing
In de IS~ .J.
All 0 rr T posit th",,~c
to ~"l. 2
.
JIl
riclty
cutting list/memo leads to optimising wastage of raw materials as well as achieving completion of tower fabrication as per commitment.
luge
9.4 OPERATIONS IN FABRICATION
I
9.4. r Straightening: All material should be reasonably straight and, If necessary, before being worked, be straightened and/or flattened by pressure and be free from twists. straightening should not damage the material. Adjacent surfaces of the parts when assembled should be In close contact throughout keeping In view the tolerances specified. Machines used for straightening are:-
of ("1l')d
(1) For angle sections upto 110 x 110 x 10 mm-Roller Straightening Machine;
(2) For higher sections - Beam bending machine and Hydraulic Press. lsset :. .ie )~~e snail
9.4.2 Cutting: Cutting may be effected by shearing, cropping, flatne cuttlng- or sawing. The surfaces so cut should be clean, smooth and reasonably square and free from any distortion. 9.4.3 Bending: Mild steel angle sections (15:226-1975) upto 75 x 75mm (thickness upto 6 mm) shall be bent cold upto and Including bend angle of 10 degree; angles above 75 x75 mm (thickness upt6 6 mm) and upto and Including 100 x 100 mm (thickness upto 8 mm) may also be bent cold upto the bend angle of 5 degree. PI III other angle sections not covered above should be bent hot. All plates upto 12 mm thickness should be bent cold upto bend angle of 15 degree. Greater bends and/or other thicknesses should be bent hot.
Jl10n ;: )rt 3talls L,. Id
\<
All HT Steel sections should be bent hot. All bent material should be alrcooled. The bends should be of even profile and free from surface damages. The machines used for bending are: -Mechanical Presses, Hydraulic Presses and Beam Bending Machines. . 9.4.4 Punching and Drilling: Punching may be adopted for sections upto 12 mm thick. For thicker sections, drilling should be done. Holes In the members should either be drilled or punched to jig and should not be formed by flame cutting process. The edge security and bolt gaug.es as given below should be maintained In all cases.
)f
nuts ling,
EDGE SECURITY AND BOLT GAUGES
I _,') tp~1
lOut
lr "
"
pAS On5 .\.~
.,
Bolt dla (mm)
Hole dla (mm)
Pitch Min. (mm)
12 16
13.5 17.5
20 24
21.5
32 40 48
26.0
60
Edge security Hole centre to Hole centre to rolled edge (mm) sheared edge (mm) 16
20
20
23
25
28
33
38
. In determining gauge lines, allowances should be made for the mill tolerances In accordance with . IS: 1852-1985. Gauge line and edge security shall be determined from the heel end of angle sections.
All burrs left by punching or drilling should be removed. The holes near the bend line of a bent member on both sides of the bend line should be punched/drilled after bending and relative positions of these holes should be maintained with the use of proper templates/Jigs and fixtures and . the same templates/jigs should be used for Inspection of such Items. In case of disputes, with respect to fabrication tolerances, such Items may be approved after assembly of such members as per 3
structural drawings of that particular portion. The machines used for above purpose Including notching operation are:(1) Heavy-duty Cropping Machine;
(2) (3) (4) (5) (6)
Light-duty Cropping Machine; Light-duty Punching Machine; Heavy-duty Universal Machine; Heavy-duty Radial Drilling Machine (for drilling); Gas Cutting Sets-may be mechanically guided or manually set-type; (7) Circular Saw (for sawing).
9.4.5 Marking: The Identification mark allotted to the member should be distinctly marked before galvanising with marking dies of 16 mm size. The machine used for this purpose Is Eccentric Press. Workmanship and finish should correspond to the best modern workshop practices and all similar ports should be made Interchangeable. 9.5 TOLERANCES
9.5.1 Tolerance. in Holes 9.5.1.1 Holes for bolting should be cylindrical. The diameter of hole Is equal to diameter of.bolt + 1.5 mm for bolts upto 20 mm In diameters. For 24 mm dla bolts. the clearance between bolt shank and hole Is 2 mm. For higher sizes. the hole diameter Is· specified by the designer. While deciding the diameter of the hole whether drilled or punched. care should be taken In making allowance for thickness of galvanising coat on bolts as well as In the holes and for the tolerance In bolt shank diameter. It has been observed after series of measurements on bolt shanks that their diameter varies upto 0.3 mm above the nominal diameter. Thus. the final diameter of the holes to be punched/drilled at Black stage will be 1.5 mm + bolt diameter + 0.3 mm for bolts upto 20 mm In diameter. For 24 mm dia bolts. the final diameter of the hole at Black stage will be equal to bolt diameter + 2 mm + 0.4 mm.
e
1
s
9.5.1.2 Blocking of mis-punched/excess holes: Mispunched or excess holes not more than one on anyone cross-sectional area should be blocked by proper welding technique by qualified welders. Total.number of such blockings by welding may be limited to three holes In a member. No new holes should be permitted overlapping the plugged hole. The welding must be of proper quality and specification to ensure that strength of the welded member shall be not less than that of the normal member.
" ),
1 ftr ..II
9.5.2 Fabrication Tolerance. (a) On straightness (camber) - 0.4% of the length of sections of sizes upto 100 x 100 mm. - 0.2% of the length of sections of sizes over 100 x 100 mm. (b) The maximum allowable difference In diameter of the holes on the two sides of plate angle shall be 0.8 mm; I.e.. the allowable taper In a punched hole shall not exceed 0.8 on diameter. (c) On overall length of angle members : ± 2 mm (d) On consecutive holes : ± 1 mm (e) On 1st hole to last hole In member : ± 2 mm 4
"
or...~
"re $n( ,(
.•. the hIe I'
l
ma
On gauge distances : ± 1 mm (g) On specified hole diameters on the punch side : ± 0.3 mm (In black) or where drilled - 0.0 (f)
The fabrication tolerances In general shall conform to IS :7215-1974. In case of deviation beyond prescribed tolerance, the assembly of the members may be made as per Structural Drawings and If the overall dimensions of the structure are within limits, such Items can be accepted. For leg member lolnt holes, a manufactured cleat may be taken at random and placed over the member. The bolt should pass at right-angie to the surface of member. For comer cuts, notches, flanged cuts etc., a tolerance of ± 2 mm Is allowed. Appendix II gives a list of the Machines required for Tower Fabrication Workshop and Appendix III Is a workshop chart listing the Workshop Operations. Appendix IV gives Process Flow Chart for Fabrication of Towers. .
·...
9.6 SHOP ERECTION/PROTO-TYPE TOWER ASSEMBLY steel work should be temporarily erected In horizontal or vertical position (one tower of each type Including combination of leg extension/body extension) so that accuracy of members can be checked before testing the towers or commencing mass fabrication as applicable. The proto assembly Is done on the basis of approved structural drawing and shop drawings. 9.7 GALVANISING
,
...
r
s. A
y
e
)r
r
The tower members, bolts/nuts and other accessories should be hot-dip galvanlsed and the spring washers electro-galvanlsed. Galvanising should be done In accordance with IS : 2629-1985, after fabrication and the Inspection at black stage Is complete. The nuts may be re-tapped after galvanising so that these are "hand-free" on the galvanlsed bolts. The galvanising procedure and Its In-process Inspection are given In -QAP"(Quallty Assurance Plan)-Appendlx I . The galvanising bath should be reasonably free from dross. Chemically cleaned steel (after pre-treatment) should be dipped In molten zinc carefully.On removal from the kettle the galvanlsed material may have excess spelter which may be removed from the surface by bumping or Wiping. The temperature of the spelter In the kettle shall be control.led within close limits by means of accurate pyrometers.
9.8 INSPECTION This Is also covered In -QAP'" Appendix I. The Inspector has to be given free access at all reasonable time to those parts of the Manufacturer's works which are concemed with the fabrication of steel work and has to be afforded all reasonable facilities for satisfying himself that the fabrication Is being done In accordance with the provisions of the relevant standards/QAP. In general, all measurements are done with steel winding taps In accordance with IS : 1270-1965. The defects which may appear through fabrication, should be made good with his consent and according to the procedure laid down by the Inspector. All gauges and templates necessary to satisfy the Inspector should be supplied by the manufacturer. The grade and quality of steel used by the manufacturer should be correct. To ascertain the quality of steel used, the Inspector at his discretion may get the material tested at a suitable or approved laboratory. For Inspection of galvanlsed materiaL the manufacturer should provide galvanlsed coupons enabling the Inspector to carry out tests on the coupons. The coupons should be taken from the batches corresponding to the fabricated material under Inspection. 5
9.9 PACKING AND STORAGE Angle sections may be wire-bundled or loose as may be mutually agreed upon. Cleat angles, gusset plates, brackets, fillet plates, hangers and similar loose pieces may be nested and bolted together In mUltiples or securely wired together through holes. Bolts, nuts, washers and other attachments should be packed In double gunny bags and accurately tagged In accordance with the contents.The packing should be such as will avoid losses/damages during transit. Each bundle or package should be appropriately marked.
6
ANNEXURE I CHEMICAL COMPOSmON AND MECHANICAL PROPERTIES OF MILD STEEL Description
Indian
Sell MA(lndlan)
British
American
Gennan
Japanese
IS-226
MA300HY
BS-
ASTMA36
DIN 17100
JIS-G-3101
CLASS-i
4360GR-43A Chemical Composition Carbon %
0.23-0.25
0.25
0.25
1.50
1.60
0.26
0.17- 0.20
......
Manganese
%
Phosphorus
%
0.06
0.055
0.05
0.04
0.05
Q.05
Sulphur
%
0.06
0.055
0.05
0.05
0.05
0.05
SIlicon
%
Mechanical Strength Tensile kgf/mm2
0.50 42-54
0.05
44.88-57.12 43.86-52.02 40.80-56.10 34.68-47.94
41-52
YIeld
kgf/mm2
26
30.60
26.01
25.50
23.97
24-25
Elongation
%
23
20
22
20-23
26
18-21
7
ANNEXURE II CHEMICAL COMPOsmON AND MECHANICAL PROPERTIES OF HIGH TENSILE STEEL Description
STANDARDS Indian
Specn. Nos.
British
American
IS-961 IS-85OO SAIL-MA SAIL-MA 1$-4360 ASTM EF-5AQ FE-490 350 MA-410 GR-50B A-441 HT
ASTM A-572 GR50
German
Japane..
DIN 17100 ST-52
JIS-G-3101 Class -3 Class-4
SS-5O
SS-55
Chemical
Carbon
%
0.20
Manganese %
Silicon
%
SUlphur
% 0.055
0.25
0.25
0.25
0.20
0.22
0.23
1.50
1.50
1.50
1.50
0.85 to 1.25
1.35
0.49
0.30
0.30
0.20
1.60
0.055
0.055
0.055
0.05
0.05
0.05
0.04
0.05
0.04
Phosphorus %
0.055
0.055
0.055
0.055
0.05
0.04
0.04
0.04
0.05
0.04
Mechanical Tensile kgf/mm2
58
49.98 to 62.22
49.98 to 62.22
55.08 to 67.32
49.98 to 63.24
49.47
45.70
49.98 to 61.26
52 to 62
55
YIeld kgf/mm2
36
34.68
35.70
41.82
36.21
35.19
35.20
35.19 to 36.21
28 to 29
40-41
Elongation
20
20
20
19
20
18
%
8
18 to 21 20 to 22 16to 19 14-17
)UJRE II
ANNEXURE III- (0) PROPERTIES OF EQUAL ANGLE SEcnONS AS PER IS:808 (PART V) - 1989 Size
t~
-'
101 loss -4
)..·55 ,)0
SeeHonal Unit Weight Centre of Area (em2) gravity (em) kg/m
0.04 J
l II
I, J7
(em)
(em)
Modulus of Sectlon(em~
4Ox4Ox3 4Ox4Ox4 4Ox4Ox5 4Ox4Ox6
2.34 3.07 3.78 4.47
1.80 2.40 3.00 3.50
1.08 1.12 1.16 1.20
3.40 4.50 5.40 6.30
1.21 1.21 1.20 1.19
0.77 0.77 0.77 0.71"
1.20 1.60 1.90 2.30
45x45x3 45x45x4 45x45x5 45x45x6
2.64 3.47 4.28 5.07
2.10 2.70 3.40 4.00
1.20 1.25 1.29 1.33
5.00 6.50 7.90 9.20
1.38 1.37 1.36 1.35
0.87 0.87 0.87 0.87
1.50 2.00 2.50 2.90
5Ox50x3 5Ox50x4 5Ox50x5 5Ox50x6
2.95 3.88 4.79 5.68
2.30 3.00 3.80 4.50
1.32 1.37 1.41 1.45
6.90 9.10 11.00 12.90
1.53 1.53 1.52 1.51
0.97 0.97 0.97 0.96'
1.90 2.50 3.10 3.60
55x55x4 55x55x5 55x55x6
4.26 5.27 6.26
3.30 4.10 4.90
1.51 1.53 1.57
11.00 14.70 17.30
1.67 1.67 1.66
1.06 1.06 1.06
2.96 3.70 4.40
6Ox6Ox4 6Ox6Ox5 6Ox60x6
4.71 5.75 6.84
3.70 4.50 5.40
1.60 1.65 1.69
15.80 19.20 22.60
1.83 1.82 1.82
1.18 1.16 1.15
3.58 4.40 ' 5.20
65x65x4 65x65x5 65x65x6 65x65x8
5.00 6.25 7.44 9.76
4.00 4.90 5.80 7.70
1.73 1.77 1.81 1.89
19.76 24.70 29.10 37.40
1.99 1.99 1.98 1.96
1.26 1.26 1.26 1.25
4.16 5.20 6.20 8.10
70x70x5 70x70x6 70x70x8
6.77 8.06 10.58
5.30 6.30 8.30
1.89 1.94 2.02
31.10 36.80 47.40
2.15 2.14 2.12
1.36 1.36 1.35
6.10 7.30 9.50
75x 75x5 75x 75x6 75x 75x 8
7.27 8.66 11.38
5.70 6.80 8.90
2.02 2.06 2.14
38.70 45.70 49.00
2.31 2.30 2.28
1.46 1.46 1.45
7.10 8.40 11.00
8Ox80x6 8Ox80x8 8Ox80xl0
9.29 12.21 15.05
7.30 9.60 11.80
2.18 2.27 2.34
56.00 72.50 87.70
2.46 2.44 2.41
1.56 1.55 1.55
9.60 12.60 15.50
9Ox90x6 9Ox9Ox7 9Ox9Ox8 9Ox9Ox 10
10.47 12.22 13.79 17.03
8.20 9.59 10.80 13.40
2.42 2.46 2.51 2.59
80.10 93.00 104.20 126.70
2.77 2.76 2.75 2.73
1.75 1.77 1.75 1.74
12.20 14.20 16.00 19.80
'''0
(It)4
Rxx (Rmed) Rw(Rmln)
(em)
Ixx-Ilr
9
>,.
ANNEXURE III-(a) Contd.. SIze
Ixx-I~ (em
SectIonal Unit Weight Cenlreof Area (em2) gravity kg/m (em)
Rxx(Rmed) Rvv(Rmln) Modulus of (em) Seetlon(em:s, (em)
100 x l00x6 l00x l00x 7 l00x l00x8 l00x l00x 10 l00x l00x 12
11.67 13.62 15.39 19.03 22.59
9.20 10.70 12.10 14.90 17.70
2.67 2.71 2.76 2.84 2.92
111.30 129.00 145.10 177.00 207.00
3.09 3.08 3.07 3.05 3.03
1.95 1.97 1.95 1.94 1.94
15.20 17.70 20.00 24.70 29.20
110 x 110x8 110x 110x 10 110 x 110x 12 110x 110x 16
17.08 21.12 25.08 32.76
13.40 16.60 19.70 25.70
3.00 3.09 3.17 3.32
196.80 240.20 281.30 357.30
3.40 3.37 3.35 3.30
2.18 2.16 2.15 2.14
24.60 30.40 35.90 46.50
12Oxl20x8 12Ox12Oxl0 120x 120x 12
18.70 23.20 27.50
14.70 18.20 21.60
3.23 3.31 3.40
255.00 313.00 368.00
3.69 3.67 3.65
2.37 2.36 2.35
29.10 36.00 42.70
130x 130x 10 130xl30x12
25.12 29.88
19.70 23.50
3.59 3.67'
405.30 476.40
4.02 3.99
2.57 2.56
43.10 51.00
150x 150x 10 150x 150x 12 150 x 150x 15 150 ~ 150 x 16' 150x 150x 18 150x 15Ox2O
29.21
22.90
34.77 43.00 45.65 51.00 56.21
27.30 33.80 35.80 40.10 44.10
4.08 4.16
635.50 746.30 898.00 958.90 1050.00 1155.50
2.98 2.97 2.93 2.94 2.92 2.93
58.00 68.80
4.25 4.31 4.37 4.46
4.66 4.63 4.57 4.58 4.54 4.53
98.70 109.70
180x 180x 15 180 x 180 x 18 180x 180x2O
52.10
40.90
4.98
61.90 68.30
48.60 53.70
5.10 5.18
1590.00 1870.00 2040.00
5.52 5.49 5.47
3.54 3.52 3.51
122.00 145.00 159.00
200 x 200 x 16 2oox200x2O 2OOx200x24
61.82 76.38 90.60 94.13
48.50 60;00
5.56 5.71
71.10
5.84 5.
2366.20 2875.00 3333.00
6.19 6.14 6.06 6.07
3.96 3.93 3.90 3.91
163.80 201.20 235.00 246.00
2OOx200x25
73.90
3470.02
10
83.50 89.70
ANNEXURE III-(b) PROPERTIES OF UNEQUAL ANGLE SEcnONS As per IS : 808 (Part V) - 1989
Size
Sectional Unit Wt. Centre of gravity Area kg/m eyy exx (em2)
Rxx Rvv (Rmed) (Rmln) Ixx
IYY (em4)
(em)
(em)
(em)
Modulus of Section zyy zxx
(em~
45x30x3
2.18
1.70
1.42
0.69
4.40
1.50
1.42
0.63
1.40
0.70
45x3Qx4
2.86
2.20
1.47
0.73
5.70
2.00
1.41
0.63
1.90
0.90
45x30x5
3.52
2.80
1.51
0.77
6.90
2.40
1.40
0.63
2.30
1.10
75x50x6
7.16
5.60
2.44
1.20
40.3
14.3
2.37
1'.07
8.00
3.80
8Ox6Ox6
8.65
6.80
2.87
1.39
70.6
25.2
2.86
1.28
11.5
5.50
100x 75x 8
13.36
10.50
3.10
1.87
131.6
63.3
3.14
1.59
19.1
11.20
11
ANNEXURE III-(e) PROPERTIES OF CHANNEL SECTIONS
SectIonal Unit Wt. Centre of
Iyy
Ixx
Rxx
Ryy
Modulus of SectIon
zxx
(em2)
kg/m
gravity eyy (em)
ISMC 75x4O
8.67
6.80
1.31
76.0
12.60
2.96
1.21
20.3
4.70
ISMC 100x50
11.70
9.60
1.53
186.70
25.90
4.00
1.49
37.3
7.50
ISMC 125x65
16.19
12.70
1.94
416.40
59.90
5.07
1.92
66.6
13.10
ISMC 150x 75
20.88
16.40
2.22
779.40
102.30
6.11
2.21
103.9
19.40
ISMC 175x75
24.38
19.10
2.20
1223.30
121.00
7.08
2.23
139.8
22.80
ISMC200x75
28.21
22.10
2.17
1819.3
140.40
8.03
2.23
181.9
26.30
ISMC 225 x 80
33.01
25.90
2.30
2694.6
187.20
9.03
2.38
239.5
32.80
ISMC250x80
38.76
30.40
2.30
3816.8
219.10
9.94
2.38
305.3
38.40
ISMC300x90
45.64
35.80
2.36
6362.6
310.80
11.81
2.61
424.2
46.80
Area
(cm~
(em~
(em)
(em)
K . A _
12
rrf
(em~
ANNEXUR!IV UNIT WEIGHT OF PLATES 1 mm thick plate weighs 7.85 kg/m2 Thickness In mm
Weight In kg/m2
Thickness In mm
Weight In kg/m2
7.85
23 24
180.55
25
·196.25
2 3
15.70 23.55
4
31.40
26
204.10
5
27
211.95
6 7 8
39.25 47.10
26
219.80
54.95 62.80
29
30
227.65 235.50
9
70.65
35
274.75
10
76.50
40
314.00
11
86.35
45
353.25
12
94.20
50
392.50
13
102.05
55
431.75
14
109.90
60
471.00
15
117.75
65
510.25
16
125.60
70
549.50
17
133.45
75
586.75
18
141.30
80
626.00
19
149.15
85
667.25
20
90
21
157.00 164.85
95
706.50 745.75
22
172.70
100
785.00
13
188.40
ANNEXURE V DIMENSIONS OF HEXAGON BOLTS FOR STEEL STRUCTURES All dimensions In mllllmetres.
x according to IS: 1369-1987 "Dimensions of screw thread runouts and undercuts·
z according to IS: 1368-1982 "Dimensions of ends of bolts and screws (first revlslon,SIze
M12
M16
M20
M24
d
Nom.
12
16
20
24
s
Nom.
19
24
30
36
e
Min.
20.88
26.17
32.95
39.55
k •
Nom.
8
10
13
15
1
1
15.2
19.2
24.4
·28.4
20
23
26
30
Max.
de b
Max
.14
:~"EV
ANNEXURE Vi ULnMATE STRENGTH OF BOLTS Bolts/Nuts conform to IS : 6639-1972 Mechanical Propertfes conform to IS: 1367 (FOR PROPERTY CLASS 4.6/4) Ultimate shearing stress = 2220 kgf/cm2 Ultimate bearing stress = 4440 kgf/cm2
BoItdla (mm)
Shearing strength for one bolt
Bearing strength (kgf) for one bolt for member thlckM."
Single shear(kgf)
Double shear(kgf)
3mm
4mm
Smm
6mm
7mm
12mm
2511
5022
1598
2132
3197
3730
16mm
4464
8928
2131
2842
4263
4973
20mm
6974
13948
2664
5328
6216
24mm
10043
20086
3197
3552 4263
2664 3552 4440 5328
6394
7460
(FOR PROPERTY CLASS S.6/S) Ultfmate shearing stress= 3161 kgf/cm2 = 3160 Ultimate bearing stress = 6322 kgf/cm2
Boltdla (mm)
Shearing strength for one bolt Single shear(kgt)
Double shear(kgt)
Bearing strength (kgf) for one boH for member thlckn... 3mm
4mm
Smm
6mm
7mm
12mm
3575
7150.
2276
3035
3793
4552
5311
16mm
6356
12712
3035
4046
5058
6070
7081
20mm
9931
19862
3793
5058
6322
7587
8851
24mm
14300
28600
4552
6070
7587
9104
10621
Note: The above bearing values are against the bolt surface only. Bearing values against the member surface shall be determined based on bearing strengths of materials used.
15
ANNEXURE VII PROPERTIES OF ANCHOR BOLTS METRIC SCREW THREADS AS PER IS: 4218 (PA~·3)·1976 WITH ISO
(Ultimate Tensile Stress =19.8 kgf/mm2)
Sr.No.
Nominal PHchof Diameter (mm) Threads (mm)
1. 2.
20
3.
22
4. 5. 6. 7.
16
24 30
32 40
8.
45
9.
50
10. 11.
56 62
12.
75
13.
80
2 2 2.5 2 2.5 2 3 2 3 2 2 3 2 3 2 3 2 3 4 2 3 4 2 3 4 2 3 4
Tensile Stress Areo (mm2)
157 258 245 318 303 384
353 621 581 713 1140
1085 1460 1400 1820 1750 2300 2220 2140 2830 2760 2670 4320 4210 4100 4790 4680 4570
UIHmate Tensile strength (kgf)
3109 5108 4851 6296 5994 7603 6989 12296 11504
15305 22572 21483 28908 27720 36036 34650 45540
43956 42372 56034
54648 52866 85536 83358 81000 94842 92664
90486
(
c TI C ~
V {t
:'1
I.
l/.: V'., IIIE
16
APPENDIX-I
QUALITY ASSURANCE PLAN I. INTRODUCTION A well-planned and executed Quality Assurance Programme Is necessary to ensure. delivery of acceptable material In a timely manner. The objective of the programme Is to establish thot transmission material Is In conformance with the specifications of the purchase contract. thIs programme must be established In a manner that provides open avenues of communication throughout the plant. It Is headed by a Manager having overall authority and responslbllHy to establish, review, maintain and enforce the programme; II. QUALITY OBJECTIVE - To develop and lay down the procedlJres followed In general for qualify control. In the organisation. - To create confidence In the customers about the quality of the towers supplied. - To create awareness In vendors about the system of control on quality of the goods supplied.
III. QUALITY POLICY The design of towers should fully meet the customers' quality requirements Including functional, safety and life characteristic with adequate attention to economy. Specifications anclplant standards are strictly adhered to during manufacture.
,
There Is a scientific sales development and evaluation of vendors.
IV. ORGANISATION OF QUALITY CONTROL DEPARTMENT Quality Control Department Is autonomous by way of reporting directly to highest authority In the organisation. The decision of Quality Control Department remains final which will be within the limits of specified standards. . There exists an Inbullt orientation and rotation system among personnel In ~l.Jality ContrQI Department which gives opportunity to all persons In the department to leam all the aspects of quality control.
V. QUALITY PLANNING The objective of Quality Planning Is to Include the procedures for mat~lrig arrangements to manoge the contract requirements. The various functions are as follows: V.l. Preparation, Issue and updating of Quality Assurance Manual.
V.2. Preparation, Issue and updqtlng of Inspection Instructions and formats for all stages. V.3. Developing schemes and sampling plans based on standard quality control technlque.s for the Bought-out-Items and the Items fabricated In the Plant. 17
VA. To develop Vendors along with Procurement Department and from time to time guide them In fulfilling technical requirements and prepare schemes for Ve.ndor evaluatlon'by Procurement Department.
V.5. Periodic calibration of measuring Instruments and gauges.
V.6. Vendor Performance Evaluation Is made by Material Management based on feed back from Quality Control.,Department. The Incoming materials are subjected to Inspection at the site as well as In,the WorKS: I'
. ~ i-,
The accepted materials are sent for further processing/despatch and rejected materlal~ are sent back·tathe supplier. Care Is taken that there Is no mix up of rejected lot with the one which Is accepted. The evaluation of vendor performance Is done by Material Management Department wlttHeed back on other factors like DeliverySchedules, Competitiveness and Reliability of Supplies. V.7.,'!~~PQrtlng by Q~allty Control Department Is completely standardized by way of developing formats as can be-seen from formats Included In this manual.
VI. DESIGN AND DRAWINGS VI.l.: The Customer's quality requirements are translated by Design Department Into achievable Specifications and the same are Improved continuously. The Customer's Specifications are studied and considering all factors, towers are designed.
VI.2. Based on results of test tower, Improvements In designs, If required, are carried out.lmprovements In design are also done based on Information from Construction Division and Cllent~.
VI.3. To achieve economic specifications, the towers are designed for the minimum weight per tower meeting the funcftonal requirements.
VIA. The Drawings and Bills of Materials are circulated to all concerned. The modifications In drawings. and communication of changes required are done promptly.
VI.5. Design Department helps shop floor In critical and Important activities and also In simplifying the methods of manufacture.
. ,.
VII: COMPANY STANDARDS
Q
VII.l. Towers are designed. manufactured. erected and commissioned In accordance with the relevant National/International Standards Or Customer Specifications.
X
,1
VlI.2. For the aspects not covered by National/International/Customer Specifications. the CompalY/Plant Standards are followed.
In
VlI.3. All National Standards. and International Standards are available In Quality Control Department. The extracts/Information applicable to various Departments are Issued from time to time for their reference and Implementation.
"
VIII. CONTROL ON INSPECTION-EQUIPMENTS/TOOLS/GAUGES VIII.l. Verniers, micrometers, GO and NQ-GO-Gauges and Magnetic Coating Thickness Gauges are calibrated periodically and records are maintained. 18
'.,
.
"
VIII.2. Measuring Scales and Metallic Tapes are Inspected on receipt with standard ones by comparison .and sent to user department only When found acceptable.
I)
VlII.3. Templates and Bend Gauges and Component Sketches are obtained from original source I.e. Template Shop. Template Shop finalises these based on actual assembly of proto1yp.e of e.och structure. VlII.4. Testing equlpments like Universal Testing Machine In laboratory are calibrated periodically by recognised Inspection Agencies. "
.....
IX. MATERIAL MANAGEMENT IX.l. The list of registered approved vendors maintained Item-wise Is updated. penodl.callY based -I' on evaluation of performance of existing vendors as well as newly approved ones,: . IX.2. Performance of the vendors (QCD) Is closely followed through the feedback received from Stores and Quality Control Department. Sustained efforts are put by Q.~D. Improve the vendors.
g
to
IX.3. Acceptable materials are seggregated and sent for further processing/packing/despatch.
e (
IX.4. Rejected materials are seggregated-stored In separate bins/areas and vendors are Intimated about rejections and the materials are returned for replacements.
• IX.S. Vendor Development And Evaluation
IX.S. J. Registration of Vendors Is done based on the following steps:
In
(I) Getting. complete Information on a prescribed ~uestlonnalre. (II) Inspection by Q.C. Representative of the factory premises for verification of Manufacturfng & Testing facilities. (III) Sample testing and performance of trial orders.
IX.S.2. EXisting Registered Vendors are rated based on the factors like qualify, price, delivery and their service regarding the consignments supplied. . IX.S.3. Improvement In performance of vendors Is done by continuous technical guidance by Q.C. and Design Department. . X. INCOMING MATERIAL INSPECTION
''''
The Incoming material Is purchased as per deta!led Specification and drawings referred to In Indent by Scheduling Section or as per details flJrnlshed by Designs (Engineering) DMslon. The Incoming material can be broadly classified In the following categories:
'01
X.l. Raw Materials
X. J. J. Structural Steel (a) Quality of Steel-Generally conforms to IS: 226-1975 designation Fe-410-S, BS: 4360 Grade SOB or any other equivalent specification stipulated In the Contract.
19
(b) Physical Properties:
(I) Verification of Mill Test Certificate. .(11) Actual Test Certificates from Laboratory. (0) _pIIng Plan for Dimensional and Visual Inspection-single sampling plan as per IS:2500 (Part-I)-1973. Inspection Level -IV. Acce'ptabllltyQudll1y Level -1.5 (d) . V*.IaiDefectt- Scaling (Burnt Surface) Lamiriation (Folds) Heel Ground C~a~~.
Plpy. R()ugh Surface Scab (e) Dimension defects as per 15:808-1989 115:1852-1985 Leg-Length (Flange) below or above tolerance. out of Square Camber Weight per metre below or above tolerance. (1)' 'Chemical Analysis: Mill test certificates for each lot are verified and conformatory tests on about four samples per month from the major Purchasers are analysed as per IS:226 or the other applicable standard. (g) ,Document: , Inspection Report of Steel (QCD-n.
X. 1.2. Zinc (a) Quall1y:IS:209;'1979-Grade 99 .95% and IS:4699~1984 Grade 98.50%. (b) Sampling: One sample per lot for chemical analysis. If one sample falls then two more samples are analysed (as per IS : 209) for final decision. (c) [)O(;\Jment: Te.st Certificate from Laboratory. X.2. Bought-out Items
X2. I. :Fasteners (a) Bolts ond Nuts: (I) Bolts: Product speclflcation-lS:6639-1972 Technical Supply Condltlons- IS: 1367. (II) Nuts: Product speclflcations-lS:1363-1984 Technical Supply Condltlons-IS:1367. (III) Sampling: IS:2614-1969. (Iv) Document: Inspection report of Bolts/Nuts (QCD-2). (b) Spring Washers: (I) Specifications: 15:3063-1972 (II) Sampling: 15:6821-1973. . (III) Documents: Inspection Report of Spring Washers (QCD-3).
X.2.2. Towel Accewrles
0) Materlal-I5:226-1975--Designo1ton FE-41 (}S(St-42-S) and of specified category as per BS : 970. 20
'.
(II) Manufacture-As per Drawing. all) Sampling Specifications: IS:25OO (Part-1)-1973 Inspection Level-IV AQL--1.5. Ov) Documents-Inspection Report for Accessories (QCD-4). X.3. Identification for all Incoming material X.3.1. Accepted Lot-No paint X.3.2. Rejected materlal-Red paint XI. PRE-PRODUCTION
Pre-production Is done for each structure/tower for finalising the Individual member Otem)sketches which are used for mass fabrication. This Is done In the following way. Xl.l. The draft sketches are made based on computerised approved structural assembly drawings. X1.2. As per the draft sketches, pieces required for one model assembly are fabricated and assembly of one model Is done on ground horizontally. Revisions and additions required as per the model assembly are Incorporated In the draft sketches. XI.3. Wherever required the structure assembled as above Is also tested for the specified loads and modifications required, If any, are Incorporated In the draft sketches. XIA. After Incorporating all revisions In draft sketches, the same are flnallsedandtradngs are made. The copies of these final sketches are sent to Scheduling, Production, Qudllty Control ;ond Inspection Departments to use for mass fabrication. XI.S. If any revisions are required In sketches at a later date, the same are Incorporated In the original tracing and copies are promptly forwarded,to all concemed. '
XI.6. At the time of pre-production, the bend gauges and templates are also prepared. Due to revisions, If required, new/revised Templates/Bend Gauges are prepared and ,aU old ones 'are destroyed. XII. IN-PROCESS INSPEcnON
•
XlI.l. Inspection of Fabrication XII. 1. 1. The raw material accepted by Quality Control and Inspection Department Is Issued to the fabrication shops by Raw Yard Department on the Instructions of ,Planning and Schedunng Department. The fabrication shops verify the correctness of material before accepting for mass fabrication.
XII. 1.2. Structural members (Items) are fabricated as per the final sketch. The fdbrlcatlon Is done In accordance with IS:802 (part 2-1978), IS:7215-1974 and Plant Standards. XII. 1.3. In-process Inspection during fabrication Is done by checking the first piece thoroughly as per the sketch, IS:802 (Part-2-1978), IS:7215-1974 -and Plant Standards. The clearance for mass fabrication Is given only after the first piece Is found acceptable.' Regular Inspection Is also carried out by periodically Inspecting pieces during the time the lot Is under fabrication, which ensures maintaining correct quality throughout fabrication of the lot. 21
.XII. r.4. The complete fabricated lot Is taken for final Inspection before galvanising. Final Inspection of fabricated lot Is done as per the following procedure:XII. 1.4. 1. Initially, the verification of stamping of member (Item No.) and Quantity (total number of .pieces In the lot) Is done with resPect to the Route Sheet. XII. 1.4.2. One piece from the lot Is drawn at random and detailed Inspection Is done as per sketch, 15:802 (Part-2-1978), IS:7215-1974 and Plant Standards wherein the following parameters are checked:-
(I) (II) (III) ov) (v)
Section & SIte: Angle section & gusset thickness. Straightness-Comber-VIsual method or thread method. squarne,srBy Trl-square; Size of holes-by GO and NO GO gauges. . Dimensional checking: (a) . Length of member and overall size of gusset. (b) Hole posltlons-back mark and spacing. (c) End Securlty-Cut-edge security and rolled-edge security. (d) Skew Cuts-Flange cuts, corner cut etc. (e) Bend-Posltlon of bend and degree of bend by Bend Gauges. (f) Chlpplng-Length and depth of chipping by Chipping Gauges. (vi) Visual Inspection: (a) Raw material roiling defects. (b) Punch ~nd die marks. (6) Burrs due cropping, punching etc. (d>,. ..~~,Jrfa9~.qefects-rough surface cjue to scaling, thickness reduction due to bend. (vii) Ch~cldng.With·Ghecklng cleat-The I eg member Joints, lattice Joints and cover cleats ·;ar~\:·~b~keQ\,Wtth'Checklng Cleats', made exactly as per the corresponding fitting members. (viII) Gussets are checked with gusset templates, correctness of which Is first verified. Criticality of 'SEr ,(If. arw) Is ensured during gusset Inspection. OX) ( Welded Items like footings are also Inspected for welding test visual characteristics of weld, dimensions checking of weld by means of gauges and dye penetration test wherever required. Xli. 7.4.3. (a) Once. the Inspection of·flrst piece Is over and It Is found acceptable, It Is treated as templa:te (or master piece) and Inspection of other pieces In the lot Is done by vlsVSJI comparison method with respect to this template. Joints of legs, Joints of lattices and cover cleats are checked with checking cleats. Gussets are checked with gusset templates. During Inspection by visual comparison whenever a deviation Is noticed In any piece, It Is checked In detail In the same way as the first piece. Pieces found defective In the. lot are rejected. (b) In case the first piece drawn from the lot Is not acceptable, additional samples are . :drown as perIS:2500 (Part-1-1973) Inspection level I and these pieces are Inspected as per XII.1.4.2. Even If on~ piece out of these Is found unacceptable, the lot Is finally rejected. If all these pieces are found acceptable the Inspection of lot Is done as stipulated above In XII.1.4.3 (a).
to
22
)
c ~
1 st
XII. 1.5. Rejections ~,. The defective pieces found In a lot after Inspection as per !.1.4 are rejected. The rejections are classified In the following two categories: XI/.1.5. 1. Rectifiable ReJection: These cover the defective pieces having defects which can be or permitted to be rectified. SUch defects which are rectifiable are given code numbers. which are Indicated In the Rectifiable Rejection Slips prepared for each rejected" piece. The referred pieces after rectification are Inspected Individually. XI/.1.5.2. Out RIght RejectIon The defective pieces whlch-cannot be rectified are rejected out-right and are Scrapped.
XII. 1.6. Documentation 0) Inspection & Loading Report (II) Rejection Slips - (a) Rectifiable (b) Out-Right 011) Weekly Inspec~on Reports. a~ XII. 1.6. 1. (a) Dally Inspection and Loading Reports : forwarded to Senior Manager (Prodn.) Galvanising Department, Stores & Accounts Department. (b) Rectifiable rejection slips are sent to Senior Foreman of Fabrication shops along with the material. (c) Out-right Rejection Slips are sent to Senior Manager (Production) and Planning & Scheduling Department. (d) Weekly Inspection Reports are forwarded to Divisional Manager (Prodn.) and Divisional Manager (Designs). XII. 1.6.2. The defect analysis Is done by Sr. Manager (Prodn) & Divisional Manager (Prodn) and corrective measures are taken to avoid recurrence of those defects In future. XII. 1.1. Identlflcatlon:-The pieces rejected out-right are applied red paint and sent to scrap bin. The pieces for rectification are marked with rectification required and retumed to corresponding shop along with 'Rectifiable Rejection Slip.'
XII.2. Inspection of Galvanising 5peclflcatlon~:
15:2629-1985 Practice for Hot Dip Galvanising or Equivalent like ASTM:A-123 and
85: 729. XlI.2.1. Surface Preparation-Chemicals: XII.2.1.1 Degreaslng Solution: To remove contamination by 011, grease and paint etc. material Is dipped Into caustic soda solution which Is' kept at a temperature between «PC and 80°C. The strength of solution Is 4% to 10% I.e. 40 g/Iltre to 100 g/Iltre. The strength of solution In degreaslng tank Is checked every week. Altematlvely cold degreaslng with actlvaled caustic soda can al.so be used. Immediately after degreaslng the material Is rinsed In running water before pickling. 23
XII.2. 1.2. Pickling Solution: Dilute Hydrochloric Acid (HCl) having Acid strength of 4% to 18% (40 gIl. to 180 g/t) and specific gravity of 10-27° Be Is used for pickling the material. The soiution is maintained at room temperature. The desired strength and °Be specifiC gravity Is checked In the beginning of each shift and. If required fresh concentrated acid Is aded. Mild agitation of material In pickling tank is done to reduce pickling tlme.A1ternatively dilute Suiphurlc Acid (H2S04) having Acid strength of 4% to 15% (40g/l to 150 gil) and specific gravity of 11-28° Be Is also used for pickling 1he'moterlal. I XII.2.1:3. Rinsing: After pickling the material Is rinsed In running water. XII.2.1.4. Pre-fluxing Solution: The rinsed materia! after pickling Is Immersed In prefluxlng solution (ZInc Chloride and Ammonium Chloride). The strength of pre-fluxing solution Is maintained between 160 g/iitre to 300 g/lltre at room temperature. The iron content In the solution Is not allowed to exceed S""g/lltre. The"prefiuxlng solution Is checked for strength In the beginning of each shift and for Iron content once a week. XII.2. 1.5. Documentation: (I) Weekly records of shlf1wlse acid strength. (II) Galvanising process Inspection Report.
XII.2.2. Dipping XII.2.2. I. Quality of Zinc: Zinc conforming to Grade Zn 98.5 of IS:4699-1984 and Grade Zn 99.95 of IS:209-1979 Is used forthe purpose of galvanising.
XII.2.2.2. Bath Temperature: The temperature of molten zinc In the main as well as au~lIIary baths for bolts, nuts and accessories Is consistently maintained" between 450°C to 465°C. The temperature Is ch~ked regularly In the shift to maintain It within specified limits. There is automatic control and recording of temperature of molten zinc In kettle. XII.2.2.3. Flux blanket: A layer of flux blanket of Ammonium Chloride ( NH4CI) is maintained on 1he t9P layer of molten zinc In the bath. XII.2.2.4. The other requirements like Aluminium addition, reduction In suspended dross, high rote of~rperslon, low speed of withdrawal are maintained In such a way that quality of galvanlsed product Is consistent. " XII.2.2.5:-Documents: Galvanising Inspection Report.
XlI.2.3. AIIer"dipplng treatments XII.2.3. 1. Centrifuging: Small Items, fasteners and hardware fittings galvanlsed In baskets are centrifuged to remove excessive zinc Immediately after dipping and before water quenching. XII,~.J. ~..
"Water Quenching: After withdrawal from molten zinc the material Is quenched Immedlqtely In water. The w.ater 10nk Is cleaned every fortnight to prevent accumUlation of corrosivesOlts:
XII. 2. 3. 3. Surface Passivation by Quench Chromatlng: To protect the galvanlsed surface from wet storage staining and to avert attack by corrosive marine conditions the material Is quenched In" 24
gIl.
solution of sodium dichromate. The strength of solution Is maintained be1ween 0.12% and 0.15% and checked by colour comparison regularly. XII. 2. 3.4. Documents: Weekly records of shlftwlse acid strengths.
XIII. INSPECTION AND TESTING OF FINISHED (GALVANISED) MATERIAL XIII. I. Visual Inspection Regular Inspection of each lot Is carried out In accordance with IS: 2629-1985, ASTM : A-123 and BS: 729 to ensure that zinc coating' Is uniform, adherent, reasonably smooth and free from such Imperfection as flux, ash and.bare patches, black spots, pimples, bulky-white deposits and blisters; The material not conformng to visual characteristics Is rejected.
on L .•
+" nd
Documentation:
(I) Galvanising Inspection Report. (II) Store Receipt Notes.
XIII.2. Uniformity of Coating (Preece Test) To test for uniformity of zinc coating thickness and to determine thinnest spot of zinc coating the copper sulphate solution test Is carned out In accordance with IS:2633-1986 and ASTM : A-239. The samples are subjected to four dips of one minute each, which they should withstand satisfactorily I.e .. they do not show any red deposit of copper upon base metal. or
This test Is applicable only for small articles and therefore for material of big and Inconvenient size, unlnformlty of coating Is determlnd with Magnetic Thickness Gauge after taking 5 readings at each end and In the middle of the piece.
t. ..
)" ic
XIII.2.1. Documentation: Galvanising Inspection Report. XIII.3. Weight of Zinc Coating Speclflcatlons-IS:4759-1984, ASTM : A-123 and BS : 729.
lb
XIII.3.1. Thickness of Zinc Coating by Magn$lc Gauge. L
XIfI.3. 1. 1. No. of samples:
lei
e
3 for tower materials per shift. 1 for accessories per shift.
XII/.3. 1.2. Minimum Zinc Coating (I) Tower Material (a) 5 mm thick and over-86 microns. (b) Under 5 mm but over 2 mm thlck-65 microns. (II) Hardware fittings, bolts, nuts and tower accessories - Minimum 43 microns as per IS :1367 (Part 13-1983).
XlII.3.2 Weight of zinc coating by Hydrogen Evolution Apparatus: d \
XII/.3.2.1. No. of samples: 2 for tower material per shift.
).
XII/.3.2.2. Minimum Zinc Coating: (I) Tower Material:
(a) 5 mm thick and over-610 g/sq.m. (b) Under 5 mm but over 2 mm thick - 460 g/sq.m.
25
(II) Hardware fitting, bolt, nuts and Tower Accessories - Minimum 300 g/sq.m. as per 15-1367-(Part 13)-1983.
XIII.3.3. Documents: Galvanising Inspection Report. XlnA. Adhesion of Zinc Coating Specifications - IS : 2629-1985, ASTM : A-123 & BS : 729 XIII.4.1. Pivoted Hammer Test for Tower Members. XlII.4.2. Knife test for Hardware FIttings, Bolts Nuts and Tower Accessories. XIII.4.3. Two standard blows by hammer forming paraliellmpresslon (with 6 mm spacing) and prying with stout knife should not peel/flake off coating. XIII.S The material Inspected _qnd tested as per above reqUirements when found acceptable Is released by Q.C.D. to finish yard for storage, packing and despatch. XIV. STORAGE, PACKAGING AND PACKING XIV. I. The material Is dipped In dlchromatlng solution to protect from white rust formation. XIV.2. The components are bundled In pre-determined method depending upon customers' requirement/mode of transport. XlV.3. For export orders, Itemwlse bundles to the extent of 1 tonne to 1.5 tonnes are made by passing 8 SWG or 14 SWG wires In holes at both ends of the member and also strapping the bundles at distance of 1.0/1.5 metres with electro galvanlsed steel straps. The strapping Is done by means of strapping machine. XIV.4. The Indigenous orders are dealt with differently. The bundles are Itemwlse but the weight Is restricted to 100 kgs. to facilitate manual loading/unloading. The process of bundling Is same except strapping' which Is eliminated. XIV.S. Small articles and accessories are packed In double gunny bags/wooden boxes. The boxes are strapped In addition to nailing. Weight of material boxes ranges between 500 kg to 1500 kg. Boxes are made In accordance with drawing as per Company Standards. XIV.6. Each package/bundle Is prepared only after scrutiny of Individual component by Its Identification mark. StenCiling of Item number on the top of bundle/package also Is done.
• XIV.7. The bundles/packages are also stencilled with Identification mark/shipping mark etc. 't
26
A. SAMPLING PLAN FOR INCOMING MATERIAL a. I.
Lot Size No. of Pes
Sample Size
Acceptance Number
2to8 9-15 16-25 26-SO 5i-l00 101-lSO 151-500
2 3 5 8 8 32
0 0
S01-1,OOO
80 125
( ;
~.
,
bv n~s ,
....
'
k ...
<('t Its
Sections, Accessories and Bought-out Items. Sampling Specifications : IS:2500 (Part 1)-1973 Inspection level IV, AQl-1.5
1,00 1-3,000 3,001-10,000 10,001-35,000 35,00 1-1 ,SO,OOO 1,50,001-5,00,000 5,00,001 and above II. III. IV. V.
Rejection Number-
a a 0 1 2 3 5 7 10 14 21 21
so
200 315 500 800 800
1
2 3 4 6 8
11 15
22 22
Fastener Sampling as per 15:2614-1969. Spring Washer and non-threaded fastener sampling as per 15:6821-1973 Zinc Sampling as per 15:209-1979 Sampling, for any other Incoming material whose relevant speCifications does not mention any specific sampling plan should be done as per I above.
-Depending upon the nature of defect, availability of material and contractual commitment fully rejected lots may be subjected to 100% Inspection and only such quantity which meets the quality reqUirements of relevant specifications, should be accepted.
27
b. SAMPUNG PLAN FOR PHYSICAL PROPERTIES OF BOLTS. NUTS. SPRING WASHERS AS PER IS-26141969 AND IS: 6821-1973 Sample Size
Lot Size
upto
1,(0)
5
1,001 TO
3,(0)
8
3,001 TO
10,(X)J
13
10,001 TO 35,(X)J
20
35,(0)
32
Over
Acceptance Number
o o o o
c. SAMPUNG PLAN FOR GALVANISING TEST FOR THREADED FASTENERS AS PER IS-1367 (PART-13)-1983 AND HARDWARE FITTINGS
Sample Sizes
Lot Size Upto and Including
500
3
50 1 Upto and ·Including
35,(0)
5
Over
35,(0)
8
Microscopic test on Electroplated Spring Washers per lot
2
1 ± j,
'c
.. ~
01
1.1
.1' I.,.,
nc
~. '
I
28
QUAUlY CONTROlOEPARTMENT
DATE: d. QCD-1
-----
INSPEcnON REPORT OF STEEL STACKING/PREUMINARY
I
SECTION:
1. Supplier _________________ 6. Location _______________ 2. Quality of Steel ______________ 7. Stacking started on __________ 3. P.O. No. _________________ 8. Stacking completed on _____. ___ 4. Tonnage _________ 9. Test Cert. No. _____________ 5. G.R. Note No. _____________ _ 0_ _ _ _ _ _ _
1.
_ _ _ _
IMPORTANT INTSTRUCTIONS
1.1 The tolerance on leg length shall be as follows as per IS : 1852-1985.
Leg Length
Tolerance
I
Overmm 45 100
Upto & Including (mm) 45 100
± 1.5mm ±2 mm ±2 per cent
1.2 In the case of unequal angle: 45 x 30 mm, the tolerance on longer leg length shall be +2.0 mm -1.5mm. 1.3 Out of Square - The legs of angles shall be perpendicular to each other within a tolerance of ± 1 degree. 1.4 The difference between the leg lengths of equal angles shall be limited to 75 per cent of the totartolerance (plus and minus) specified on the leg lengths. •1.5 Weight: The tolerance on weight per metre shall be ±5% In the case of angles 3 mm In thickness and +5/-3% In the case of angles over 3 mm In thickness. 1.6 All finished steel shall be well and cleanly rolled to the specified dimensions, sections and weight. The finished material shall be free from cracks, surface flaws, lamination, rough, Jagged Imperfect edges, scaling (excessive burnt surface) plpy cross section, ground heel and all other harmful defects. SAMPLING SPECIFICATION:
IS 2500 (1)- 1973, Inspection level-IV, AQL-1.5 or 100% Inspection of Steel carried out.
2. VISUAL INSPECTION 2.1 Lot Size ________________ 2.2 Sample Size _____________ _ 2.3 Acceptance No. ___________ 2.4 Rejection No. _____________ _ 2.5 No. of Deffectlves found _ _ _ _ _ _ _ _ REMARKS: LOT ACCEPTED/REJECTED·
29
3. DIMENSIONAL CHECKING
3.1 lot Size _________________________ 3.2 Sample Size _______________________ 3.3 Acceptance No. _____________________ 3.4 Rejection No. ________________________ 3.5 No. of defectives found ___________________
-
- - - __-
-
-
-
-
-
-
-
-
REMARK: LOT ACCEPTED/REJECTED-
REMARK: LOT ACCEPTED/REJECTED3.6 Actual Dimensions
Sr. No. 1. 2. 3. 4. 5. 6. 7. B. 9. 10.
Lea Lenath
Thickness
Sr. No. 3l. 32. 33. 34. 35. 36. 37. 3B,.'
39. 40. 4l. 42. 43. M. 45.
11. 12. 13. 14. 15. 16.
46.
17. " lB. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. , 29.
47. 48. 49. 50. 5l. 52.
30
60
53. 54.
55. 56. 57. 58. 59.
Additional Sheets may be used If there are more number of pieces.
30
Lea Lenath
Thickness
,
REJECTIONS Out of Square
ISS
Scaling
Heel Grd.
Unequal Section
Hair Une Crack
Roiling Defect
Pitted"
Plpy
Mat. Def.
Others . Total ReJ. Qty.
*Dependlng upon the nature of defect, availability of material and contractual commitments, fully rejected lot may be subjected to 100% Inspection and only such quantity which meets the quality requirements of relevant specifications shall be accepted. In such case, the actual dimensIons of ~ rejected angles only may be given In 3.6. SI.I.~
4. PHYSICAL TESTING 4.1 Lot Size ______________________________________ _ 4.2 Sample Size ___________________________ :.. _________ " 4.3 Acceptance No. _________________________________ _ 4.4 No of defectives found ________________________________ " 4.5 Retest Samples ________________________________ :... __ 4.6 Acceptance No. _________________________________ _ 4.7 No. of Defectives found _____________________ "__________ . 5 FINAL REMARKS: LOT ACCEPTED/REJECTED 5.1 1000/. INSPECTION FINAL REMARKS: Total No. of pieces Accepted: _____ (Refer 2.5 and 3.5) Total No. of ple~es ReJected: _____ ._ (Refer 2.5 and 3.5)
Assn. OFFICER/INSPECTOR
SR. ENGINEER (INSPN.)
31
QUAlITY CONTROL DEPARTMENT DATE: _ _ _ __
•• BEND TEST SUPPU~
P.O. NO.
SECTION
QUAN:JI1Y
Ir
(Tomes)
NO. OF TEST pcs. I.D.MARK BEND DEGREE FORM~~
18(f
180°
0
180
It
180
OIA fOR
1-
t~
aENl? IN rnr.n (3 TIMes
THICKNESS)
o
REMARkS
~ 1~ UI VII
ASSn. OFFICER/INSPECTOR
SR. ENGINEER (lNSPN.)
32
1/:
f. REPORT ON TEsnNG OF PHYSICAL PROPERTIES No.:
I
l'
MATERIAL , MATERIAL UST NO. W.O./P.O. NO. , SUPPUER/CUENT , TENSILE TEST
:::::-
SPECIACATIONS QUANTITY DATE OF TESTING STAMPED AS
::::-
~
I I
1YPE AND SIZE
1
IDENTlACATION MARK
~
WlDTH/DIA (mm)
I I
THICKNFSS (mm)
I
GAUGE LENGTH = 5.65 vA (mm)
AREA 'A' (mm2)
1
RNAL GAUGE LENGTH (mm)
J
YIELD LOAD (kgf) ULTIMATE LOAD (kgf) YIELD STRESS (kgf/mm2) U.T.S. (kgf/mm2) PERCENTAGE ELONGATION FRACTURE
BEND TEST FORMER DIA. (mm)
.
BEND AT 180° (FORMER DIA. --mm) RNAL REMARKS :-
t
Test Conduced By:
Test Witnessed by:
,
33
A.
QUAUlY CONTROL DEPARTMENT
DATE:
-----
QCD-2
g. INSPECTION REPORT FOR BOLTS/NUTS Description of the Material: ______________________________ Material Specification : 15:6639-1972/15: 1363-1984/15: 1367-(PI 3)-1979. Purchase Order No. _____________ G.R. Note No. ______________ SUpplier _______________________________________ W.O. ___________________ Black/Galvd. Date of Receipt ______________ Date of Inspection ____________
_ _ _ _
--------------------------------------------
SAMPLING SPECIFICATION: 15:2614-1969.
1. VISUAL INSPECTION 1.1 Description of the material _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1.2 Lot SJze _________________ 1.3 Sample Size _____________ _ 1.4 Acceptance No. _________ '___ 1.5 Rejection No. _____________ _ 1.6 No. of Defectives found ____" :.. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ 1.7 REMARK: LOT - CONFORMS/DOES NOT CONFORM to Specifications. 2. DIMENSIONAL CHECKING 2.1 De~rlptlon of the material _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2.2 Lot Size _________________ 2.3 Sample Size ___________ "' _ 2.4 Acceptance No. ____________ 2.5 Rejection No. ___________ .. __ 2.6 No. of Defectives found ______________________________ _ 2.7 REMARKS: LOT - CONFORMS/DOES NOT CONFORM to Specifications.
2.S Actual Dimensions of Bolts (15:6639-1972) 2.S.1 2.S.2 2.S.3 2.S.4
Description Dla of Bolts Shank dla Major dla Total length
2.S.5 Thread length
2.S.6 Pitch 2.S.7" Width across flats 2.S.S Width across corners 2.S.9 Thickness 2.S.10 Tolerance Class
Required dimensions In mm 12/16 11.30-12.70/15.30-16.70 11.541-11.966/15.512-15.962 Upto 30: ±1.05 35 to 5O:± 1.25 55 to SO: ± 1.50 22: +3 -0 25: +3 -0 1.75/2.0 lS.4S-19.0/23.16-24.0 Min. 20.SS/Mln. 26.17 7.55-S.45{9.55-1 0.45 Sg
'lA
Actual dimensions In mm
. 2.9 Actual Dimensions of Nuts (IS: 1363-1984) Description 2.9.1 Width across flats 2.9.2 Width across comers 2.9.3 Thickness 2.9.4 Pitch 2.9.5 Tolerance Class
Required dimensions In mm 18.48-19.0/23.16-24.0 Min. 20.88/Mln. 26.17 9.55-10.45/12.45-13.55
Actual dimensions In mm
1.75/2.0 7H
REMARKS:- The Nut threads shall be oversized by 0.4 mm for M16 Nuts and 0.3 mm for M12 Nuts as dlametral allowance for galvanising on male threads. Nuts should be oiled after ratapplng. 3. PHYSICAL TEST: (a) Bolts to property class 4.6 as per IS:1367 (Part-3)-1979. (b) Nuts to property class 4 as per 15:1367. . 3.1 Description of the material _ _ _ _ _ _ _ _ _ _ .:.. _ _ _ _ _ _ _ _ _ _ _ '._ _ _ _ _ _ _ _ 3.2 Lot Size _________________ 3.3 Sample Size _____ !.. _ _ _ _ _ _ _ _ 3.4 Acceptance No. ____________ 3.5 Rejection No. _____________ _ 3.6 No. of Defectives found ______________________________ _ 3.7 REMARK: LOT - CONFORMS/DOES NOT CONFORM TO Specifications. 4. GALVANISING TEST: 15:1367 (Part-13)-1983 (Preece Test 4 dips and coating thl.ckne.ss by thickness gauge) 4.1 Description of the material _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 4.2 Lot .Slze _______________ ..., _ 4.3 Sample Size ______ .J ______ _ 4.4 Acceptance No. ____________ 4.5 Rejection No. _____________ _ 4.6 No. of Deffectlves found ______________________ ~ __ :... '____ _ 4.7 REMARKS: LOT - CONFORMS/DOES NOT CONFORM to Specifications. 5. FINAL REMARKS: LOT ACCEPTED / REJECTED (Refer 1.6,2.6,3.6 &4.5)
n Assn. OFFICER (INSPN.)/INSPECTOR
SR. ENGINEER (INSPN.)
35
QUAUlY CONTROL DEPARTMENT DATE: _ _ _ __
h. TEST REPORT ON PHYSICAL PROPERTIES OF BOLTS Specification: IS:1367 (Part-3) -1979
SIze : ___________________ Grade: _________________ _ Quantify: _________________ Manufacturer: ______________ _ Purchase Order ______________ G.R. Note No.: ______________ _ HEAD SOUNDNESS TEST: - Requirement: No cracks at the neck
(1)
No. of Samples tested _____________ .;. __ Results: _________________ _ Remarks: Lot Accepted/Rejected. HARDNESS TEST: Requirement: minimum __________ maximum _________ _
(2)
Sample No.
Sample No.
Hardness Values In
1
6
2 3
7 8 9
4 5
Hardness Values In
10
Results: __________________ Remarks: Lot Accepted/Rejected PROOF LOAD TEST:- Requirement: Application of kgf for 15 Seconds and adaptor should be removed easily. No. of Samples tested :- ______ Results: _ _ _ _ _ __ Remarks: Lot Accepted/Rejected. (4) WEDGE LOADING (Full Tensile) TEST:- Requirement: - Minimum breaking load _ _ kgf and no crack at neck (3)
Sample No.
Breaking load kgf
Fracture
Sample No.
1
.Breaking load kgf
Fracture
6 7
2 3 4
8 9
5
10 .'
Results :Remarks :- Lot Accepted/Rejected.
(5)
SHEAR TEST:- Requirement: Minimum Shear stress _ _ kgf/mm2
36
Sample
No.
Afeamm2
Shear load kgf
Shear Stress Scmp/e kgf/mm2 No.
1 2
Areamm2
Shear load kgf
Shear Stress
kOf/rT'rn2
6
7 8 9 10
3 4
5
Results:- _ _ _ __ Remarks:- Lot Accepted/Rejected. (6)
FINAL REMARKS: LOT ACCEPTED/REJECTED Test witnessed by:Tests Conducted by
! ~
I
f
I
-1
37
QUALITY CONTROL DEPARTMENT DATE: _ _ _ __
I. TEST REPOm' ON PHYSICAl PROPERTIES OF NUTS Speclflcatlon
size : ___________________ Grade: ______________ - - - ... Quantity:
_________________ Manufacturer: ______________ *
Purchase Order
______________ G.R. Note No.: _ ._____________ _
HARDNESS TEST: Requirement: Minimum __________ HRB Maximum __________ HRB
(1)
Sample No.
Hardness Values In
Hardness Values In
Sample No.
1
6 7 8 9 10
2 3 4 5
Results: __________________ Remarks: Lot Accepted/Rejected (2)
PROOF LOAD TEST:- Requirement: Application of kgf for 15 seconds and mandrel should be removeable by the fingers after the load Is released.
No. of Samples tested :- _ _ _ _ _ Results: _ _ _ _ __ Remarks: Lot Accepted/Rejected.
FINAL REMARKS: LOT ACCEPTED/REJECTED Jest witnessed by:Tests Conducted by
1 S
I
.3Q
.~
I
QUALITY CONTROL DEPARTMENT DATE: _ _ _ __ QCD·3
J. INSPECTION REPORT
FOR SPRING WASHERS Description of Material _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Material Specification IS:3063-1972. Electro Galvanising Specns.lS: 1573-1970 P.O. No. __________________ G.R. Note No. ______________ Supplier _______________________________________ W.O. ___________________ Black/Electro Galvanlsed Date of Receipt ________ ' ______ Date of Inspection ____________
_ _ _ _
SAMPLING SPECIFICATION: IS:6821-1973
1
1. VISUAL INSPECTION 1.1 Lot Size _________________ 1.2 Sample Size _____________ _ 1.3 Acceptance No. (A) Duds _________________ (B) Others _________________ _ 1.4 Rejection No. (A) Duds _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (B) Others ________________ _ 1.5 No. of defectives found (A) Duds _________ .;. ____ (B) Others ________ ,- ______ _ REMARK: LOT - CONFORMS / DOES NOT CONFORM TO SPECIFICATIONS. 2. DIMENSIONAL CHECKING: Details as per 2.6 2.1 Lot Size _________________ 2.2 Sample Size _____________ _ 2.3 Acceptance No. (A) Major _________________ (B) Minor _________________ _ 2.4 Rejection No. (A) Major _________________ (B) Minor _________________ _ 2.5 No. of defectives found (A) Major _ _ _ _ _ _ _ _ _ _ _ _ _ _ (B) Minor _______________ _ REMARK: LOT - CONFORMS / DOES NOT CONFORM TO SPECIFICATIONS. 2.6 Actual Dimensions Descrlpfton
1.0. 0.0.
Width Thickness 2xThlckness
Regulred Dimension for Size M12
M16
M20
M22
12.2+0.8 Max.21.1 4±0.2 2.5±0.15 5+0.3
16.2+0.8 Mox.27.4 5±0.2 3.5±0.2 7±O.4
20.2+1.0 Max.33.6 6±0.2 4±0.2 8+0.4
22.5+1.0 Max.35.9
Actual Dimension
6±0.2 4±O.2 8+0.4
3. PERMANENT SET TEST Size
,IM12
~~
M22
Free Height After 3 Min. Compression Min. Reqd. In mm Actual Min. found In mm
4.25 5.95 6.8 6.8
39
FREE HEIGHT AFTER 20 COMPRESSIONS (As per specifications No further reduction In free height Is permitted)
3.1 Lot Size _____________ ~ ___ 3.2 Sample SIze _____________ _ 3.3 Acceptance No. ____________ 3.4 Rejection No. _____________ _ 3.5 No. of defectives found ______________________________ _ REMARKS: LOT - CONFORMS I DOES NOT CONFORM TO SPECIFICATIONS. 4. TWIST TEST 4.1 Sample Size _______________ 4.2 Acceptance No. ___________ _ 4.3 Rejection No. ______________ 4.4 No. of defectives found ________ _
REMARKS: LOT - CONFORMS I DOES NOT CONFORM TO SPECIFICATIONS 5. HARDNESS TEST: Required Hardness 43 HRC to 50 HRC. 5.1 Sample Size _______________ 5.2 Acceptance No. ___________ _ 5.3 Rejection No. ______________ 5.4 No. of defectives found ________ _ REMARKS: LOT - CONFORMS I DOES NOT CONFORM TO SPECIFICATIONS 6. ELECTRO GALVANISED AS PER IS: 1573-1986 SERVICE CONDITION 3 Lotslze: _________________ _ 6.1 Average Thickness of Coating: Min. reqd-38 Micron. 6.1.1 Sample Size ____________ 6.1.2 Acceptance No. __________ _ 6.1.3 .Rejection No. _ _ _ _ _ _ _ _ _ _ _ 6.1.4 No. of defectives found _ _ _ _ _ _ _ _ REMARKS: LOT - CONFORMS) DOES NOT CONFORM TO SPECIFICATIONS. 6.2 LOCAL THICKNESS OF COATING: MIN. REQD-25Mlcron. 6.2.1 Checking by Magnetic Gauge 6.2.1.1 Sample Size ____________________ 6.2.1.2 Acceptance No. __________________ 6.2.1.3 Rejection No. ___________________ 6.2.1.4 No. of defectives found _______________
_ _ _ _
REMARKS: LOT - CONFORMS I DOES NOT CONFORM TO SPECIFICATIONS. 6.2.2 Microscopic Test: IS:3203-1982 Sampling - 2 pes. per lac or part thereof. 6.2.2.1 Sample Size ____________________ 6.2.2.2 Acceptance No. __________________ 6.2.2.3 Rejection No. ____________________ 6.2.2.4 No. of defectives found _______________ REMARKS: LOT - CONFORMS I DOES NOT CONFORM TO SPECIFICATIONS. FINAL REMARKS: LOT A C C EPTE D IRE J EC TED SR. ENGINEER (INSPN.)
ASSTT. OFFICERIASSTT. ENGINEER
40
_ _ _ _
,
" 3
QUALI1Y CONTROL DEPARTMENT DATE: _ _ _ __ QCD·.
k. INSPEcnONS REPORT F.OR ACCESSORIES Desc~ptlon of Material ________________________________ Material Specification ____________ Drawing No. _______________ Purchase Order No. _____________ G.R. Note No. ______________ Supplier _________________ '______________________ W.O. _' __________________ Black/Galvd. Date of Receipt ________ .:. ____ :- Date of Inspection ________ ...; ___
_ _ _ _ _
--------------------------------------------
SAMPLING SPECIFICATION - IS:2500 (Part-1 )-1973 Inspection level - IV & AQL - 1.5
1. VISUAL INSPECTION 1.1 Lot Size _________________ 1.2 Sample Size _____________ _ 1.3 Acceptance No. ____________ 1.4 Rejection No. _____________ _ 1.5 No. of defectives found _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ' 1.6 Actual defect found _________________________________ 1.7 REMARK LOT: ACCEPTED/REJECTED/lOO% INSPECTION 1.8 100% Inspection Report: Pieces Accepted ____________________ _ Pieces Rejected ____________________ _ 2. DIMENSINAL CHECKING 2.1 Lot Size _________________ 2.2 Sample Size _____________ _ 2.3 Acceptance No. ____________ 2.4 Rejection No. _____________ _ 2.5 No. of defectives found ________ _
2.6 Actual Measurements r-------------~---------------
DESCRIPTION
3. 3.1
___
~------------~
REQUIRED DIMENSION ACTUAL DIMENSION
FINAL REMARKS: FULL LOT ACCEPTED/REJECTED Final Remarks for 100% Inspection: No. of pieces Accepted _ _ _ _ (Refer 1.5 and 2.5) No. of pieces Rejected (Refer 1.5 and 2.5) SR. ENGINEER (INSPN.)
Assn. OFFICER/INSPECTOR
41
QUAliTY CONTI
I. INSPECTIONS REPORT FOR STEEL
TEST TOWER
1. PROJECTjW.O. NO. 2. TOWER TYPE 3. INSPECTION DATE MATE- PURRIAL CHASE IN)ENT ORDER. NO. NO.
DESIGN SECTION
NO. OFPCS
ACTUAL SECTION
LEG LENGTH
YIELD STRESS
REMARKS MAKE ULTI- ELONG. % EMBOSSING MATE TENSILE STRESS
THICKNESS
SR. ENGINEER (INSPN.)
ASSTT. OFFICER/INSPECTOR
42
B. SAMPLING PLAN FOR IN-PROCESS MATERIAL (a) Procedure
1 I 1 i ] ~ J
~
j ~
When a lot Is completed In fabrication and taken for Inspection on stand,.lnltially a piece Is randomly drawn from a lot for detailed Inspection before loading for galvanising. If this piece Is found acceptable further pieces are Inspected by comparison method and loaded. If the first piece does not conform to the requirement and Is rejected the Inspector draws additional pieces as per the follwelng sampling plan which Is In accordance with IS :-2500 (Part 1)-1973, Inspection Level-I. O~
Lot Size
Sample Size
2to 15 16to 50 51 to 150 151 to 500 501 to 1(0)
2 3 5 8
13
All samples drawn according to the above plan should be checked again as per sketch and plant standard. If any piece drawn as per above plan Is found defective, the entire lot should be REJECTED and sent back to the relevant shop. If all the pieces are found acceptable the lot should be accepted and usual Inspection of 100% pieces with respect to 'OK' pieces should be done before loading. Inspection procedure.s of components failing In different categories are categorised separately In full details.
43
QUAlITY CONTROL DEPARTMENT
DATE: _ _ _ __
(b) QUANTITY CONTROL REPORT
c: 12.1.1'12.1.4.1 Item No.
No.
Qty.
Signature of
Quantity
Route Sheet or Plannlnl Memo
Tons.
Reed.
44
Short
Excess
Quality Shop Supervisor INpector for Improper Qty.lfany
Quality Control Department Date _ _ _ __ (c) LOADING REPORT OF CRATES
Sr: I I I
No.
..J
3.
~
4.
l l
5.
Crate Mark
Loading Loading Crate Available Started Completec for Loading
TIme Taken Hours
Weight In Location Tonnes
Remarks Signature of Inspector
1. 2.
6. 7.
-I'
8.
I
9.
J
10.
J
11. 12.
~
l 1 I
14. 15. 16.
-I
:
;
17.
J
18. 19.
~
20.
1 1
21. 22. 23.
1
24.
J
~ ~,
..
13.
25. .
26. ,
,
27. 28. 29.
1
30.
45
Date _ _ _ __ (d) INSPECTION & LOADING REPORT OF FABRICATION SHOP
S H I F T
Crate No.
Route Sheet No.
REJECTION , Code Coupon Slip No. Sample No.
QUANTITY Wt.ln Offered Loaded Rejected kg.fPc.
Item No.
Insp. SIgn.
, Rejection Code
OUT RIGHT REJECTION 0
1
Quantity Total Insoected
Total Relected
2
3
RECTIFIABLE REJECTION
- Others
%ge Rejected
4
5
6
7
8
9
10
11
12
13
14
REMARKS:
1. Store AlC. 2. Fabrication Shop. 3.FIle-QCO. 4. Galv. Shop.
Manager (lnspn.) AC
Others
Dat9 _ _ _ __ (e) INSPECTION a LOADING REPORT OF MODEL ASSEMBLY
I I .I
5
L
H I F T
Crate No.
PI. Memo No.
QUANTITY Wt.ln Offered Loaded Rejected kg./Pc.
Item No.
REJECTION InsSlip No. Code Coupon Sanple pector's No. Sign •
~
-i ~I ~
-1, - I)
-I -J I -I -J I
-I -4 --I I
J ~ Rejection Code
l 1.1 -1
OUT RIGHT REJECTION 1
0
2
3
Others
4
5
6
RECTIFIABLE REJECTION 13 11 12 9 10 7 8
14
Quantity Total Inspected
]
.
!
Total Rejected
%ge Rejected
REMARKS:
1. Store A/C. Fabrication Shop . 3. Flle-QCD. 4. Galv. Shop. ~.
Manager (lnspn.)
47
Others
Date _ _ _ __ (f) INSPECTION a LOADING REPORT OF MODEL SHOP
S H
,
oate No;
F T
Rejection Code
Route Sheet PI. Memo No.
Wt.1n Item No.
kg.fPc.
OUT RIGHT REJECTION
0
1
2
3
REJECTION Slip No. Code Coupon Sample No.
QUANTITY Offered Loaded Rejected
RECTIFIABLE REJECTION
others
4
5
6
7
8
9
10
11
12
13
Quantity Total Insoected
. Total Rejected
%ge Rejected
REMARKS:
1. store AlC. 2. Fabrication Shop. 3.AIe-QCO. 4. Galv. Shop.
Insp.
SVl·
Manager (Inspn.)
14
Others
Date _ _ _ __ (g) OUTRIGHT REJECTION SLIP
,
·
o IN BLACK STAGE
,
Item No.
Qty.
Section
UNIT NO. Length
~
i )
Defect Details:
~
o AFTER GALVANISING Reason
Code
Defects
0
Raw Material
1
Incorrect Section
2 3
Ends Short Holes Wrong Punch
Others
I--
C.C. Dlv. M. (P) I Manager (Scheduling)
i
Inspector
Asstt. Officer (Inspn.) C.C. Supdt./Sr. Foreman
] ~
Sr. Engineer (Inspn.)
i
J ~
1
J ~
1
J ~
1 J
-t 1 -1
i
-I -I
49
Date _ _ _ __ (h) REalflABLE REJECTION SUP
o SHOP: FABRICATION/MODEL ltemNo.
Qty.
Reason
o IN BLACK STAGE
Signature of Sr. Foreman
Signature of
o AFTER GALVANIZING Defects
Code
Q.C.lnspecto~
Remarks
4
Hole Excess
5
End Long
6 7
Bending
8
Chipping
~
Oper. Surface Defects
10
11
Straightening Stamping
12
Hole Mlsslng_
13
Hole out
14
Paint /Bumlng
Open & Close
Others C.C. Shop Foreman INSPECTOR
MANAGER (lnspn.)
C.C. Suptd/Followup
• WHEN THE RECTIFIED ITEMS ARE RECEIVED BACK DULY RECTIFIED.
SG
_
_' .J. _I '_' ...J.-- _, ,_. --1 ...L L
-1. J
(I) WEEKLY RECORDS OF SHIFTWISE ACID STRENGTHS QUAUlY CONTROL DEPT. S H I F T
D A T E
Hydrochloric Acid Tanks
Sulphuric Acid Dichromate Signature of Tank No. Solution Inspector Tank No. Tank No. Tank No. Tank No. Tank No. concentraSpec. WN Spec. WN Spec. WN Spec. WN Spec. WN Spec. WN tlon By gravity glUt. gravity g/lit. grqvity glUt. grqvtty g/lit. gravity g/lit. gravitY gIl It. colour • • • • • .& ~e 'Be '~Be dSBe ·~Be comparison 1~27 180-40 1~27 180-40 1~27 180-40 1~27 180-40 1~27 180-40 11-28 150-40 1.2 - 1.5
.
B C
D B C
0'1 .......
0 B C 0
B C
0 B C --
D
·Percentage concentraHon Is one tenth of the values specified In the column. SR. ENGINEER (INSPN.) QUAUlY CONTROl & INSPN.
QUAUlY CONTROL DEPARTMENT DATE _ _ _ _ __ (j) GALVANISING PROCESS INSPECTION REPORT
CONCENTRAnON OF DEGREASING AND PREFLUXING SOLUTION % recommendation
% Iron content
Prefluxlng solution
16to 30'
Max. 0.5'
.Degreaslng solution
4 to 10'
1.
Specified
a) b)
I
16%
Concentration means
160 g/I.
I
4%
Concentration means
4Og/l.
I
0.5%
Iron content means
5g/l.
2. 3.
Frequency of testing weekly Actual percentage concentration found SAMPLE DRAWN ON TEST REPORT
Sr. No. Description
% ConcentraHon
% Iron content
Remarks
A
Prefluxlng Solution (Main Tank)
SATISFACTORY/ NOT SATISFACTORY
A1
Prefluxlng Solution (B/N & Accessortes Tank)
SATISFACTORY/ NOT SATISFACTORY
Degreaslng Solution (Main Tank)
SATISFACTORY/ NOT SATISFACTORY
B
You ore requested to make necessary arrangements to achieve the specified percentage •concentration and iron content, where it is not satisfactory before using the solutions. cc: Galvanizing Deptt. OFFICER (INSPECTION) QUAUlY CONTROL DEPlT
~ \
t-
~
I L 52
Q.C.D. DATE:
(k) GALVANISING INSPECTION REPORT
~II=T'
~NCBATIYTEMPERA]uRES
. TIME
MAIN BATH
AUX. BATIY
N. &B.BATIY ,
ZINC COATING REPORT OF SAMPLES @
Section
1
2
3
4
5
Ava.
DIp· llAd.T.
Item No.
1 2
3 4
5 6 7 ACC GALVANISING REJECTION FOR REWORK (VISUAL INSPN.) Item No.
Qtv.
Code
Colour
Item No.
Total Pcs.lnspected
Qtv.
Code
Colour
Total Pes. Rejected P.T.O.
53
Code 0
D Q.C.D.Flle
1
Unclckled Black/Bare Sco1s Flux Inclusions
2) Divisional Manager (Prodn[Schedullng)
2
Rough SUrface, lumpiness, Pimples, Hard Zinc
~l
3
Peeling, Flaking Off
4
Others
INSPECTOR
OFFICER (lNSPN.)
NOTE: • Preece test: No. of dips of one minute each. @ 1 to 4 values In microns, 5 to 7 In g/sq. m. A Adhesion test: By hammer blows/prying by knife
Galvanlsloo Dept.
MANAGER (INSPN.)
MINIMUM REQUIREMENTS 610 g/sq.m. for structural steel 86 Microns for structural steel 43 Microns for hardware & B/N Optimum Temeroture range 450°C to 465°C
QUALITY CONTROL DEPARTMENT
"1
(I)TESTING CONCENTRAnON OF PREFLUXING AND DEGREASING SOLUnONS
I j
-i
TO: QUALITY CONTROL LABORATORY
SAMPLE SENT ON DATE
The following samples are sent herewith for finding out percentage concentration/percentage Iron content as follows. Kindly send the results at the earliest. Sr. No. Description
A
Prefluxlng Solutlon (Main Tank)
A1
Prefluxlng Solutlon (BIN & Accessories Tank)
B
No. of sample sent
Concentration percentage
Percentage Iron Content
Degreaslng Solution
(SIGNATURE)
(SIGNATURE OF RECEIVER) Q.C.D. LABORATORY
55
APPENDIX II Ust of Machines required for a well equipped Tower Fabricating Workshop Monthly Production
500 Tonnes
1.
Roller Straightener
One
2. 3. 4. 5.
Hammer Straightener
Two
Screw Press Bending Machine
Two
Hydraulic Press Bending Machine
One
Ball Point Bending Machine
One
6.
Universal Machine (Punching, Cropping, Shearing, Notching), (For tower manufacturing universal machine Is not favoured because stacking of materials for two or more operations Is very difficult)
One
7.
Single Operation Machine for Cropping
Two
8.
2~M-orm
One
9.
Single operation Machine for punching (automatic machine preferable).
Two
10.
Single Operation Machine for Notching
One
11.
Ole-punch Masking Machine
One
12.
Stencilling Machine
One
13.
Circular Saw
One
14.
Gas cutting (mechanically guided)
One
15.
Gas-cuttlng Torches
Three sets
16.
Portable Grinder
Three
17.
Field Grinder
Two
heavy radial drilling
56
APPENDIX III WORKSHOP CHART Sr. No.
Operation
Symbol
Machine
31
Straightening
Roller stralghtner, Hammer Stralghtner.
32
Bending
Screw press, Hydraulic press, . . point press
33
Cropping sheartng, gascuttlng
34
Punching
No. of Operations Involved
Remarks
~
Both on flfnge and heel
~
Universal machine, Cropping machine (single operOtlon)
Ufllversal machine
May be one or
more diameters Drtlllng Joggling
-.-:... ~J
a
I
!$
~members fitting over
t~rtng fltes
x
Its:::&:~
~
i'v
.....
Bevel cut
~~.----
Comer cut
~
Required to provide clearance against fouling Required to provide clearance against fouling Required to provide clearance against fouling
)(
Flange cutl Flange reduction
0-
Required on covel ee€'Jts and I~ joint.
{~ ,.Ii
Notch
May be one or more diameters
On lettlce In c~se laid In different planes
L
Heel chamfer Closing or opening
Radial drtlllng
~ x .. ., -J:..1-
Required to provide clearance against fouling
r=t •• ~~.
57
APPENDIX IV Process Flow Chart for Fabrication of Tower Detail drawing Floor layout and shop drawing Material procurement Proto manufacture Assembly of tower Proto test and approval Mass fabrication Marking Galvanising
Bundling
Despatch
58
A. Bibliography 1.
Manual of steel construction by American /institute of steel construction.
2.
Structural shop drafting by American Institute of steel construction .
3.
American Society of Civil Engineers Manual No. 52 - 1988 MGuide for Design of Steel Transmission Towers"
B.
LIst of Indian Standards required for references for this paper.
.
IS - 800 IS - 802 Part I, " & 11/ IS - 962 IS· 808 -1989 IS - 2062 - 1992 IS - 1852 - 1985 IS· 6639 ·1972 IS-1367IS - 4218 (p'art iii - 1976) IS ·12427·1992 IS - 2500 Part I - 1973 is· 2614·1969 IS - 6821 - 1973 IS - 209 - 1979 IS - 1363 - 1984 IS - 2629 - 1985 IS - 2633 - 1986 IS -·209 - 1979 IS - 7215 ·1974 IS - 3063 - 1994 IS - 13229 - 1991 IS - 1270 - 1965
59
Transmission Line Manual Chapter 10
Design of Foundations
CONTENTS Page 10.1 General 10.2 Types of Loads on Foundations 10.3 Basic Design Requirements
10.19 Foundation Defects and their Repairs
1 1 2 2 2 3 4 26 26 29 37 37 41 41 42 44 45 45 46
Annexures ANNEXURE-I ANNEXURE-IT ANNEXURE-ill ANNEXURE-IV ANNEXURE-V
49 50 51 53 54
Typical Ulustration for Examples of Design Circulation Illustration-I Illustratioft-IT Illustration-III Illustration-IV Illustration-V Illustration-VI Illustration-VII Illustration-VIII Illustration-IX Ulustration-X Illustration-XI
55 55 70 73 75 76 79 81 83 86 88
10.4 Soil Parameters 10.5 Soil Investigation 10.6 Types of Soil and Rock 10.7 Types of Foundations 10.8 Revetment on Foundation 10.9 Soil Resistances for Designing Foundation 10.10 Design Procedure for Foundation 10.11 Concrete Technology for Tower Foundation Designs 10.12 Pull-out Tests on Tower Foundation 10.13 Skin Friction Tests 10.14 Scale Down Models of Foundation 10.15 Tests on Submerged Soils 10.16 Investigation of Foundation of Towers 10.17 Investigation of Foundation of a Tower Line in Service 10.18 Repairs of Foundations of a Tower Line in Service
(
.t 1
CHAPTER - 10
DESIGN OF FOUNDATIONS 10.1
GENERAL
10.1.1 Foundation of any structure plays an important role in safety and satisfactory performance of the structure as it transmits the loads from structure to earth. Without having a sound and safe foundation, structure can not perform the functions for which it has been designed. Therefore, the importance of foundation need not be over-emphasized. The sizes of transmission line towers are Increasing because of the present dgy high, extra high and ultra high voltage transmission, resulting In heavier loads and as such requiring bigger and heavier foundations. A large number of foundations are normally required in any transmission line project. Thus. the total cost of foundations in a transmission line project becomes quite substantial. Apart from the financial aspects. past records show that failures of tower foundations have also been responsible for collapse of towers. These failures have usually been associated with certain deficiencies either In the design or classification or construction of foundations. Many times. foundations cast are over safe because of inappropriate classification. resulting In wastage of resources .. From engineering point of view. the task of design and selection of most suitable type of tower foundation Is challenging because of the variety of soil conditions encountered enroute the transmission line and remoteness of construction sites. The foundations In various types of soils have to be designed to suit the soil conditions of particular type. In addition to foundations of normal towers. there are situations where one has to decide the most suitable type of foundation system considering techno-economical aspects for special towers required for river crOSSing which may be located either on the bank of the river or In the mid stream or both. This is generally decided based on the actual river crossing requirements; and the choice of type of foundation and it's design would be based on actual soil exploration data, high flood level, velocity of water. scour depth etc. However. the design of special foundations Is not covered in this manual and would be dealt with seperately. 10.1.2 As the concept of safe value for properties of soli has been dispensed with In the design of foundation. limit value of properties of soli should be obtained from soli Investigation report. 10.1.3 This chapter does not cover the monoblock foundation. 10.2
TYPES OF LOADS ON FOUNDATIONS
The foundations of towers are normally subjected to three types of forces. These are : (a) (b) (c)
the compression or downward thrust: the tension or uplift; and the lateral forces or side thrusts In both transverse and longitudinal directions.
The magnitudes of each of these forces depend on the types of tower and the transmission capacl1y of lines. The method of calculating above loads Is described In detail In Chapter-6 - LOCA.dU.''''jJ·ln this mOnual. The magnitudes of limit loads for foundations should be taken 10% higher than those for the corresponding towers.
1
10.3
BASIC DESIGN REQUIREMENTS
To meet the varying needs in respect of soil conditions and loading quantum, several types of tower foundations have been used for the transmission line towers. Design philosophy of tower foundation should be closely related to the principles adopted for the design of the tower which the foundation has to support. A weak or unsound foundation can make a good tower design useless while a very strong foundation for a weak tower means a wasteful expenditure. Functionally, the foundation should be strong and stable. It should take care of all the loads such as dead loads, live loads, wind loads. seismic loads, erection loads etc. causing vertical thrust. uplift as well as horizontal reactions. For satisfactory perform once, it should be stable and structurally adequate and be able to transmit these forces to the soil such that the limit soil bearing capacities are not exceeded.
10.4
SOIL PARAMETERS
For designing the foundations, following parameters are required: (a) (b) (c)
Umit bearing capacity of Soil; Density of soil; and Angle of Earth frustum.
These soil properties are normally obtained either by conducting in-situ or laboratory tests on soil samples collected from the field during Soil Investigation or from available testing record of the area. The importance of above soil parameters in foundation deSign is discussed below in brief. Umlt Bearing Capacity
This parameter is vital from the point of view of establishing the stability of foundation against shear failure of soil and excessive settlement of foundation when foundation is subjected to total downward loads and moments due to horizontal shears and/or eccentricities as applicable. Recommended limit bearing capaCities of various types of soil are given in Annexure - I for guidance. These will be reviewed when more reliable data are available. Density of Soli
This parameter is required to calculate the uplift resistance of foundation. Recommended unit weights of various types of soil are given in Annexure - I. Angle of Earth FNstum
This parameter is required for finding out the uplift resistance of the foundation. Recommended values of angle of earth frustum for different types of soils/rocks are given In Annexure - I. 10.5
SOIL INVESTIGATION
The design of the tower foundation is fully dependent upon conditions of the soil that will support the foundation and the nature of loadings. It is, therefore, necessary to investigate the soil for it's engineering properties. There are number of procedures for collection of soil data covered in various Indian Standard Codes of Practice like IS:1892, IS:1888, IS:2131, etc. and standard books on Soil Mechanics and Foundation Engineering. Selection of anyone of these depends on the suitability and merits of the procedure for a given soil condition as well as it's relative cost compared to the cost of the proposed structure.
It Is desirable to carry ?ut detailed soli Investigation on the Railway crOssing ~atIonS: heavy angle tower locations, at an.1nten:'al of 15 locations along the route'and also where soil strata changes, at the descreHon of Englneer-In-charge. The detailed soli invesHgaHon for special river crossing tower locaHon Is a must. y
In areas which have already been developed, advantage should be taken of the existing local knowledge, records of trial pits, bore-holes, etc. In the vicinity. If the existing InformaHon Is not sufficient, It is necessary to explore the site to obtain details of the type, uniformity, consistency, thickness, depth of the strata and the ground water conditions. In many cases of transmission line' works, the soli invesHgatlon may consist of only exploratory test pits and laboratory tesHng of some selected soil samples.
(.
s )r .(
The details of solllnvesHgatlon' are not covered In this chapter and may be referred to In the relevant text books and Indian Standards available for the purpose. However, the list of the tests to be carried out is given In Annexure - ,II. These tests are aimed at finding out type of soli, density, limit becirrng capacity, angle of earth frustum, water table. etc. DuringexecuHon, trial pits upto a minimum depth of 3.0 m (except for hard rock locaHons) shall be excavated at each and every tower locaHons (at all four legs) to obtain follOwing details In order to classify the type of foundation to be adopted: ~.
0) Oi)
Type of soil encountered Ground water table.
10.6
TYPES OF SOIL AND ROCK
Solis and rocks, based on their engineering and physical properties, can be broadly classified as under: Types of Soil Non-cohesive Sol/s
e.
(0)
,ts
This group of soils include gravel and sands which are composed mainly of Iqrger siied grains resulting from weathering of rocks. The engineering behaviour of these soils under loading depends primarily on their friction qualities which vary with their density, degree of lateral confinement, grQund water level and flow of water through them. The non-coheslve solis do not get unified with the parent soli after back filling with the passage of Hme. The following type of solis come under this category : Sandy Soils which have no clay Isllt or have very little clayIsllt
es
"'Ie
t'
(II)
Soft and hard murrum. These can be excavated using normal tools and these get diSintegrated Into pieces
(b)
Cohesive Soils
These comprise clays, silts and soft shales, etc. having comparaHvely fine grain size particles. The strength of this group of soils is derived primarily from cohesion between their particles. The most important characteristic of cohesive solis from engineering point of view Is their suscepHbllity for slow volume changes due to their low permeability. When this type of solis are subjected to loads, the contained water in the voids Is expelled very slowly with consequent diminution of volume resulting In consolidation settlement. Unlike settlement In non-cohesive so/ls which Is Immediate, the settlement in cohesive solis may take many years to reach It's final value. In cohesive so/ls, SPT test does not always
3
giVe depet\dable results,. partlculai1y In sensitive cloys; and undisturbed soH samples are required to be tested In the laboratory for It's unit weight, moisture content confined and unconfined compressive strengths and settlement chciroctei1stics.
The cohesive soils get unified with the parent soil after bock filling with the passage of time. The following soBs cOme under this category:
NorrndI soH hovIhg mixture of slit and clay (clciy not exceeding 15%). When this type 6f soil Is rnoc:te wet and rolled betWeen the palms, only short threadS can be mode. ..
(I)
00
Clayae solis having high percentage of cloy (more than 15%) e.g. Block Cotton Soli (Black or yellow In colour). When this type of soli Is made wet and rolled between the palriis, long threads can be made. Mai'SHy SOIl hdVlng sea mud (marine soli) which Is very sticky In nature.
011) .
.
Types ci Rocb
Rocks derive their strength from permanent bond of cohesive forces among their particles. They ar~ usually c~ as· hard, and sOft. Rocks have hlgli bearing capacity except When deComposed heavily shattered ot strcrlltied. uneveh site, however, dangerous conditions riiay develop wItH rock~ If they dip towards cuttings. Tower foundations are usualiy built on the upper ared df the rock formationS WhIch are often found to be weathered and disintegrated.
On
The rocks Ore broadly classified Os follows: (0)
SOft Rock/FISSured Rock
The rocks WhICh can be excavated USing normal tools without blasting are classified as soft rock. These Include dEk:omposed or fissured rock, hard gravel, konkar, lime stone, laterite or any other sOIl of Similar nature. (b)
Hard Rock
The rocks Which cannot be excavated using normdl tools and require chiseling, drilling and blasting are classJfled os Hard Rock. These Include hard sand stone, quartilte, granite, bosdit, hard marble, e~c.
cOITIbInaIIons Of SolIs During execution for any transmission line project It Is possible that combination of two or more than two types of soils may also occur, while excavating the soil upto founding level. Different combinations of soils a.nd the types of foundations to be adopted are given in annexure - III.
10.7
TYPES OF FOUNDATIONS
Depending upon the ground water table and type of soil and rock, the foundations can be classified as follows:
(a)
Normal Dry Soil Foundations
When water table is below foundation level and when soli Is cohesive and homogeneous up to the full depth having clay content of 10-15% . (b)
Wet Soil Foundatjo~ .
\A/h.o.n u/"ti:l., t"h~ I~ rihnvA fnllnrlntlnn
lAVAl and UD to 1.5 m below around level. The foundations in
the soils which have standing surface water for a long period with water penetration not exceeding 1.0 m below ground level (e.g. paddy fields) are also classified as wet foundations. (c)
Partially Submerged Foundations
When water table is at a depth between 1.5 m and 0.75 m below ground level and when the sallis normal and cohesive. (d)
Fully Submerged Foundations
When water table is within 0.75m below ground and the soil is normal and cohesive. (e)
Black Coffon Soil Foundations
When the soil is cohesive having inorganic clay exceeding 15% and characterised by high shrinkage and swelling property (need not be always black in colour).
e
(f)
(S :1,.
When the top layer of soil up to 1.5 m Is Black Cotton and thereafter It Is normal dry cohesive soli.
1!
(g)
Partial Black Coffon Foundations
Soft Rock/Fissured Rock Foundations
When decomposed or fissured rock, hard gravel or any other soil of similar nature Is met which can be executed without blasting. Under cut foundation is to be used at these locations.
e l'
(h)
Hard Rock Foundations
Where chiseling, drilling and blasting is required for excavation. (i)
Sandy Soil Foundations
Soil with negligible cohesion because of it's low clay content (0-10%). The above categorization of foundations has been done for economising the foundations. as uplift resistance of foundation is a critical design factor which Is greatly affected by the location of water table and the soil surrounding the foundation. .
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10.7.1 Structural Arrangement of Foundations Based on structural arrangement of foundations, the various types of foundations are possible. The necessity of erecting towers on a variety of solis has made it possible and necessary for the designers to adopt new Innovations and techniques. As a result. several types of tower foundations have been devised and successfully used. Some of the more common types of foundations are described below: (a)
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P.C.c. Type
This type of foundation is shown in Figure I. This is the most common type of footing used In India and in some countries of the continent. It consists of a plain concrete footing pad with reinforced chimney. In this type of foundation, the stub angle is taken inside and effectively anchored to the bottom pad by cleat angles and/or keying rods, and the chimney with reinforcement & stub Qngle Inside works as a composite member. The pad may be either pyramidal in shape as shown In Figure 1(0) or stepped as shown in Figure 1(b). Stepped footings will require less shuttering materials but need more attention during construction to avoid cold-joints between the steps. The pyramidal footings, on the other hand,
5
will require somewhat costlier form work. In this pad and chimney type footing, where the chimney Is comparatively slender, the lateral load acting at the top of the chimney will cause bending moment and, therefore, the chimney should be checked for combined stresses due to direct PlJll/thrust and bending.
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Figure I (b):.P C.C.Type Stepped Foundation 7
If the soil is very hard, conglomerate of soil, containing stones, rubbles, Kahkar which tan be loosened with the help of pick-axe or if the soil is of composite nature i.e" combihation of ho~mal dry soli. hard murrum, fissured rock which will not get unified easily with the parent soil atter back filling, pyramid chimney type foundations having 150 mm side clearance are not advisable and in such cases undercut/stepped footings without side clearance should be adopted. (b)
R.C.C. Spread Type
Typical types of R.C.C. Spread Footings are shown in Figure 2. It consists of a R.C.C. base Slab or mat and a square chimney. There are several types of R.C.C. spread footings which can be designed for tower foundations. The three most common types of these are shown In Figures 2 (a), (b) & (c). As shown in the figures. this type of foundation can be either Single step type or multiple step type and/or chamfered step type.
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Spread Type Foundation (Step) with 1S'Omm Working Clearance
The R.C.C. spread type footings can be suitably designed for variety of soil conditions. R.C.C. footings. in some situations may be higher in cost although structurally these are the best.
9
When loads on foundations are heavy and/or soil is poor. the pyramid type foundations may not be feasible from techno-economical considerations and under such situations. R.C.C. spread type footings are technically superior and also economical. R.C.C. spread footing with bottom step/slab when cast in contact with Inner surface of excavated soil will offer higher uplift resistance as compared to the footing having 150 mm side clearance as shown in Figure 2(c).
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Figure 2(eJ: R.Le. Spread Type Foundation (Step) Cast Directly Contact with the Soil & without 1S0mm WorkinQ Clearance
(c)
Block Type
This type of foundation Is shown in Figures 3 & 5 (a). It consists of a chimney and block of concrete. This type of foundation is usually provided where soft rock and hard rock strata are encountered at the tower location. In this type of foundation, concrete is poured in direct contact with the inner surfaces of the excavated rock so that concrete develops bond with rock. The uplift resistance in this type of footing Is provided by the bond between concrete and rock. The thickness and size of the block Is decided based on uplift capacity of foundation and bearing area required. It is advisable to have footing having a minimum depth of about 1.5 m below ground level and check this foundation for the failure of bond between rock and concrete. The values of ultimate bond stress between the rock and the concrete to be considered for various types of rocks are given in Annexure-iV for guidance. However, the actual bond stress between rock and concrete can be decided by tests. Block type foundations are being provided by some power utilities for soft and hard rock strata. However, under cut type of foundations for soft rock and rock anchor type of foundations for hard rock are sometimes preferred by some power utilities because of their soundness even though thes.e may be more costly in comparison with Block type foundations. (d)
Under-Cut Type
These type of foundations are shown In Figures 4 (a),(b) & (c). These are constructed by making under-cut in soil/rock at foundation level. this type of foundation Is very useful in normal dry cohesive soil, hard murrum, fissured/soft rock, solis mixed with clinker, where soli is not collapsible type i.e.. it can stand by itself. A footing with an under-cut generally develops higher uplift resistance as compared to that of an identical footing without under-cut. this is due to the anchorage in undisturbed virgin soil. The size of under-cut shall not be less than 150 mm. At the descretion of power utility and based on the cohesiveness of the normal dry soil, the owner may permit undercut type of foundation for normal dry cohesive soil. (e)
Grouted Rock and Rock Anchor Type
Typical Grouted Rock and Rock Anchor type,footing is shown in Figure 5(b). This type of footing is suitable when the rock is very hard. It consists of two parts viz. block of small depth followed by anchor bars embeded in the Grouted Anchor Holes. The top part of the bsu is embeded in the concrete of the shallow block. The depth of embedment. diameter and number of anchor bars will depend upon the uplift force on the footing. The diameter shall not be less than 12 mm. The grouting hole shall normally be 20 mm more than the diameter of the bar. .. The determination of whether a rock formation is suitable for installation of rock anchors is an engineering judgement based on rock quality. Since, the bearing capacity of rock is usually much greater, care must be exercised in designing for uplift. The rock surfaces may be roughened, grooved. or shaped to increase the uplift capacity. The uplift resistance will be determined by considering the bond between reinforcement bar and grout/concrete. However. an independent check for uplift resistance should be carried out by conSidering the bond between rock & concrete block which in turn will determine the min. depth of concrete block to be provided In hard rock. Anchor strength can be substantially increased by provision of mechanical anchorages. such as use of eye- bolt. fox bolt or thread~d rods as anchoring bars or use of keying rods in case of stub angle anchoring. The effective anchoring strength should preferably be determined by testing. "
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Figure 4 (a ) : Pyramid Type Foundation (with under-cut)
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Figure 4 (b): R. C. C. Spread Type Foundation (Under Cut Type)
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17
Open cast Rock foundation is not recommended in Hard Rock. However, where rock anchor 1ype foundation Is not practicable, open cast rock type foundation may be adopted as a special case. (f)
Augur Type/Under Reamed Pile Type
Typical types of foundations are shown In Figure 6(a). The cast-In-situ reinforced concrete augured footings have been extensively used in some westem countries like USA. Canada and many countries in our continent. The primary benefits derived from this type of foundations are the. saving In time and man-power. Usually a truck mounted power augur is utilised to drill a circular hole of required diameter, the lower portion of this may be belled, If required, to a larger diameter to Increase the uplift resistance of the footing. Holes can be driven upto one metre in diameter and six metre deep. Since, the excavated hole has to stand for some time before reinforcing bars and cage can be placed In position and concrete poured, all kinds of solis are not suitable for augured footing. Usually, stiff clays and dense sands ar~. capable of being drilled and standing up suffiCiently long for concreting works and Installation of stub angle or anchor bolts, whereas loose granular materials may give trouble during construction of these footings, Bentonite slurry or similar material is used to stabilise the drilled hole. In soft soils, a steel casing can also be lowered Into the hole as the excavation proceeds, to hold the hole open. Uplift resistance of augured footing without bell Is provided by the friction along the surface of the shaft alone and hence it's capacity to resist uplift is limited. Augured footing can be constructed according to the requirement, vertical or battered and with or without expanded base. (g)
Under-Reamed Pile Type
The under-reamed piles are more or leSs similar to augured footings except that they have under reaming above bottom of shaft. These can be generally constructed with hand augur. The bore Is drilled vertically or at a batter with the augur, having an arrangement of cutting flanges (edges) to be opened by the lever. This arrangement makes it possible to make under-reams at various level of bores as shown in Figure 6(b). The advantage of this foundation is foster construction. The load carrying capacity of these footings, both for downward and uplift forces should be established by tests. The safe loads allowed on under-reamed piles of length 3.50 m and under reamed to 2.5 times the shaft diameter in clayey, black cotton and medium dense sandy solis may be taken from IS: 4091 for guidance. These types of foundation are useful in case of expansive type of block cotton soils. (h)
Steel Grillage Type
These types of foundation are shown in Figures 7(a)&(b). These are made of structural steel sections. Steel grillages can be of various designs. Generally, it consists of a layer of steel beams as pad for the bearing area. The footing reaction Is transmitted to the pad by means of heavier joists or channels resting cross-ways on the bearing beams. For smaller towers, the horizontal shears at foundation from the component of force In the diagonal members is transferred to the adjoining soil by shear plates of adequate size proyided at the point where the bottom most diagonal bracings Intersect the main leg/stub usually about a metre below the ground surface as shown in Figure 7 (a). In case of heavy towers like angle or dead end, the lateral·force is taken up by addition of suitable bracing members shown in Figure 7 (b) which trdnsfer the shear down to the grillage beams.
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Figure 6(b): Augur Type Foundation (Unde,r Reamed Pi Ie Type)
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Figure 7(a): Steel Grillage Type Foundation
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Figure 7 ( b) : Steel Grillage Type Foundation
The grillage Is designed to resist the down thrust and uplift. The angle of earth frustum Is developed from the bottom of the footing. In this type of foundations, there is no solid slab as compared to concrete foundations. However, if the distance between the grillage members is not greater than the width of members, the gross area of grillage can be utilised in calculating bearing pressure. If the distance between members is large, only the net area of grillage can be taken into account for calculating the bearing pressure on the soil. The placement and compaction of the backfill is very critical to the actual load carrying capacity of this type of foundations. As a precaution against corrosion, a coot of bituminous paint is usually applied to the footing. When backfill Is well compacted to eliminate air pockets, the lower portion of the footing may not suffer any appreCiable corrosion of steel. Weathering steel or galvanised steel can also reduce the chances of corrosion, but none of these can prevent corrosion when the soil at the tower location is unfavourable and chemically aggressive. When doubt arises, It may be necessary to test the soil and sub-soil water samples to ascertain their corrosiveness before using a steel grillage footing. Grillage footings require much more steel than a comparable concrete footing, but erection cost is small in comparison to that of the concrete footing resuMing in often economical and always quicker construction. Other advantages include their simplicity in construction procurement of complete foundation with tower parts from the manufacturer of towers and elimination of concrete work at site. These foundations are also very helpful in restoring the collapsed transmission lines because of quicker construction. The disadvantage of this type of foundation is that these foundations have to be designed before any soil borings are made and may have to be enlarged and require a concrete base if actual soli conditions are not as good as those assumed in the original design. These types of foundation are generally provided in case of firm soils and are usually adopted for locations where concreting is not possible and head loading is difficult. This type of foundation is not . popular in our country. (i)
Steel Plated Type
A typical pressed steel plate foundation is shown in Figure 8. This arrangement is similar to the steel grill foundation shown in Figure 8 except that the base grillage has been replaced by a pressed steel plate. This type of foundation Is usually adopted for locations where concreting work is not possible and head loading is difficult. This type of foundation is suitable only In case of good, cohesive and firm soil. The size of plate is decided based on uplift capacity required and also based on footing area necessary from bearing capacity consideration. The net horizontal force at the level where bottom most diagonal bracing Is attached to the stub is resisted by the passive pressure of -the soil. The advantage of this type of foundation Is It's simpliCity. However, one has to be careful in excavation at the bottom .. The plate must rest firmly In contact with the surrounding soli. The disadvantage of this type of foundation is possibility of corrosion of steel and large settlement because of loose sand under the plate. This type of foundation is not popular in our country. G)
Pile Type
A typical pile type foundation is shown In Figure 9. This type of foundation is usually adopted when soil is very weak and has very poor bearing capacity or foundation has to be located In filled-up soli or sea mud to a large depth or where tower location falls within river bed and creek bed which are likely to get scourea during floods.
23
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Figure 8: Steel ,Plate Type Foundation
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Figure 9: Pile Type Foundation 25
The pile foundations are designed based on the data of soil exploration at the tower location. The 1mPOrtant parometers for design of pUe foundation are the type of soli, angle of Intemal friction, cohesion and unit weight of soil at various depths along the shaft of pile, maximum discharge of the river, maximum velocity of water, high flood level, scour depth etc. Pile foundation usually costs more and may be adopted only after detailed examination of the site condition and soil data. The downward vertical load on the foundation is carried by the plies through skin friction or by point bearing or both: while the uplift is resisted by the dead weight of the concrete In piles and pile caps and frictional resistance between pile and soU surrounding the pile. For carrying heavy lateral loads, battered piles may be advantageously used. Piles are of different types such as driven pre-cast piles, cast-In-sltu concrete bored piles and cast-in-situ concrete driven piles. Concrete driven piles whether pre-cast or cast-in-sltu, require heavy machinery for their construction and as such may not be possible to use for transmission line foundations because of remoteness of the sites and smail volume of work~ Mostly, cast-In-sltu concrete bored piles are provided In transmission line proJects since, they do not require heavy machinery for their construction. Load carrying capacitY of different types of piles should normaily be established by load tests. When It Is not possible to carry out load tests, the capacity of pile can be determined by static formula as given In IS: 2911 using soil properties obtained from soil investigation of tower location where pile foundation is proposed to be provided. (k)
Well Type
A typical well type of foundation for transmission line tower is shown in Figure 10. This type of foundation Is usually provided where tower location falls within the course of major river having larger discharge, heavy floods during monsoon and large scouring of river bed during floods. The cast-In-sltu weils of R.C.C. or brick masonary are sunk by continuous excavation from within the wells. The basic parameters required for the design of well are soil properties like angle of internal friction, cohesion, and density at various levels along the depth of well, maximum flood discharge, maximum velocity of water, the scour depth, etc. The well has to be taken below the estimated scour level to a sufficient depth for obtaining desired load carrying capacity of the well. Kentel edge may have to be used during sinking of the well for penetrating the hard strata and also to prevent it's tilting during sinking operation. The top of the wells is normally kept above the high flood level. After the well has been sunk to It's design depth, the well Is filled up with sand and suitable well cap Is constructed on the top of the well to accommodate the tower and it's anchor bolts/stubs. The filled up well acts as solid pier. Well type foundations are very costly and require more time for their construction and may be adopted only after detailed examination of the site condition and soil data. 10.8
REVETMENT ON FOUNDATION
The revetment on foundation is usually required when the tower is to be founded on a slope of hill or in deserts where there is possibility of soil flying away during dust storm. The typical details of revetment for hilly location are shown in Figure 11. The bench cutting is first done to level the siope. The foundation is cast with shorter and longer stubs If it is not possible to fully level the slope. Revetment is necessary to prevent erosion of soil due to water flow from uphill and also to ensure proper anchorage against uplift. . 10.9
SOIL RESISTANCES FOR DESIGNING FOUNDATION
As discussed in para 10.2, the foundations of Transmission line towers are subjected to three types of . loads viz. the downward thrust (compression), the uplift (tension) and the side thrust (horizontal shear)..
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Scouring action
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Figure 10: Well Type Foundation 27
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Figure 11: Rivetment on Foundation The soil resistances available for transferring the above forces to earth are described below: (a)
Uplift Resistance
The soil surrounding a tower foundation has to resist a considerable amount of upward force (tension). In fact, In the case of self-supporting towers, the available uplift resistance of the soli becomes the most decisive factor for selection of the type of footing for a particular location. It is generally considered that the resistance to uplift is provided by the shear strength of the surrounding soli and the weight of the foundation. Various empirical relationships linking ultimate up-lift capacity of foundation to the physical properties of soil like angle of Internal friction (t/» and cohesion (C) as well as to the dimensions and depth of the footing have been proposed on the basis of experimental results. However, the angle of earth frustum Is considered for calculating the uplift resistance of soil. Typical values of angle of earth frustum are given In Annexure -I for guidance. The angle of earth frustum is taken as 2/3 of angle of Internal friction (t/» or the value given In Annexure I I. _ _ _ .. aJl ..... : _ ...... _
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The uplift resistance is estimated by co uti th . of cone whose sides make an angle ;e formula for calculating volume covered under Inverted frustum of a cone is given in Annexure-V.
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It shoUI?, how~v~r, be noted that effective uplift resistance, apart from being a function of the properties of sOil like angle of intemal friction (¢J) and cohesion (C) is greatly affected by the degree of co,:,pactlon and the ground water table. When the back fill Is less consolidated with non-cohesive matena!, the effective uplift resistance will be greatly reduced. In case of foundation under water table, the buoyant weights of concrete and back fill are only considered to be effective. The uplift resistance of footing with undercut projections within undisturbed soils in firm non-cohesive soils and fissured/soft rock shall generally be larger than that of conventional footings. (b)
Lateral Soil Resistance
In foundation design of towers. the side thrusts (horizontal shears) on the foundation are considered to be resisted by the passive earth pressure mobilized in the adjoining soils due to rotation of the footing. Passive pressure/resistance of soil is calculated based on Rankine's formula for frictional soils and unconfined compressive strength for cohesive soils. (c)
Bearing Capacity
The downward compressive loads acting on the foundation including moments du~ to horizontal shears and/or eccentricities, wherever existing. are transferred from the foundation to earth through be.drtng capacity of the soil. The limit bearing capacity of soil is the maximum downward intensity of load which the soil can resist without shear failure or excessive settlement.
10.10
DESIGN PROCEDURE FOR FOUNDATION
The design of any foundation consists of following two parts :
(1)
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Stability Analysis
Stability analysis aims at removing the possibility of failure of foundation by tilting, overtuming, uprooting, and sliding due to load intensity imposed on soli by foundation being In excess of the ultimate capacity of the soil. The most important aspect of the foundation design is the necessary check for the stability of foundation under various loads imposed on it by the tower which it supports. The foundation shOUld remain stable under all the possible combinations of loadings, to which It Is likely to be subjected under the most stringent conditions. The stability of foundation should be checked for the following aspects: (a)
Check for Bearing Capacity
The total downward load at the base of footing consists of compression per leg derived from the tower design, buoyant weight of concrete below ground level (i.e .. difference in the weight of concrete and soli) and weight of concrete above ground level. ' While calculating over weight of concrete for checking bearing capacity of soil, the pOSition of water table should be considered at critical location i.e .. which would give maximum over weight of concrete. In case of foundation with· chimney battered along the slope of leg, the centre line of chimney may not coincide with the C.G. of the base slabs/ pyramid I block. Under such situation, oxlal load in the chimney can be resolved into vertical and horizontal components at the top of base
29
slab/pyramid/block. The additional moments due to the above horizontal loads should be considered while checking the bearing capacity of soli. Further, even In cases where full horizontal shear Is balanced by the passive pressure of soli. the horizontal shears would cause moment at the base of footing as the line of action of side thrusts (horizontal shears) and resultant of passive pressure of soil are not In the same line. It may be noted that passive pressure of soil is reactive force from the soil for balancing the external horizontal forces and as such mobilized passive pressure In soil adjoining the footing can not be more than the external horizontal shear. Thus. the maximum soil pressure below the base of the foundation (Toe pressure) will depend upon the vertical thrust (compression load) on the footing and the moments at the base level due to the horizontal shears and other eccentric loadings. Under the action of down thrust and moments, the soli pressure below the footing will not be uniform and the maximum toe pressure 'P' on the soli can be determined from the equation:
W
MT
ML
P=-+ - + BxB ZT ZL
Where. 'W' is the total vertical down thrust including over weight of the footing; 'B' is dimension of the footing base; MT & ML are. moments at the base of footing about transverse and longitudinal axes of footing; and ZT & ZL are the section modulii of footing which are equal to (1/6) B3 for a sqlJare footing. The above equation is not valid when minimum pressure under the footing becomes negative. The maximum pressure on the soil so obtained should not exceed the limit bearing capacity of the soil. (b)
Check for Uplift Resistance
In the case of spread foundations, the re.sistance to uplift is considered to be provided by the buoyant weight of the foundation ,and the weight of the soli volume contained In the inverted frustum of cone on the base of the footing with sides making an angle equal to the angle of earth frustum applicable for a particular type of the soil. Referring to Figure 13. the ultimate resistance to uplift is given by : UP :: Ws + Wf where 'Ws' is the weight of soil in the frustum of cone; (The method of calculation of Ws is given in Annexure-V). 'Wf' is the buoyant weight/overload of the foundation (Refer Figures 13 & 14). Depending upon the type of foundation i.e .• whether dry or wet or partially submerged or fully submerged, the weights 'Ws' and 'Wf' should be calculated taking Into accounUhe location of ground water table. Under-cut type of foundation offers greater resistance to uplift than an Identical footing without under-cut. This Is for the simple reason that the angle of earth frustum originates from the toe of the under-cut and there Is perfect bond between concrete and the soli surrounding It and there Is no n~d to depend on the behaviour of backfilled earth. Substantial additional uplift resistance Is developed, due. to use of under-cut type of foundation. However. to reflect advantage of additional uplift resistance In the design the density of soil for under-cut foundation has been increased as given in Annexure -I.
In cases wnere HU:;IUIII VI C:UIItI I-IYIUIIIIU \:7 '-\:7- __ ,-_ .... -,--_ frustum Is assumed truncated by a vertical plane passing through the centre line of the tower base. VI
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Check for Side Thrust
(c)
In towers with inclined stub angles and having diagonal bracing at the lowest panel point. the net shearing force of the footing is equal to the horizontal component of the force in the diagonal bracing whereas in towers with vertical footings. the total horizontal load on the tower is divided equally between the number of legs. The shear force causes bending stresses in the unsupported length of the stub angle as well as in the chimney and tends to overtum the foundation. When acted upon by a lateral load. the chimney will act as a cantilever beam free at the top and fixed at the base anq supported by 'the soil along it's height. Analysis of such foundations and design of the chimney for bending moments combined with down thrust/uplift Is very important. Stability of a footing under a lateral load depends on the amount of passive pressure mobilized in the adjoining soil as well as the structural strength of the footing in transmitting the load to the soil (Refer Figure 12),
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I
\
I
\
/
\ \ \ \ \
I
/ / /
-.
\
\~ \~f
A
2
/
.&;
/ I
/
m
/ I
\
. ~.
B
-I PLAN 'A-A'
ELEVATION
Figure.14
(d)
Check for Over-Turning
Stability of the foundation against overturning under the combined action of uplift and horizontal shears may be checked by the following criteria as shown in Figure 14 :
0) (II) Oii)
The foundation over-turns at the toe. The weight of the footing acts at the centre of the base; and Mainly that part of the earth cone which stands over the heel causes the stabilising moment. However, for design purpose, this may be taken equal to half the weight of the cone of earth acting on the base, It is assumed to act through the tip of the heel.
For stability of foundation against overturning, stabilising moment should be more than overtuming moment. (e)
Check for Sliding
In the foundations of transmission towers, the horizontal shear is comparatively small and possibility of sliding is generally negligible. However, resistance to sliding Is evaluated assuming that passive earth pressure conditions are developed on a vertical projections above the toe of foundation. The friction between bottom of the footing and soil also resist the sliding of footing and can be considered in the stability of foundation against sliding. The coefficient of friction between concrete and soil can be considered between 0.2 to 0.3. However, the frictional force is directly proportional to vertical downward load and as slJch may not exist under uplift condition. For cohesive soil the following formula can be applied for calculating the passive pr~ssure to resist sliding: P =2 C tane + rh Ta~29 Where C
e
h
y. (2)
= = = =.
Cohesion (2t/m2 min.) 45° + 1/2 of angle of earth frustum Height of foundation Unit Wt.of soil
Structural Design of Foundation
Structural design of concrete foundation comprises the design of chimney and the design of base slab/pyramid/block. The structurql design of different elements of concrete foundation is discussed In the following paras: (a)
Structural Design of Chimney
The chimney should be deSigned for maximum bending moments, due to side thrust In both transverse and longitudinal direction combined with direct pull (Tension) / direct down thrust (Compression). Usually, combined uplift and bending will determine the requirement of longitudinal reinforcement In the chimney. When stub angle is embedded in the chimney to Its full depth and anchored to the bottom slab/pyramid/block, the chimney is designed. Considering passive resistance of soil leaving 500 milimetres from ground level. This is applicable for all soils - cohesive, non-coheslve and mixture of cohesive and non-cohesive soils. In hilly areas and for fissured rock, passive resistance of solis will not be considered. Stub angle will not be considered to provide any reinforcement. In certain cases, when stub is embedded in the chimney for the required development length alone and same is not taken upto the bottom of foundation or leg of the tower is fixed at the top of the chimney /pedestal by anchor bolts, chimney should be designed by providing 'reinforcement to
33
withstand combined stresses due to direct tension (tension)/down thrust (compression) and bending moments, due to side thrust in both transverse and longitudinal direction. The structural design of chimney for the above cases should comply with the procedures given in IS: 456-1978 and SP: 16 using limit state method of design except as specifically provided In this document.
CASE-I:
WHEN SlUB ANGLE IS ANCHORED IN BASE SLAB/PYRAMID/BLOCK
When the stub is anchored in base slab/pyramid/block reinforcement shall be provided in chimney for structural safety on the sides of the chimney at the periphery. From the equilibrium of internal and external forces on the chimney section and using stress and strains of concrete and steel as per IS:456, the following equations as given In SP: 16 are applicable. n
Pu =O.36k+!; (Di/lOO) (Fsi-Fci) + (pS/100) (Fss-Fcs)/Fck ... (1) 2 FckB3 1-11 m~ I m = modular ratio . . --I
IK = M
i
. =O.36k(O.5-0.416k) FckB3 2 i-
I
- - ; c cbc cs:t. + ~ ~ _c st ____
+1:
=permissible bending com.press stress in =permissible len~!~ str~_s.~n!~eel_________.=--~.
(pi/100) (Fsi-Fci)/Fck) (YijD)
... (,,)
i-1
D:-Total deptll of stub:
Where Asi pi .Fci Fsi
= = = =
Vi
=
n Fss Fcs Fck
= = = =
Cross-sectional area of reinforcement In ith row 100 Asi/B3 2 Stress in concrete at the level of ith row of reinforcement Stress in the ith row of reinforcement., Compression being positive and tension being negative distance from the centroid of the section to the i'h row of reinforcement; positive towards the highly compressed edge and negative towards the least compressed edge Number of rows of reinforcement Stress in stubs Stress in concrete Characteristic compressive strength of concrete
CASE-jl: WHEN SlUB IS PROVIDED IN CHIMNEY ONLY FOR ITS DEVELOPMENT LENGTH· When stub is provided in chimney only for it's development length, chimney has to be designed for and reinforcement provided for combined stresses due to direct pull(tension)lThrust (compression) and bending moments. The requirement of longitudinal reinforcement should be calculated in accordance with IS: 456 and SP: 16 as an independent concrete column. In this case, from the equilibrium of internal and external forces on the chimney section and using stress and strains-of concrete and steel as per IS:456, the following equations as given in SP: 16 are applicable. n
Pu 2 =O.36k(O.5-0.416k) FckB3
+L
(pi/100) (Fsi-FCi)/Fck)
...
(~)
i-1
In each of the above cases, for a given axial force, compression or tension, and for area of
n
E
Mu 2 =0.36 k (0.5 -0.416 K) + (pi/100) (Fsi-Fci) / Fck) (Yi/D) FckB3 i"'l
...
(~.
reinforcement. the depth of neutral axis Xu=kB3 can be calculated from equation (1) or (3) using stress strain relationship for concrete and steel as given In IS: 456-1978. After finding out the value of 'k' the bending'capacity of the chimney section can be worked out using equation (2) or (4). 'The bending capacity of the chimney section should be more than the maximum moment caused In the chimney by side thrust (horizontal shear). Chimney is subjected to biaxial moments i.e., both longitudinal and transverse. The structural adequacy of the chimney in combined stresses due to axial force (tension/compression) and bending should be checked from the following equation: \
< 1,0 \,
Where, MT and ML are the moments about transverse and longitudinal axis of the chimney: Mut and Mul are the respective moment of Resistance with axial loads of Pu about transverse and longitudinal axes of chimney which would be equal In case of square chimney with uniform distribution of reinforcement on all four faces:
_nPu/Puz is an exponent whose value would be 1.0 when axial force is tensile and depends on the value of when axial force is compressive where: Puz = 0.45 Fck Ac + 0.75 Fy As + 0.75 Fys Ass In the above equation, Ac is the area of concrete; As is the area of reinforcement steel; Ass is the cross sectional area of stub, to be taken as zero; Fy is the yield stress of reinforcement steel: and Fys is the yield stress of stub steel, to be taken as zero. Pu/Puz
n
0.2 0.8
2.0
1.0
For intermediate values. linear interpolation may be done. The solution of equations (3) & (4) for case-2 Is given In SP-16 in the form of graphs for various grades of concrete and steel and these can be readily used. IMPORTANT CODAL STIPULATIONS FOR STRUCTURAL DETAILING OF CHIMNEY
While designing the chimney. the important codal provisions as given below should be followed: (a)
In any chimney that has a larger cross-sectional area than that required to support the load. the minimum percentage of steel shall be based on the area of concrete required to resist the
35
direct stress and not on the actual area. (b)
The minimum number of longitudinal bars provided in a column shall be four in square chimney and six in a circular chimney.
(c)
The bars shall not be less than 12 mm in diameter.
(d)
In case of a chimney in which the longitudinal reinforcement is not required in strength calculations, nominal longitudinal reinforcement not less than 0.15% of the cross sectional area shall be provided.
(e)
The spacing of stirrups/ lateral ties shall be not more than the least of the following distances: (1) (2) (3)
The least lateral dimension of the chimney Sixteen times the smallest diameter of the longitudinal reinforcement bar to be tied Forty-eight times the diameter of the transverse stirrups/lateral ties.
(f)
The diameter of the polygonal links or lateral ties shall be not less than one-fourth of the diameter of the largest longitudinal bar, and in no case less than 6 mm.
(g)
Structural Design of Base Slab
The base slab in R.C.C. Spread foundations could be single stepped or multi stepped. The design of concrete foundations shall be done as per limit state method of design given in IS : 456 - 1978.
IMPORTANT CODAL STIPULATIONS FOR R.C.C. FOUNDATIONS The important provisions applicable for concrete foundations which are necessary and should be considered in the design are explained below: (a)
Footings shall be designed to sustain the applied loads, moments and forces and the induced reactions and to ensure that any settlement which may occur shall be as nearly uniform possible, and the bearing capacity of the soil is not exceeded.
(b)
Thickness at the edge of footing in reinforced concrete footings shall be not less than 15 cm (5 cm lean concrete plus 10 cm structural concrete). In case of plain concrete footing, thickness at the edge shall not be less than 5 cm).
(c)
Bending Moment (i)
The bending moment at any section shall be determined by passing through the section of a vertical plane which extends completely across the footing, and computing the moment of the forces acting over the entire area of the footing on the side of the said plane.
(ii)
The greatest bending moment to be used in the design of an isolated concrete footing which supports a column/pedestal shall be the moment computed in the manner prescribed in c(i) above at sections located as follows : (1) (2)
(d)
At the face of the chimney; At sections where width/thickness of the footing changes.
Shear and Bond
The shear strength of footing Is govemed by the more severe of the following two conditions:
(e)
(1)
The footing acting essentially as a wide beam. with a potential diagonal crack extending in a place across the entire width; the critical section for this condition shall be assumed as a vertical section located from the face of the chimney at a distance equal to the effective depth of the footing in case of footings on soils;
(2)
Two-way action of the footing. wHh potential diagonal cracking along the surface of truncated cone or pyramid around the concentrated load;
Critical Section
The critical section for checking the development length in a footing shall be assumed at the same planes as those described for bending moment In para (c) above and also at all other vertical plahes where abrupt changes of section occur. STRUCTURAL DESIGN OF BASE StAB SHALL BE DONE AS PER THE PROVISION OF E-1 OF APPENDIX-E-'OF IS: 456-1978.
When a plain concrete pyramid and chimney type footing Is provided and pyramid slopes out from the chimney at an angle less than 45° from vertical. the pyramid Is not required to be checked for bending stresses. Thus. in such cases. the footing Is designed to restrict the spread of concrete pyramid of slab block to 45° with respect to vertical. 10.11
CONCRETE TECHNOLOGY FOR TOWER FOUNDATION DESIGNS
While designing the various types of concrete footings. it is better to know about certain aspects. of co~crete technology which are given below: (a)
Properties of Concrete
The grade of the structural concrete used for tower foundations should not be leaner than M-15 (1 :2:4) having a 28-day cube strength of not less than 15 N/mm2 and concrete shall confolm to IS: 456. For special foundations like pile foundations. richer concrete of grade of M 20 (1: 1.5:3) having a 28-day cube strength of not less than 20 N/mrrt should be used. M-15 grade concrete shall have the nominal strength of not less than 15 N/mm2 at the end of 28 days as ascertained form the cube te.st. Such strength at the end of 7 days shall not be less than 10 N/mm2. The density of the concrete will be 2300 kg/m 3 for plain concrete and 2400 kg/m 3 for R.C.C. Oth.er· properties of concrete are given In IS: 456. (b)
Properties of Steel
The high yield stress cold deformed reinforcement bars used in the R.C.C. shall conform to IS: 1786-1979 and shall have yield stress of not less than 415 N/mm2. When mild steel reinforcement bars are used in R.C.C.. they shall conform to IS: 432 (part - I) and shall have yield stress of not less 26 N/mm2 for bars of size upto 20 mm diameter and 24 N/mm2 for bars above 20 mm diameter. 10.12
PULL-OUT TESTS ON TOWER FOUNDATION
The pull-out tests conducted on foundations help In determining the behaviour of the soil while resisting . the up-lift forces. The feed back from this pull-out test results. In a particular type of soli. can be conveniently used In the
37
designs of foundations. The procedure of pull-out tests, equipments and results are discussed In detaU below: (0)
Selection of Site
Trial pits of size 1.Ox1.0x3.0(d) metre are mode and the strata of the soil Is observed. It is ascertained that the strata available at the location Is one In which we are Interested (I.e., a particular type of soil or combination of soils is available). Soil samples are takEm from and around the'slte and subjected to various tests, particularly relating to the density of soli, bearing capacity of soli, cohesion and angle of intemal friction etc. (b)
Design of Foundation for Pull-Out Test
Design of foundations for pull-out test is carried out with a different view point os compared to the design of actual foundations for tower. this Is due to the fact that the pull-out tests are conducted to measure the pull-out resistance of the solis and therefore all the other ports of the foundation viz concrete, reinforcement and the pull-out bars should be strong so that these do not fall before the soli/rock fails. Based on the actual tower foundation loadings (down thrust, uplift and side thrust) and the soil parameters obtained from the tests, a foundation design is developed. The design has a central rod running from the bottom of the footing upto a height of about 1.5 m to 2.0 m above ground, depending on the jacking requirements. The central rod is surrounded by a cage of reinforcement bars. A typical design developed for the pull-out test is shown in Figure 15.
30_O -r--_ _
G.l.
±_ =-1
Pull-out bar
300
GoL.
<:) <:)
.... 11\
~ 1S~
I.
1100
ELEVATION
Figure - 15
(c)
Casting of Foundation
The pits are ~xcavated accurately. The concrete mix, reinforcement form boxes etc., are exactly as per the design. The pouring ofthe concrete is don,e such that voids are minimised. The back filling of the soil should be carried out using sufficient water to eliminate voids and loose pockets. The foundation should be cured for 14 days (minimum) and thereafter left undisturbed for a period not less than 30 days. (d)
Pull-Out Test Set-Up
As indicated earlier, the pull-out is done with the help of central hole jacks of different capacities (10 M.T. to 100 M.l). Each & every test foundation, therefore, has a central pulling bar. The schematic diagram of the test set up is shown In Figure 16.
:c:: I I
I I
I~ .
\ \
1\ )I~
\
\
~I ~ I "-
' ~ • ~ "
"+__ J _'"
\L \ ,_ ' _ _L
~-
/
I I
I
\
I:l:lI
- -1----
Figure - 16
39
9
The foundation under test (1) is below the ground level. The central pulling rod (12) is projecting out of the ground to the specified height. Sets of sleepers (2) are placed on either side, away from the likely pull-out region through angle (9) A set of two girders (8) is placed on the sleepers. The central hole jack (4) is kept on these girders covering the pull-out bar in it's hollow. Two dial gauges (3) capable of sensing a movement of 1/1 ClOth of.mm are used to record movements of the jacks and the soli. The dial gauge to measure movement of the jack is kept just touching the top of the pull-out bar by means of a pair of stands (10) and a datum bar (11). The dial gauge on the ground is kept just touching the soil surrounding the top of the foundation by means of a stand (14). Hydraulic oil is pumped In to the jack by a hydraulic pump (5) by moving the handle (13). The pressure built up in the jack is recorded by the dynamometer, (6) on the top of the pump. The upward movement of the jack is prevented by two nuts (7) on the top of the threaded portion of the central pulling bar. This develops upward load on the foundation. The oil is pumped gradually in10 the jack and readings of the pressure gauge and dial gauges are taken at intervals of 500 Kg to 1000 Kg depending upon the estimated uplift resistances. In the beginning, the dial gauges will not have appreciable movement but as the load increases, movement will be significant. The movement of the soil surrrounding the foundation will be visible as soon as the foundation starts yielding. At a particular juncture, the load will not show any increment and Instead undergo a decrement. This juncture will be the final yield load of the soil surrounding the foundation. The jack can be unloaded by opening the outlet in the pump and operating the lever so that the pressure is released gradually. The curves of load versus dial gauge movements are plotted and the size and the shapes of crack developed at the top of the soil are also recorded as shown in Figure 17. 60 50
> ..x
40 A
c 30
-go 20
.J
10
V
oV o
V
V
~
.-
'" ..... I'B
234567
Deformation in mm
Top of foundation
Pulling bar
"'Cracks on the soil
PLAN Figure .17
It may be noted that the deformation of foundation is recorded by the dial gauge kept on the top of the pull out bar. where as the deformation of ground is recorded by the dial gauge kept on the ground. (e)
Comparison of Design and PUll-Out Test Results
The ultimate pull-out resistance offered by the foundation is later compared with the parameter assumed in the design. proper analysis of the test is done and inference drawn regarding the actual soil parameters. 10:13
SKIN FRICTION TESTS
To determine the contact skin friction of soil and the concrete. this test is very important. Small pits in the undisturbed layers of soil are made. The dimensions generally used are 300x3OOx300 MM. 300x300x600 MM. 300 (dia)x3oo MM (depth). 300 MM (dia)x600 MM (depth). These configurations are shown in Figure 18. The concrete is poured directly in contact with the soil. For pulling. a central rod and a cage is provided. The pUll-out tests are done just as described in 10.12. The ultimate failure load On kg) after deducting the self weight of the foundation Is divided by the area of surfaces In contact with the soli On sq cm). This result is the ultimate skin friction In kg/cm2• The data obtained from the skin friction tests have been found very reliable and have also been covered in the recommended parameters by some utilities. The skin friction test results are very useful in designing foundations for rocky and non-cohesive soils (like soft and hard murrum) The average skin friction value recorded during test on some of th soils are given below: .
0) Oi) Oii) (iv) (v)
(vi)
Normal yellow dry soil Black cotton dry soli Soft murrum soil Hard murrum soil Soft rock Hard rock
-
0.3 kg/cm2 (ultimate) 0.1 kg/cm2 1.0 kg/cm2 2.0 kg/cm2 3.0 kg/cm2 4.5 kg/cm 2
It should be noted with care that the skin friction values are applicable only in cases where foundation concrete is poured directly in contact with soil or rock. 10.14
SCALE DOWN MODELS OF FOUNDATION
The pull-out tests can also be done on various scale down configuration in different types of soils. These are shown in Figure 19. The advantages of this type of pull-out test are low cost and less time per test and quick comparison between the models. The disadvantage is that the exact behaviour of the soli can not be determined if the exploration is carried out in the top layers of soil upto a depth less than 1500 mm. The pull-out tests done with these configuration under dry and wet conditions have revealed that the stumps drlven foundation offer extra 15% uplift resistance. and undercut type foundation offer extra 50% up-11ft resistance. as compared to the friction type foundation. In case of stumps driven foundations. the stumps of steel rods In contact with the soil may get corroded In the long run and the advantage of 15% may not be available. However, these will be able to contribute In counteracting the stringing/construction load on foundations and thus may afford early tower erection and stringing.
41
---....,o o
rt>
PLAN
\_ 300;
_I
~300 ~ ELEVATION
o o..., PLAN
o
g 300 ELEVATION
Figure. 18 10.15 TESTS ON SUBMERGED SOILS It is very difficult to carry out pull-out tests on naturally submerged soil as the testing gadgets are likely to sink in the mud when pressure is increased In the hydraulic jack. Besides, It is also difficult to regulate the sub-soil water. The tests on these types of soils can be conducted by creating similar conditions in an underground runriA of nridl mmonrv dulv olastered form inside). The soil to be tested (i.e., normal, black
",non ""l'Y'In
G.l. o
o
~
o
o or "
o
an ,.,.. o
an
N
1000
.1~
PLAN
ELEVATION
PLAN
ELEVATION
_____________ ,.
150 1 '
l
rOOi
1 I
:
,
1 0 L'
!
o o
1
111 ,.,..
!gf I~
g : ~
G.l.
, , 1
1
~
o
I
.
1 ,I
T"- --~LA~- ----"
1501.,'..
1000 ElEVA TlON
Figure - 19
43
cotton, marshy etc.) is borrowed form elsewhere and dumped in the part of the sump/tank and is well compacted. Three to four cycles of dry and wet spells are given to the soil till It attains the density of the dry parent soil. The typical arrangement of this test is shown In Figure 20.
Pull-out Set-u
I' .......... ,
I .,
.
,.
". '~"',1 :. . ~ .: J • '. \
1,-"
,./-::,
l: Ii",:.. ,:
• I
• '.
. ,.',
r ' :.' '::'.
I
\'
,
I
", . ".---t---.. .....
...
f
•
'
•
"
...
'
"
'.
......
oundation under test orrowed soil
"
I'
"
••
:., .. ,',. '.' : :',':": ':..' ".:;: ~::
asonary tank
.' .,> :'., .. . ..,:.:,.'.:. : '.:. ::r.;;'·::;;:·+F+-Harrier ..
'
.',' ..
Figure. 20 Four 50 mm dia pipes are placed in the four corners of the tank vertically before dumping the parent soiL In 'such a way that their both ends remain open for the passage of water. The foundation is cast on the partially filled soil. The remainder of the tank is then fully filled with the some type of borrowed soli. This soli is again well compacted and three to four cycles of wet and dry spell are given.The wetness is created using the pipes. The pull-out tests is conducted by keeping the gadgets on the ground level with the some process as Indicated in 10.12 under the presence of sub-soil water pressure created through the extemal watering of the tanks using the pipes. 10.16
INVESTIGATION OF FOUNDATION OF TOWERS
Normally it is believed that once the foundation is cast and the tower is erected, the foundations can not be re-opene.d for investigation or repairing. However, on the basis of investigation and rectification work carried out on some major 220 kV and 400 kV lines, it is now conSidered to be viable to carry out this type of exercise even after the line Is strung and energised. If the foundations on the line have to be investigated, certain locations are selected at randum in such a fashion that foundations for various types of soils are covered one by one. One or two locations for every ten km may be sufficient for preliminary investigations. Out of the four individual footings of selected tower, two diagonally opposite foundations are selected and one of the four faces of each of these two foundations is excavated in slanting direction from top to bottom. This is shown in Figure 21. After the investigation is over and corrective measures have been chalked out it is advisable to backfill the excavation mixing earth with light cement slurry, particularly when the soil is non-cohesive such as soft murrum/hard murrum, softrock/hard rock etc., (say one cement bag for every three to four cu m of earth). This will ensure good bond and safeguard the foundation against uplift forces, even if corrective repairs of the foundations are delayed.
!
..
Direction of Tr. Line
'-'-i-'-'0 A.B.C.D. Footin95 I of Tower Ope n'ed face I .
~
__ .--.£:..L.
ofl Tow~~. __ Opened face
~.-.-t--. PLAN G.L.
Bottom of foundation
Figure. 21 10.17
SECTION
INVESTIGATION OF FOUNDAnON OF A TOWER UNE IN SERVICE
For the investigation of failures of foundations or for the investigation of reported unhealthy foundations, with line in service, the excavation at the selected location Is carried out In the same fashion as described in 10.16. However. the line being In service, it will be better to guy the comer leg/legs of the tower (on which the Investigation Is being carried out) at 45° diagonally from top, a.Noy from the induction zone. The investigation and the back filling should be done exactly as detailed In 10.16. 10.18
REPAIRS OF FOUNDATIONS OF A TOWER UNE IN SERVICE
After It is establised that the foundation is unhealthy, it is better to take the corrective steps as early as possible. The methods would be cliffe rent for rectifying Isolated location/locations (or:le to two) and for rectifying complete line/line sections Including a number of towers. These are discussed below: (a)
Rectification of isolated locations (one or two) Is done on individual basis. Anyone of the four footings is taken up first. It is opened up from all the four sides. The tower legs connected to
45
this footing are guyed as described in 10.17. After rectifying the foundation backfilling is done as described in 10.16. A minimum of seven-days' time is allowed for curing of the repaired foundation before excavating the second leg for repairs. All the four legs are repaired thus without any outage on the line. (b)
When foundation rectification work is required to be done on a complete line or line section without any outage, a section from cut point to cut point is selected. The four footings of each tower in the section are named 'A', 'B', 'C' and 'D' clock-wise as shown Figure 22.
-§--._. ._.---Q ~.B.C.D. Tower legs
. Direction of 'line
-$:-.-. .-.-=$Figure. 22 The excavation of leg 'A' in first location, 'B' in second location, 'c' in third location and 'D' In fourth location can be taken up first. This order can be continued for each group of four towers in the section. After excavation, rectification and backfilling, seven days curing time Is be allowed. Again from location 1 to 4, the excavation rectification and backfilling is done In the sequence leg 'c', 'D', 'A' & 'B'. This Is repeated for each group of four towers of the line section under repairs. After passage of 7 days again the sequence 'B', 'c', 'D' & 'A' and again after 7 days the sequence '0', 'A', 'B' & 'c' are repeated for each group of four towers. This exercise.can be repeated for each group of four towers for the remainder of the line section. All the precautions described earlier should be taken during this exercise. It is advisable to avoid this exercise during abnormal wind conditions/active monsoon/ flood etc. If the work is to be completed early, two diagonally opposite footing of each towers can be opened and repaired simultaneously. The second pair of diagonally opposite footings can be opened and repaired simultaneously atter a passage of seven days. 10.19
FOUNDATION DEFECTS AND THEIR REPAIRS
The main possible defects In the cast concrete can be as follows : (a)
Under sizing of foundation due to wrong classification of soil: For example, the soil may be dry black cotton but the foundation cast may be that for normal dry soil. If the corrective measures are not taken, the foundation can fail. An R. C.C. collar is designed for the type of soli and tower loadings to remedy such a defect. The details are shown in Figure 23.
(b)
Improper formation of pyramid/chimney etc. due to improper concrete laying: If the concrete is simply poured from the top of the form box, without taking care to fill the voids (using crow bar, vibrator etc.) the concrete does not reach to the comers of the form and thus the foundation is not compfetely formed. It will develop the defects described below.
..'
, ,
I I I I I
, I
I
",
/1.1
'I'
r-.J
1/ :
I
" I
I
G.L.
el,i ~~~~~~-,,/1 ,Existing under size '~1'f ,' foundation 1/ , I
,
I
L -.,....- Proposed I steps for
~-l
C¥J
... _-J I I
I
.
R.Le. collar in reinforcement
.Figure - 23 As seen in Figure 24, the foundations have not attained the required shapes In the pyramid, undercut and chimney portions. These defects can be rectified with R.C.C. collars. The design of the collars will depend upon the requirement of the load transfer (I.e., thrust. uplift and side thrust) and extent of deformation of the foundation.
Stub
(i.i..
, , ., ,, , ~', , 1,.1 : ,"'~' , , ~/, , I!
(i.L
',' , fil
,.,1/1
c.f-:J
Actual shape
of pyrHlid
47
(c)
Damage to stub top and top part of the chimney: Due to ingress of saline water or other chemical pollutants etc. the stub top part of the steel in the chimney gets corroded. Repairing can be done by welding the damged portion of the stub and providing R.C.C. collar to the damaged chimney top as shown in Figure 25. For providing a welded joint. the part of the cast concrete in the top part of the chimney is broken. All the precautions indicated in 10.16 must be taken to safeguard the line in service.
ANNEXURE ·1 Soli Properties to be considered In Foundation Designs for various types of SoIl SI. No.
1.
Type of Soil
Normal Dry Soil (a) Without Undercut (b) With undercut
Angle of Earth frustum (Degree)s)
Unit wt. of Soil (kg/cu m)
Limit bearing capacity (kg/sq m)
30 30
1440 1600
25.000 25.000
15
940
12.500
2.
Wet Soil due to presence of sub soil water/surface water
3.
Black Cotton Soil (a) In Dry Portion (b) In Wet Portion
0 0
1440 940
12.500 12.500
Sandy Soil (a) With Clay Content
10
1440
25.000
20 -
1440
25.000
20' 10
1700 940
62.500 . 62.500
4.
I
r
1
0-5% (b) With Clay Content
5-10% 5.
Fissured Rock/Soft Rock (With Undercut) (a) In Dry Portion (b) In Wet Portion
6.
Hard Rock
--
--
1.25.000
7.
Normal Hard Dry Soil (Murrum) with Undercut
30
1600
40.000
Note: ... 1. limit bearing capacity of soil has been arrived at taking FOS 2.5 over the safe bearing capacity values. Soil research institutes will be approached to furnish the limit bearing capacities of soli. If and when such data are available the above values can be reviewed. 2. Where clay content is more than 10% but less than 15%. the soil will be classified as Normal Dry Soil. 3. Angle of Earth Frustum shall be taken with respect to vertical.
49
ANNEXURE • II
Ust of SoIls Tests (A)
To find out the soil properties, the following laboratory tests shall be carried out : (1) (2) (3) (4) (5) (6) (7)
Grain size distribution/sieve analysis to Identify the type of soli Atterburg limits (liquid and plastic limits only) Specific gravity, bulk unit weight moisture content Triaxial shear test for coheslon(c) and angle of Internal friction (+) Consolidation test Standard penetration test Chemical test on soil and water (only at special locations such as marshy soils, chemically active soils etc.) to determine the carbonates, sulphates, nitrates, organic matters and any other chemicals harmful to the concrete foundations.
(8)
The above tests shall be useful in determining the types of soil, density, limit bearing capacity etc. For determining the angle of earth frustum 2/3rd value of angle of internal friction (+) or the values given in Annexure-I whichever Is smaller shall be taken.
(C)
Standard penetration tests shall be conducted at depths as follows :
(i) ~i)
Location
Depth (m)
Normal Locations River crossing & special Locations
1.5. 3.0. 4.5, 7.00 1.5. 3.0, 4.5. 7.00. 10.00 & thereafter at the rate of 3 M inteNals upto 40 M.
Bore hole logs shall be prepared for the locations where above tests have been conducted. (D)
During execution. trial pits upto a minimum depth of 3.0 m (except rocky locations) shall be excavated at each and every tower locations ( at all four legs) to obtain following details in order to classify the type of foundation to be adopted : 1)
Type of soli encountered
2)
Ground Water table.
ANNEXURE ·111 Guidelines for classification of Foundations In different Soh 51. No.
Type of soil encountered
Type of foundation to be adopted
1
In good soli ( silty sand mixed with clay)
Normal Dry
2
Where top layer of Black Cotton soil extends upto 50% of the depth with good soli there after
Partial Black Cotton
3
Where top layer of black cotton soli exceeds 50% and extends upto full depth or Is fol!owed by good soil
Black Cotton
4,
Where top layer is good soil upto 50% of the depth but the lower layer Is a black cotton soil.
Black Cotton
5
Where subsoil water Is met at 1.5 m or more below the ground level In good soil
Wet
6
Good soil locations which are In surface water for long period with water penetration not exceeding 1.0 m below ground level (e.g., paddy fields)
Wet
7
In good soil where subsoil water Is encountered between 0.75 m and 1.5 m depth from ground level
Partially submerged
8
In good soli where subsoil water Is encountered within 0.75 m depth from ground level
Fully Submerged
9
Where top layer of normal dry soli extends upt6 85% of the depth followed by fissured rock without presence of water
Dry Assured Rock
10
Where top layer Is fissured rock followed by good soli/sandy soli with/without presence of water
Special foundation
11
Where normal soil/fissured rock extends upto 85% of the depth followed by hard rock
Dry fissured Rock with under cut In FIssured Rock combined with anchor bar for hard.rock design.
12
Where fissured rock is encountered with subsoil water within 0.75 m or below 0.75 m from G.l. (Top layer may be either a good soli or black cotton soil)
Submerged Assured Rock
13
Where Hard Rock is encountered at 1.5 m or less below ground level
Hard Rock
14
Where Hard Rock is encountered from 1.5 m to 2.5 m below G.l. (Top layer being good soli)
Hard Rock Foundation with chimne~ for Normal Soil
51
15
Where hard rock is encountered from 1.5 m to 2.5 m below G.L. (Top layer either in Black cotton soil or fissured Rock)
Hard Rock Foundation geslgn with c~im..ne.'£.s geslgne_Q for wet bla~ ~ottQO~Qib--
16
Where fissured rock Is encountered at the bottom of pit (with black cotton soil at top)
Composite Foundation
17
Where hard rock is encountered at bottom with water and black cotton soil at top and hard rock layer depth is less than 1.5 m
Hard Rock
18
Sandy soil with clay content not exceeding 10%
Dry Sandy soli foundation
19
Sandy soil with water table in the pits
Wet sandy soli design to be developed considering the depth of water
20
Where top layer upt6 1.5 m below G.L. is normal dry soil and thereafter hard soil/murrum
Normal dry with undercut
21
Where bottom layer is marshy soH with top loyer of good soil/fissured rock/ black cotton
Soil Investigation is to be carried out and special foundation design to be developed
22
Where the top layers are a combination of clinker mixed with firm soil. gravel and stone chips upto Wfo of foundation depth from ground level followed by Hard murrum
Normal dry with undercut
23
Where top layers are combination of hard murrum. soft rock etc. followed by yellow/black clayee soil
Special foundation design is to be developed after carrying out soil Investigation
Any other combination of .soil not covered above sholl require development of special foundation design.
ANNEXURE - IV
Bond Stresses (1)
Limit415 Bond Stress between Concrete and reinforcement steel deformed bars In tension of grade Fe: Conforming to IS: 1786-1985 or IS: 1139-1966
(a)
(2)
As per IS: 456
(b)
With M:15 Mix With M:20 Mix
Note:
For bars in compression the above values shall be increased by 25%
16 kg/cm2 19.5 kg/cm2
/
Limit Bond Stress between Concrete and Stubs in Tension with (a)
(b)
M:15 Mix M:20 Mix
10 kg/cm 2 ./ 12 kg/cm 2
For compression the above values will be increased by 25% (3)
Limit band stress between Rock and Concrete (a)
(b) (4)
In Fissured Rock In Hard Rock
1.5 kg/cm2 4.0 kg/cm'" ./
Limit bond stress between hard rock and grout 2.0 kg/cm2
53
.f
ANNEXURE· V
'i
~1·_------=.B------1·1
Where oc
,~ are
respective angle of earth frustum B: bose width . - - - - -_ _ _ _ _ _ _ _-.;of footing.
-
,'-------------------The Formula for Calculating the Volume of Conical Pyramid Frustum' of Soi I . VOL. OF. UPPER PORTION OF SOIL /-\
A, . = ~
=
2 8 + 4 x 8 xH l TANot+ 7t x ~}AN2o(. 2 8 + 4 x 8 X (H l TAN 0(..+ HuTAN P) + 7t (H l TAN 0(.+ Hu TAN~)2
3
[
A,+A,+~A,A, 1
VOLUME OF LOWER PORTION OF SOIL 2 VL = 8 X H, + 2 x 8 X H,2 TAN rL+ ~ x 7t
X
H.] X TAN1,{
Typical Illustration for Examples of Design Calculation Illustration· ILLUSTRATION NO - I DATA
",
,
1.
400 KV D / C Transmission line
2.
Tower type: "DB"
3.
Design loads (Limiting/ultimate) (inclusive of overload fador 1.2)
4.
Description
Normal Condition (Reliability) (Kgs.) .
Broken Wire Condition (Security) (Kgs.)
Down thrust uplift side thrust (T) side thrust (L)
165598 140917 5907 825
154376 130185 8283 4983
Tower SIQpes:
TAN e= 0.192570 True length factor = 1.036 5.
J
Soil/rock data:
unit weight of dry soil~ 1440 kglcu.m unit weight of to wet soil=940 kg/cu.m unit weight of dry fissured rock=1700 kg/cu.m unit weight of wet fissured rock=940 kg/cu.m unit weight of hard rock=1440 kg/cu.m limit bearing capacity (dry locations) : 27350 kg/sq.m limit bearing capacity (wet locations) : 13675 kg/sq.m limit bearing capacity (fissured rock locations) : 62500 kg/sq.m limit bearing capacity (hard rock locations) : 125000 kg/sq.m ILLUSTRATION NO - " DESIGN OF WET TYPE FOUNDATION 1.0
Volume of Concrete (Cu.m.) :
=13471 =2.694/ = 6.106 =0.605 /
5.19 2 X0.050 5.19 2 X 0.100 0.25/3 {5.19 2 + 4.69 2 + 5.19 X 4.691 1.742 X 0.2 0.65 2 X2.625
1
= 1.109/
11.861
55
U'\
~ _~G=..L.;'-_"'"'TI'Tor--_ _m't"_ _ _-I
0 0
-.1' N
0 0 0
,.,...
I \
... --\.
0 0
N'
o
0.
......__ . . . "-~_~,t:::.:z!:.,::;.:::::&:=..=.:c.::..~.s::' . . ,;:.=:.::£:.::-=.
. . :z1
(All dimensions "~'-='j=:"!:\.::;.".~.==. I _I Lean concrete are in mm)
=.
I..
1740---'
(1:3:6)
1.....----4690----~ .. 1
-'1
......- - - - - - 5190 - - - - - - -..
Sketch 1: Wet Type Foundation NOTE: ALL DIMENSIONS IN THE SKETCH ARE IN MM.
2.0
Over Load of Concrete (kgs.) : Uplift
compression 0.65 2 X 0.225 x 2400 (11.861- 0.095) X (2400-1440) 0.65 2 X 1.5 X (2490-1440) (11.861-1.347 -.0095-0.634 X(1400-940)
-----
= = = =
228
228 11295
608 4501
~ ~\JfII'
11523
3.0
5337
Dry Soil Volume: (Cu.m) Al=5.19 2+4 X 5.19 X 0.362 + 3.14 X 0.3622 A2=5.19 2+4 X 5.19 X (0.866+0. 362) + 3.14 X (0.866+0.362)2 V = (1.5/3) [ 34.857+57.160 + V(34.857x57.160))
=
= =
34.857 57.160 68.327
.,.U
wer ~o" VOlume: (Cu.m)
5.19 2 X 1.45 5.19 X0.362 X 2 X 1.35 3.14/3 X 0.3622 X 1.35
=
39.057 5.069 0.185
= =
44.311
\
5.0
Check for Uplift
5.1
Resistance Against Uplift
= 68.327 x 1440 + 44.311 x 940 + 5337 F.G.S (NC)= 145380/140917 = 1.032> 1.0 F.G.S (BWC) = 145380/130185 = 1.120> 1.0
:
= 145380 kgs. Hence O.K.· Hence O.K.'
6.0
Moment due to Side Thrust at Foundation Toe
6.1
NORMAL CONDITION (TRANSVERSE SIDE THRUST) Side thrust force = (F) =1/2 x w x h2xB3 x 1+Sin ~ 1-Sin 4> Where W = 940 kglm3 ct> = Angle of Earth Frustum = 15° B3 = 0.65 1+Sin15° F = 1/2 x 940 x (hF x
x 0.65 1-Sin 15°
h = ..J (F/518.86) F1 = ST = 5907 Kgs . h =..J (5907/518.86) = 3.374m Since h therfore the soil pressure will only be mobilised in (2.4-0.5) i.e. 1.9m depth.
>§.4-0.5Ym
Resisting soil force F = 518.86x1.9 2= 1873.09 kg Moment due to side thrust at the base of the footing . = 5907x (2.95+0.225) - 1873.09x (O.55+r, .9/3) = 1653a.85 kg m / ' 6.2
NORMAL CONDITION (LONGITUDINAL SIDE THRUST) Side thrust force = (F) =1/2 x w x hx1ri x 1+Sin 4> 1-Sin 4> Where W = 940 kglm3 ~ = Angle of Earth Frustrum = 1S° B3 = 0.65m
57
1+Sin15° F = 1/2 x 940 x (hF x
x 0.65 1-Sin15°
h=..J (F518.86) F1= SL = 825 Kgs h =..J (825/518.86) = 1.261 m Since h < (2,4-0.5) m therfore the soil pressure will only be mobilised in 1.261 m depth from root of the chimney. . Resisting soil force F = 518.86x1.26 P= 825 kg
/
Moment due to side thrust at the base of the footing =825x(2.95+0.225) - 825x(0.55+ 1.261/3) = 1818.85 kg m
J
6.3
,/
BROKEN WIRE CONDITION (TRANSVERSE SIDE THRUST)
Side thrust force = (F) =1/2 x w x h2 xB3 x
1+Sin $ l-Sin $
Where W = 940 Kglm3 $ =Angle of Earth Frustrum =15° B3 = 0.65m 1+Sin15° F =1/2 x 940 x (hF x - - - - x 0.65 1-Sin15° h =..J (F/518.86) F1 = ST = 8283 Kgs h =..J (8283/518.86) = 3.996m Since h > (2,4-0.5)m therfore the soil pressure will only be mobilised in (2,4-0.5) Le .. 1.9m depth. Resisting soil force F = 518.86x1.9 2 = 1873.09 kg Moment due to side thrust at the base of the footing = 8283* (2.95+0.225) - 1873.09 x (0.55+ 1.9/3) = 24082.70 kg m
J
6,4
BROKEN WIRE CONDITION (LONGITUDINAL SIDE THRUST) Side thrust force = (F)
=1f2 x W x h2xB3 x
1+Sin
'1>
l-Sin $ Where W = 940 Kg ml ~ = Angle of Eath Frustrum 83 = 0.65m
=15°
"I
1+Sin15°
F = 112
X
940
X
(hF X - - - - - - x 0.65 1-Sin15°
h = v(F/518.86) Fl =SL = 4983 Kgs h = ~(4983/518.86) = 3.099m Since h > (2.4-0.5)m therfore the soil pressure will only be mobilised in 1.9m depth. Resisting soil force F = 518.86
X
1.92= 1873.09 kg
Moment due to side thrust at the base of the footing = 4983x(2.95+0.225) - 1873.09x(O.55+ 1.9/3) = 13605.2 kg m V 7.0
Check for Bearing Capacity
165598/1.036+ 11523
2x(165598/1.036)xO.192570xO.6
+ --------------
NC= 5.19 2
1/6x5.19]
16538.86 1818.85 + --------- + --------1/6 X 5.19] 1/6x5.19] = 6362' + 1585.3 710+ 78 = 8736 kg/m2 < 13675 kg/m2
Hence O.K.
154376/1.036 + 11523 BWC=
2 x (154376/1.036)xO.192570x(0.6) + -------------1/6x5.19J
5.19 2 24082.70
13605.2
+------ +-----1/6 x 5.19]
1/6x5.19]
= 9056 Kg/m2 < 13675 Kg/m2 B.O
· '!
Hence O.K
Design of Chimney A)
Compression with bending
Area of steel in compression ASC = 24x n/4 x(2.0)2 = 75.40 cm 2 . percentage of steel p/fck = 1.785/15 =0.119
, I.
= p = ASClB3 2 X 100 :B3=65 cm =1.785
59
Normal Condition Puc
=165598 Kgs =1624516 N
Puc
1624516 - - - - - - = 0.256
--= fck.bd
15x650x650
.x d' =50(20/2) =60 therefore d'/d =0.10
d =650
As per chart 44 of 5p.16 For the values of Puc/fckbd Mux1/fckbd 2 =0:65 -+ Mux1
= 0.256 & p/fck = 0.119
=0.165x15x650x650 2 = 679.7 X 10 N-mm 6
= 679.7 KN-m
Also Muy1 = 679.7 KN-m From the calculation shown in $ 6.0 Moment at the root of the chimney Mux =5907x(2,4+0.225) - 1873.09x(1.9/3) =14320.21 kg m =140.5 kN m Muy =825x(2.4+0.225) - 825x(1.261/3) =1818.88 kg m =17.84 kN m Ref: Clause 38.6 of 15-456-1978 PUZ
PUC
=0,45xfckxAC+0.75 fy ASC =0,45x15x(650)2+0.75x415 x{24x1t/4x20 =5198650.2 N =5198.65 KN =165598 Kgs =1624.5 KN
PUC
. 1624.5
--= PUZ
=0.3125 5198.65
for PUC/PUZ
f ::~::)
2)
=0.3125; ocn =1.1875
r
+
::~::) r ~
= 0.154+0.013 = 0.167 < 1.0 Hence O.K.
___ 17.84 11.1875
'r-_ _ _ ] 1.1875+ 140.50
+ 679.7
679.70
)..
BROKEN WIRE CONDITION
PUC =154376 kgs =1514.4 KN PUC/fckbd =1514.4x1000/15x650x650 =0.239 p/fck =0.119 .As per chart 44 of SP16 MUX1/fckbd 2 =0.167 MUXI =0.167x15x650x65Q2 = 687.90 x 10' N-mn =687.90 KN-m Also MUY1 =MUXl =687.90 KN-m From the calculation shown in $ 6.0 Moment at the root of the chimney Mux
= 8283x(2.4+0.225) - 1873.09x(1.9/3)
=20557.21 kg m =201.67 kN m =4983x(2.4+0.225) - 1873.09x(1.9/3) =11894.71 kg m
Muy
= 116.69 kN m
=" 5198.65 KN
PUZ
PUC/PUZ
(MUX)
=1514.4/5198.65 =0.2913; ocn =1.152
l"n
[ (MUX1)
J •
1.152
201.67 [ 687.90
=0.243+0.129 =0.373 < 1.0 Hence OK B)
Tension with Bending NORMAL CONDITION
PUt
=140917 Kgs
=1382396 N
PUtlfckbd =1382396/15x650x650 =(-)0.22 p =1.785 p/fck =0.119 d'/d =0.10 From Chart 79 of SP 16 61
J1.152 .
116.69 ] [ 687.90
Muxl/ fck bd2 =0.085 Muxl :; 350.15 kN m Muxl Muyl 350.15 kN m
=
=
Mux =140.5 kN m Muy = 17.85 kN m As per c1. 38.6 of 15-456-1978
[::~::) r
+
[
:~::)
r:
=1.0 for tension with bending
ocn
(MUX) ]
140.5 350.15
(MUY) ]
+
[ (MUX1)
=[
1.0
[ (MUY1)
I
+
[
17.85 350.15
I
=0.452 < 1.0 Hence O.K. BROKEN WIRE CONDITION
=130185 Kgs
PUt
=1277.1 kN PUt/fckbd
= 1277115/15x650x650 = (.)0.202
p = 1.785 p/fck =0.119 d'/d =0.10 From Chart 79 of 5P 16 Mux1/ fck bd 2 =0.09 Mux1 370.75 kN m Mux1 Muy1 = 370.75 kN m
=
Mux =201.67 kN m Muy =116.7 kN m As per c1. 38.6 of 15-456-1978 ocn (MUX)
+
[
ocn
(MUY)
< 1.0 [ (MUX1)
an
(MUY1)
=1.0 for tension with bending
[ (MUX) (MUX1) -
1
::~::) ]
+
[
+
[:::::: ]
1
-
[201.67] 370.75
= 0.858 < 1.0 Hence O.K.
9.0
Design of Base Slab Design Bearing Pressure = (PIA) + (P.ex/Z) +MAX{ST moment, SL moment}!Z = 6362 + 1585.3/2 + 710 = 7865 kglm2 ~ 0.07715 N/mm 2 d, = Eff. depth at Section XX = 550-50-16-8 = 476 mm d2= Eff. depth at Section YY = 350-50-16-8 =276 mm
a)
COMPRESSION REINFORCEMENT (i) Bending Moment at Section X-X
I
'
Bearing Pressure = 7865 kglm2 = 0.07715 N/mm 2 MUX1 = 0.07715x (8-83)2/8 x 5190 = 0.07715 x (5190-650)2/8 x 5190 1031708030 N-mm = 1031.6 kN m
=
MU, LIM = 0.36 Xu, Max/d (1-0.42 Xu, max/d) bd 2fck As per C1. 37.1 f of IS - 456 for Fe 415 grade steel Xumax/d = 0.48 Mu, LIM = 0.36x0.48 (1-0.42xO.48)x1740 x (476)2x15 815.8 kN m < 1031.7 kN m '-,-
=
Mux1/bd1
= 1031.7 x 10' I (1740x476 2) =2.618> 2.06
Hence section to be designed as doubly reinforced section. d'/d (50+16+8) 1476 0.15
=
=
63
From table 49 of SP 16 Pt 0.8956, Pc 0.192 Hence Ast (1740x476xO.8956)/l 00 7418 mml Provide 37 bars of 16mm dia. Ast provided =7437 mm1> 7418 mml Asc =(1740x476xO.192)/100 =1590.2 mml Provide 8 bars of ·16 mm dia. This is the minimum reinforcement to be provided at section
=
(ij)
= = =
x-x for uplift.
Bending Moment at Section Y_ Y
Muy1·
=0.07715 x(5190-1740)1 x 5190/8 =595.73 kN m
.
Muy1/bd1
= 595.73 x 10'1 (4690x2762) =1.67 < 2.06 Hence section to be designed as singly reinforced section. From table 1 of SP 16 Pt 0.546 Hence Ast (4690x276xO.546)/l 00 =7068 mm2Provide 37 bars of 16mm dia. Ast provided 7437 mm2> 7067 mm2
=
(bJ
= =
UPLIFT REINFORCEMENT
=1409171 (5.19 -0.65 =5314.9 Kglm2
Bearing Pressure P2
2
2)
=0.052139 N/mm 2
(j)
Bending Moment at Section X-X
MUX2
=0.052139 x (5190-650)2/8 x 1000
=134333520 N-mm/M
MUX2 = 0.87 x 415 x Ast x 476 (1 - Ast x 415/1 000~15) Ast 820.81 mm21M-width = 8.21 eM2 1M-width Ast reqd. =8.21x1.74 14.29 eM2 Provide 8 bars of 16 mm • Ast Provided 16.08 em2> 14.29 cm 2 Hence depth provided at Section X-X is ok.
C7
= -~
=
=
(ij)
Bending Moment at Section Y_ Y
= = =
=
MUY2 0.052139 x (5190-1740)2 I 8 x 1000 77573055 N-mm/M MUY2 =0.87 x 415 x Ast x 276 (1 - Ast x 415/1000x276x15) Ast 850.9 mm 2/M-width a.51 eM2 1M-width Ast reqd. =: 8.51x4.69 39.91 eM2 Provide 22 bars of 16 mm • Ast Provided 44.22 em 2> 39.91 eM2 Hence depth provided at Section Y-Y is ok.
=
=
;
,
c).
CHECK FOR ONE WAY SHEAR
At Section X-X Design bearing Pressure p 7 0.07715 N/mm 2
Shear force =VI =
B-B 1
xP
-d1
2
=0.07715x[(5190-650) /2-476] x1000 =138407 N/M width
=138407/476x1 000 =0.291 N/mm2
Shear Stress
% of Steel (p) =(Ast/bd)x1 00 = ((74.37x100) / (5190x476) xl00 = 0.301 As per table 13 of IS-456-1978 Allowable Shear Stress 0.3806 N/mm2>0.291 N/mm2 Hence O.K.
=
At Sec-Y-Y p = 0.07715 N/mml
=
Shear force:: V2
B-B 2 - d2
xp
2
':: 0.07715x [6190-1740) 12-276 )x1000 :: 111790 N in ShearStle$:: 111790J276x1000 :: 0.4050 NAn 2
=
Ast/bdxl00 74.37xl00/ (5190x276) xl00 = 0.5192 . Allowable Shear Stress = 0.468 N/mm 2>0.405N/mm 2 Hence OK d).
CHECK FOR 7WO WAY SHEAR
At Section X-X
=
p 0.07715 N/mm 2 Shearforce ='V2 [B2-(B J+D1)2] x p =0.07715x[51902-(650+476)2] 1980304 N Shear Stress 1980304/4x476[650+476] 0.924 N/mm2
=
= =
65
Allowable Shear stress = 0.25 x (15) 1/2 . = 0.968N/mm2 > 0.924 N/mm2 Hence OK
At Sec-y-y p = 0.07715 N/mm2 5hearforce = V2 [B2-(B 3+01)2] x p = 0.07715x[519()2(1740+276)2] = 1764563 N Shear Stress = 1764563/4x276[1740+276] = 0.793 N/mm2 Allowable Shear stress = 0.25 x ..J15 = 0.968N/mm2 > 0.793 Hence OK e)
CHECK AGAINST UPROOTING OF STUB:
Design Uplift = 140917 Kgs. Stub section = 200x200x16 Stub depth below GL = 2800 mm UltLoad resisted by stub in slab due to Bond Us = [Ox{Xx2.0+(X-Ts)x2.0}-Npx{X+(X-Ts)}xklxs Where X = flange width of stub. o = Depth of stub in slab. s = Ultimate permissible bond stress between stub & concrete Ts = Thickness of stub section. Np = No. of cleat pair (pair consist of outer and inner cleat) k = Flange width of cleat section. Us = [40x{20x2+(20-1.6)x2.0}-3x{20+(20-1.6)x11]x10 = 18048 Kg. Ultimate permissible bearing stress in concrete = 68.84 kg/cm2 Use outer cleat = 3 nos. 11 Ox11 Ox8 - 440 mrn long yse inner cleat = 3 nos. 11 Ox11 Ox8 - 250 mm long . provide 4 nos. of"16 dia. bolts per cleat pair of 5.6 grade
Load resisted by cleat in bearing Uc Where b Lo U Ct
= bx(Lo+U)xNpx(k-Ct) = Ultimate Bearing pressure in concrete = Length of Outer cleat = Length of Inner cleat = Thicness of cleat section. --':;-1
Uc=68.84~~9+25)x3x(11-0.8)
= 136923 Kg
(j)
:
{
Ultimate shear strength of bolts Ub
= total no. of boltsx2.0x2.01 x3160 (considering M-16 bolt gradeS.6 & double shear for cleat connected in pair) = (4x3)x2.0x2.01 x3160 = 152438 Kg (ii)
Ultimate bearing strength of bolt in stub or cleat = Total nos. of boltsx1.6x(Ts or2xCt)x5200 take Ts or2xCt which ever is less = (4x3)x1.6x1.6x5200 = 159744 Kg (iii) Effective strength of stub and cleat = Us+ .Least of the strength of case [ (i), (ii), (iii) ] = 18048+136923 = 154971 Kg which is more than UIt.Uplift=140917kg (Hence safe) f)
CHECK FOR BOND: Design bearing pressure = 0.07715 N/mm2 (5190-2650) Maxm. Shear force =
- 476 [
1
x5190xO.07715
= 718333 N As per Appendix - E of Is - 456 - 1978 Xu/d = 0.87 fy Ast/0.36 fck bd 0.87x415x7437
=-------0.36x15x5190x476 = 0.2013
J = 1-Xu/d xl/3
=1-0.2013/3 =0.933
Bond Stress =718333/0.933x476x37x 1t x16 = 0.87/N/mm2 < 1.6 N/mm 2 Hence OK.
10.0
Check for Sliding
/
F1 =1/2x1.5x6480xO.65 =3159 F2 =1/2x (23'9'5+3831) x 0.9XO.65 =1821 F3 = (0.2/2) (38J2+4151)x1.74 = 1389 F4 =(0.25/2) (45-50+4151) (4.69+5.19)/2 =5373 F5 = (0.1/2)(4550+4710) x 5.19 = 2403
=14145 67
.I
.
'<.
1 t. C.
.,
.:"" Q \.
1 '"
.~
6 D •
I IJ
yr j '
G.L.
o o
o
... Ln
o
650Sq.
~
N
o o
o ,.,., «::)
o
N
o
11'1 N
--b~--\
o ... t----""'\
... ~---1740----~1
4710 kg.- m
(All dimensions ire in mm)
... ,• . . - - - - - - 4690--------1 .....- - - - - - - 5 1 9 0 - - - - - - - - t
Sketch - 2 F.O.S. in NC =14145/5907 =2.40 > 1.0 F.O.S. in BWC =14145/8283 =1.71 > 1.0 Hence OK.
n.o
Check for Overturning Resultant Side Thrust
= {59072+825 2)1/2 =5964 kg (ii) Under BWC = (8283 2+4983 2)112 = 9666 kg (j) Under NC
Total Overturning Moment Under NC -
(j)
= (140917/1.036)x(5.19/2 -5.19/6) + 5964x(2.9S+0.225) - 5338x(5.19/2 -5.19/6) = 245016 kg m (ij) Under BWC = (130185/1.036)x(5.19/2 - 5.19/6) + 9666x(2.95+0.225) - 5338x(5.19/2) -5.19/6} = 238849 kg m Total Resisting Moment = 1/2 x(68.327xl440 + 44.311 x940) x (S/6 xS.19) ~ 302843 kg m
"
Factor of Safety Under NC =302843/245016 =1.236 > 1.0 Under BWC = 302843/238849 = 1.268> 1.0 Hence O.K. 12.0
Quantities Per Tower
: 42.06 m3 + 5.39 m3 (M15) (Ml0) Excavation Volume: 361.68 M3 Reinforcement : 4962 Kgs.
Concrete Volume
13.0
Reinforcement Detail
13.1
BAR BENDING SCHEDULE
Sketch
Length
Bar~
(mm)
(mm)
t
No. of Bars ~::(.
5090
n
,
\.~
t·.,
Unit wt. wt.llength wtlTower (kg/m)
(kgs)
(kgs)
.
5090
16
76
1'58
611'21
2444'84
2690
16
16
1'58
68'00
272:00
5352
16
44
1'58
372'07 1488'28
3350
20
20
2· 47
165'49
661'96
2307
6
13
0·22
6·60
26'39
Totol
4893'47
1640
100
L
425
100 4590
~
100
100
3000
~ 550
0
550
4894 kgs
69
13.2
REINFORCEMENT SKETCH
_~,-r-_~e.L.
Bar Mkd' 0 ' (4) bars of 20
650---'
o o
t
I
Bar Mkd 'E' (6mm _@ 250mm c/c)
N
'B,I
Bar Mkd (8+8) bars of 16
I
t
Bar Mkd 'e' (22+22) bars of 16 t
• 1740 4690
•
• •
·1
.,
5190
Sketch
Bar Mkd 'A' (38+38) bars of 16
\ kg metres In
'0 bewritt..
pressure design
•
3: Reinforcement
ILLUSTRATION - III PARTIALL YSUBMERGED TYPE FOUNDATION
e.l. G.l.
1 433
0 0
§ If)
o o 0 0
N
0
10 N
~ 0
10
~==============dAIi dimensions
l
\-
::0 "' _I
.Iore in mm J_.
~________~5~78~0~________
Sketch 4
"Partially Submerged Type Foundation"
I
1.0
\
Volume of Concrete (Cu.m)
5.78 2xO.05 5.78xO.l0 0.25/3 [5.782+5.28 2+5.78x5.28] 1.882X0.200 0.65 2 x (2.4 + 0.225)
'
= 1.670 = 3.341 = 7.651 = 0.707 = 1.109
.)
TOTAL )
= 14.478
.'
2.0
Overload Due to Concrete (Kg)
2
(0.65 x 0.225) 2400 (0.65 x 1.5) x (2400-1440) (14.478-0.095-0.634)x(1400-940) 0.65 2 x 0.75x(2400-1440) (14.478-1.670-0.09S-0.317)x(1400-9OO}
= = = = =
2
~,-\o
comp
Jplift
228 608 6325·
228
304 5702 7161
\
. 3.0
Dry 50;1 Volume: (Cu.m)
Al = 5.78 2+4x5.78xO.563 +1t x(0.563)2 = 47.413 A2 = 5.782+4x5.78x(0.563 + 0.433) + 1t x(0.563+0.433)2=59.544 V=0.75/3[47.413+S9.544+..[47.413x59.544] = 40.023 CU.M. \ \
4.0 .
Wet 50;1 Volume: (Cu.m)
5.782 X 2.2 5.78 X 0.563x2x2.1 n/3xO.563 2x2.1 TOTAL
)
!
::.
73.498 13.660 0.696
=
87.854
=
=
5.0
Check for Vplift:
5. 1
RESISTANCE AGAINST UPLIFT:
= 40.023 X 1440 + 87.854X940 + 6234 = 146450 Kgs.
F.O.S (NC) F.O.S (BWC)
= 146450/140917 = 1.040 > 1.0 = 146450/130185 = 1.125 > 1.0
71
6234
6.0
Check for Bearing Capacity
165598/1.036+7161
165598/1.036xO.192570xO.6x2
+
NC=
1/6x5.78J
5.78 2
16539
+
1820
+ 1/6x5.78J
1/6x5.78J
=6717 Kglm2 < 13675 kglm2 154376/1.036xO.192570xO.6x2
154376/1.036+7161
BWC =- - - - - - -
+ 1/6x5.78J
13605.2
24082.53
+
+ 1/6x5.78J
1/6x5.78J
= 6916 Kglm2 < 13675 kglm2
7.0
Design of Chimney
Calculations are similar to those given for Wet Type Foundation. B.O
Design of Base Slab
Basic design calculations are similar as given in Wet Type foundations. 9.0
Check for Overturning
Basic design philosophy is similar as given in wet foundation. 10.0
Check for Overturning
Basic design philosophy is similar as given in wet foundation. 11.0
Quantities Per Tower
Concrete Volume (MJ) Excavation Volume Reinforcement 12.0
51.23 (M15) + 6.68 (M1 0) 443.6 yn3 6050 Kgs.
Reinforcement -Details
Similar to those given in wet type foundations. 12.1
REINFORCEMENT SKETCH:
Similar to that given in wet type foundations. 12.2
BAR BENDING SCHEDULE
Similar to that given in wet type foundations.
ILLUSTRATION: IV FULLY SUBMERGED TYPE FOUNDATION
G.l.
0 0
'it
N
0 0 0
~
0 0
N
0 to
N
0 0 0
to
Sketch.5: "Fully Submerged Type Foundation." ALL DIMENSIO'NS ARE IN MM. 1.0
2.0
Volume of Concrete (Cu.m)
6.36 2 x 0.05 6.36 2xO.10 0.25/3[6.36 2+5.86 2+6.36x5.861 2.022X 0.2 0.65 2x2.625
=2.023 =4.045 =9.338 =0.816
TOTAL
=17.331
=1.109
Overload Due to Concrete (Kg.)
./ (0.65 2 x 0.225) x 2400 (0.65 2xO.75) x (2400-1440) (1 i.331-0.095-0.317)x(1400-940) (17.331-2.023-0.095)x0400-940)
= = =
COM 228 304 7783
=
UPLIFT 228
6998
8315
73
7226
•• •
3.0
Dry Soil Volume.: Nil
4.0
Wet Soil Volume: 6.362 x 2.95 6.36 x 0.764x2x2.85 1t/3xO.7642x2.85
= 119.33 = 27.684 1.740 =
TOTAL
= 148.750
I :1 I I
J
5.0
Check for Uplift
»
5.1
RESISTANCE AGAINST UPLIFT:
I
=148.750 x 940 + 7226 =147051 Kgs.
=
=
F.O.S (NC) 147051/140917 1.043> 1.0 F.O.S (BWC) = 147051/130185 = 1.130> 1.0 6.0
Check for Bearing Capacity
165598/1.036+8315 NC=
165598/1.036xO.192570xO.6x2 +
6.362
+
1/6x6.363
16538.8
1819.13 +
1/6x6.363
1/6x6.363
=5446 Kglm2 < 13675 kglm2 154376/1.036xO.192570xO.6x2
154376/1.036+8315 BWC=
+
6.362
13605.2
24082.53
+ - - - -l 1/6x6.36
1/6x6.36l
+
1/6x6.363
= 5571 Kglm2 < 13675 kglm2
7.0
Design of Chimney Calculations are similar to those given in Wet Type Foundation.
B.O
Design of Base Slab Basic design calculations are similar to those given in Wet Type Foundations.
9.0
Check for Sliding Basic design philosophy is similar to that given in wet type foundation.
10.0
Check for Overturning Basic design philosophy is similar to that given in wet type foundation.
U.O· Quantities Per Tower Concrete Volume (M3) Excavation Volume
61.23 (M15) + 8.09 (M10) 532.27' Yv'~
12.0
12.1 12.2
Reinforcement Details
Similar to those given in wet type foundation. REINFORCEMENT SKETCH Similar to that given in wet type foundation. BAR BENDING SCHEDULE Similar to that given in wet type foundation.
ILLUSTRATION: V WET BLACK COTTON SOIL TYPE FOUNDATION
G.L.
o o o rt)
o o
o
'fit N
10 Q)
N
o
N
Leon concrete ... .... 2180
.0 •..
'
6590
I~
.. I
709~
S ketch 6~'IIWet Black Cotton Soil Type Foundat ion II "ALL DIMENSIONS ARE IN MM" t·
1.0
Volume of Concrete (Cu.m) 7.09 2 x 0.05 7.09 2 xO.100 0.25/3 [7.09 2 + 6.59 2 + 7.09 x 6.59) 2.18 2 x 0.2 0.65 2 x 2.625
2.513 5.027 11.702 = 0.950 = 1.109
= 21.302
TOTAL 2.0
= =
=
Overload Due to Concrete (Kg.)
(0.65 2 x 0.225) x 2400 = (21.302-0.095) (2400 - 1440) = (21.302-2.513-0.095) x (1400··940) =
Comp
Uplift
228 20359
228 8599
-------------------20587 8827 75
3.0
Wet Soil Volume (Cu.m) 7.09 2 x 2.95 = 148.290 M3
4.0
Dry Soil Uplift Nil
5.0
Check for Uplift = 148.290 x 940 + 8827 = 148220 Kgs. F.O.S (NC) = 148220/140917 = 1.052 > 1.0 F.O.S (BWC) =. 148220/130185 = 1.140 > 1.0
6.0
Check for Bearing Capacity
165598/1.036+20587 NC=
7.092
+
+
17450.0 1/6x7.09J
165598/1.036xO.192570xO.6x2 1/6x7.09J 1551
+
1/6x7.09J
= 4530 kg/m2 < 13675 Kg/m2 154376/1.036xO.192570 xO.6x2
154376/1.036+20587 BWC=
7.09 2
+
24993.0 1/6x7.09J
+
+
1/6x7.09J 14516 1/6x7.09J
= 4620 Kg m2 < 13675 Kg/m2 7.0
Design of Chimney Calculations are similar to those given in Wet Type Foundation.
B.O
Design of Base Slab Basic design calculations are similar to those given in Wet Type Foundations.
9.0
Check for Overturning Basic design philosophy is similar to that given in Wet type foundation.
10.0
Check for Overturning Basic design philosophy is similar to that given in wet type foundation.
11.0
Quantities Per Tower Concrete Volume (M J ) Excavation Vol"ume Reinforcement
12.0
75.16 (M15) + 10.05 (M10) 655.36 \tV\3 8800 Kgs.
Reinforcement Details Similar to those given in wet type foundation.
12.1
REINFORCEMENT SKETCH: Similar to that given in wet type foundation.
12.2
BAR BENDING SCHEDULE: Similar to that given in wet type foundation.
ILLUSTRATION-VI DRY FISSURED ROCK TYPE FOUNDATION
1037
0 0
~
0 0 0
N
rC')
0 0 (\J
0
It)
(\J
0
Q
2
l
,-
I-
16 4190
' J
All ~imensions
-I
art! In
-I
4690 ~------------~~--------~~
Sketch"7: Dry Fissured Rock Type Foundation II
All DIMENSIONS ARE IN MM"
1.0
Volume of Concrete (Cu.m)
4.69 2 X 0.050 4.69 2x 0.100 0.25/3 [4.69 2+ 4.19 2+ 4.69 x 4.191 1.622 X 0.2 0.65 2 x 2.625 TOTAL
2.0
Overload Due
to Concrete (Kg.)
(0.65 2 x 0.225) x 2400 (9.868-0.095) (2400-1700) (9.868-0.095-1.100) x (2400-1700)
= = =
= 1.100/ 2.200 / = 4.934 = 0.525 .// --
;:;
1.109 .
=
9.868
~""'"? 228 6841
"'pt.,! \228 6071
- 7069 -77
6299
mm
3.0
Dry Soil Volume (Cu.m)
=64.890 = 27.731 = 3.211 = 95.832
4.691 x 2.95 4.69xl.037x2x2.85 1r/3xl.0371 x 2.85
TOTAL 4.0
Wet Soil Volume: Nil
5.0 5.1
Check for Uplift RESISTANCE AGAINST UPLIFT
=95.832 x 1700 + 6299 =16913 Kgs.
F.O.S (NC) =169213/140917 =1.200> 1.0 F.O.S (BWC) = 169213/130185 = 1.300> 1.0
6.0
Check for Bearing Capacity
165598/1.036 + 7069
165598/1.036 x 0.192570 x 0.6 x2
+
NC=
1/6x4.69 3 14676.0
+
=10701
1910
+ 1/6x4.691
1/6x4.691
K&,m2 < 62500 K&,m2 154376/1.036+7069
154376/1.036 xO.192570xO.6x2
BWC=-------------- + 1/6/6x 4.69 3 22220.0
+
.1/6x4.693
=11075 K&,m2 7.0
11743
+ 1/6x4.693
< 62500 K&,m2
Design of Chimney
.
Basic design calculations are similar to those given in Wet Type foundation. B.O.
Design of Base Slab
Basic design calculations are similar to those given in Wet Type Foundations. 9.0
Check for Sliding
Basic design philosophy is similar to that given in wet type foundation. J0.0
Check for Overturning
Basic design philosophy is similar to that given in wet type foundation.
11.0
Quantities Per Tower
35.07 (M15) + 4.40 (M1 0) 233.71 ml 4150 Kgs.
Concrete Volume (Ml) Excavation Volume (NEAT) Reinforcement 12.0
12.1 12.2
Reinforcement Details Similar to those given in wet type foundation. REINFORCEMENT SKETCH:
Similar to that given in wet type foundation. BAR BENDING SCHEDULE Similar to that given in wet type foundation.
ILLUSTRATION-VII SUBMERGED FISSURED ROCK TYPE FOUNDATION
8v C\J
o o o
o
oN
r()
~
N
o o o 10
Lean concrete (I : 3: 6) • • • • • Do.
•
6>
•• ,
2080
..
••••
• •••
All dimensions are in mm.
6090 6590 "
Sketch-8: Submerged Fissured Rock Type Foundation" "ALL DIMENSIONS ARE IN MM" 1.0
Volume
of Concrete (Cu.m)
2
6.59 x 0.05 6.59 2 x 0.10 0.25/3 [6.59 2 + 6.09 2 + 6.59 x 6.09) 2.08 2 x 0.2 0.66 2 x 2.625 TOTAL
= 2.171
= 4.343 =10.054
= 0.865 = 1.143 =18.577 79
2.0
Overlo~d Que
tp CqlJcrete (Kg.) COMP 235 8501
2
(0.66 x 0.225) x 2400 = (1 a,577 -.098) x (1400-940) (18.577 -0.098-2.171) x (140~940)
= =
UPLIFT 235
7502 8736
3.0
Dry $q;1 volu~ : Nil
4.0
Wet Soil volume: (Cu.m)
=
=
128.113 18.877 0.754
=
147.744
6.59 2 x 2.95 2 x 6.59 x 0.503 x 2.85 1t /3x (0.503) 2x2.85 = TOTAL
5.0
Check for Uplift
5.1
RESISTANCE AGAINST UPLIFT:
7737
=147.744 x 940 + 7737 =146616 Kgs.
F.O.S (NC) =146616/140917 =1.040> 1.0 F.O.S (BWC) = 146616/130185 =1.130> 1.0
6.0
Check for Bearing Capacity
NC
=
165598/1.036 x 0.192570xO.6x2
165598/1.036+8736
+ 1/6x6.59 3 16902.0
1787
+-----
+ 1/6x6.59 J
1/6x6.59J
154376/1.036+8736
154376/1.036xO.192570xO.6x2
+
BWC= 6.59 2
1/6x6.59 J
24445.0
13968
+
+ 1/6x6:59
J
= 5160 Kg/m2 < 62500 Kglm2
1/6x6.593
7.0
Design of Chimney Basic design calculations are similar to those given in wet type foundation.
B.O
Design of Base Slab Basic calculations are similar given to those in Wet Type Foundation.
9.0
Check for Sliding Basic design philosophy is similar to that given In wet type foundation.
10.0
Check for Overturning Basic design philosophy is similar to that given in wet type foundation.
11.0
Quantities Per Tower Concrete Volume Excavation Volume Reinforcement
65.62 (M15) + 8.69 (MlO) Ml 478.25\,,\~
7750 Kgs.
12.0
Reinforcement Details Similar to those given in wet type foundation.
12. 1
REINFORCEMENT SKETCH: Similar to that given in wet type foundation.
12.2
BAR BENDING SCHEDULE: Similar to that given in wet type foundation.
ILLUSTRATION: VIII DRY TYPE FOUNDATION
10
r-..
-
0
0 0
en
(\J
10
en
(\J
10
~
o
10
~_---.JL..-.-
All dimensions __
L _ _ _ _ _ _ _ _ _ _ _ _ _ _----!. ore in mm
~
4070
.\
Sketch 9: Dry Type (PCC) Foundation /I
ALL DIMENSIONS ARE IN MM" 81
1.0
. Volume of Concrete (Cu.m)
4.07 2X 0.05 1.725/3 .[4.072+ 0.622 + 4.07 x 0.62] 0.622 x (1.175 + 0.225)
0.828 =11.197 = 0.538
=12.563
TOTAL
l.O
~
Overload Due to Concrete (Kg.)
COMP/UPlIFT
=
0.622 x 0.225 x 2300 02.563-0.0865) (2300-1440)
199
= 10730 10929 -
3.0
(. I
I
'Jl
Dry Soil Volume (Cu.m)
4.07 2x 2.95 4.07X1.674X2X2.9
I -) .
= 48.867 = 39.516 = 8.510
1tI3x(1.674)2x2.9
TOTAL
\ '3. . .~
Wet Soil volume: Nil
S.O 5.1
Check for Uplift RESISTANCE AGAINST UPLIFT:
'< .--
"
Ij
-
--
."
= 96.893
4.0
~
, ,
..
..::
t
=96.893·x 1440 + 10929 =150455 Kgs. F.O.S. (NC) F.O.S (BWC) 6.0
=150455/140917
=150455/130185
=1.068> 1.0
=1.156> 1.0
Check for Bearing Capacity
NC
=
165598/1.036+ 10929
. 2x165598/1.036xO.192570 x1.775
+ 4.07 2
1/6x4.071
17475.0
+----
1340
+
1/6x4.07J
= 21708 Kglm2 < 27350 Kglm2
1/6x4.07J
154376/1.036+10929 BWC=---------------
2x154376/1.036XO.192570x1.775 +
1/6x4.073
25020.0
14541
+------
+ 1/6 X4.07 3
1/6 X4.07 3
= 22272 Kwm2 < 27350 Kglm2
7.0
Design of Chimney
Basic design calculations are similar to that given in wet type foundation. B.O
Check for Sliding
Basic design philosophy is similar to that given in wet type foundation. 9.0
Check for Overturning
Basic design philosophy is similar to that given in wet type foundation. 10.0
Quantities Per Tower
Concrete Volume Excavation Volume Reinforcement
: 50.252 m3 : 225.34 m3
ILLUSTRATION·IX HARD ROCK TYPE FOUNDATION 1.0
Volume of Concrete
0.65 2 x 0.225 1.65 2x 1.250
= 0.095
TOTAL
= 3.498
= 3.403
,; "
2.0
Overload of Concrete
0.095 x 2300 3.403 x 860
= 219 = 2927
6:'1>00-\44 D)
TOTAL
= 3145
83
.
c.L. III
~
G.L.
650 Sq, ......
Rock level
o
III N
....
o
o ....
o
III
.... N
o
o
III III N N +1
....
•
-~
I-~
0 III
• ¢= dia
22.54>-i
-4'
o
•
• of grout bar
•
e
-t-
III +1
o o
....'"
0 III
12 bars of
-4'
20'mm'7
• 0 III
-4'
III N
....
•
III N +1
125 ±2S
•
•
1.50
1.50
• 450
1600!50 U __ ..I
0 __ 1.
~_
.. _...a_,,: __
125 ±25 ~
3.0
Bea,ing CaP.1City 165598 + 3145
NC
= - - - - - - - = 70237 Kglm2 < 1,25,000 Kglm2 1.552
BWC
4.0
154376 + 3145 - - - - - - - = 65565 Kglm2 < 1,25,000 Kglm2 1.552
=
theelc for Uplift DESIGN UPLIFT NET UPLIFT
= 140917 Kgs. = 140917-1.55xl.55x1.25x2300 =134010 Kgs.
UPLIFT RESISTED BY 12 NOS. 20, ANCHOR BARS: 12 X 1t X 2.0 x 115 x 16 = 138733 > 134010
5.0
-
Check Against Uprooting of Stub DESIGN UPLIFT = 140917 KG NO. CLEATS PROVIDED = 3 NOS. 11 Ox11 Ox8 (Outer & Inner) NOS. OF BOLTS = 12 NOS. O~ 16MM DIA. Ult. resistence of stub in Bond = Us =[115x (20x2+{20-1.6) x2.0) -3x {20 ... (20-1.6)} xl1]x 10 = 75648 Kg. LEAST RESISTENCE OFFERED BY CLEATS IN BEARING/BOLT: = 136923 Kg. . (REFER CHECK FOR UPROOTING OF STUB CAL.) RESISTENCE AGAINST UPLIFT: =75648+136923 = 21i571 > 140917
6. 0
Bond Between Rock and Concrete = 160 x 120 x 4x4
=307200 > 134190
NOTE 1: 1. 2. ·3. 4. 5.
Minimum depth of slab should not be less than 1000 mm. ., . Stub to be cut, Holes to be drilled .and cold-zinc rich paint/galvanising to be appliro at site. Grout holest to be 20 mm bigger than dia of grout bar. Cement sand mix 1:1 Ratio to be used for grouting through grouting pump. Entire concrete block (slab) should be embedded in hard rock irrespective of level of hard rock encountered.
85
ILLUSTRATION -X DRY SANDY SOIL (WITH CLAY CONTENT 5-10%)
C.L. G.L.
225
100 ~
I
~ I-
n....-.....J
•
r--240V"'~-~.
50
ITsin_
4150.I
4650
wI-- 1"""In ,
All dimensions ore In mm
Sketch X : Dry Sandy Soil (with Cloy Content 5-10%)
nALL DIMENSIONS IN SKETCH ARE IN MM'I
1.0
Volume of Concrete (Cu.m)
4.65 2 x 0.05 4.65 2 x 0.100 0.25/3 x (4.65 2 + 4.15 2 + 4.65 x 4 .15) 2.9 2 x 0.2 0.65 2 x 2.625
= 1.081 = 2.162 =4.845 = 1.682 = 1.109 10.879
2.0
Overload of Concrete (Kg.)
•
0.65 2 x 0.225 x 2400 0.65 2 x 2.4 x (2400-1440) 2.92 x 0.2 x (2400-1440) 4.845 x (2400-1440) 4.65 2 x 0.1 x 2400
3.0
= = = = =
Dry Soil Volume (Cu.m) 4.65 2 x 2.85 2 x 4.65 X 2.85 2 x TAN20 PI/3 x TAN2 20 X 2.85 1
= 61.62
=27.494 = 3.211 92.325
COMP 228 973 1615 4651 5189
UPLIFT 228 973 1615 4651 5189
12656
12656
.'
.,
4.0
Total Resistance Against Uplift
= 92.325 x 1440 + 12656 = 1.45604 KG F.O.S (NC) = 145604/140917 = 1.033 > 1:0 F.O.S (BWC) = 145604/130185 = 1.118 < 1.0 5.0
Check for Bearing Capacity
165598/1.036 + 1.036 + 12656
2x (165598/1.036) xO.192570 x 0.6
NC=
+
4.65 2
1/6 X 4.65 3
14676
1910
+
+ 1/6 X 4.65 3
1/6x 4.65 3
=11172 KG/M2 < 25000 kg/m2 154376/1.036 + 12656 BWC=
+
4.65 2
1/6x 4.65 3
22220
+
2x (154376/1.036f x 0.192570 xO.6
11743
+ 1/6 X 4.65 3
1/6x4.653
= 11558 KG/M2 < 25000 KG/M2 7.0
Design of Chimney
Basic design calculations are similar to those given in wet type foundation B.O
Design
of Base Slab
Basic design calculations are similar to those given in wet type foundation 9.0
Check for Sliding
Basic design philosophy are similar to that given in wet type foundation 10.0
Check for Overturning
Basic design philosophy is similar to that given in wet type foundation 11.0
Quantities Per Tower
Concrete Volume (CU.M) Excavation Volume (CUM.M) Reinforcement (KG) 12.0
: 39.192 (M15) + 4.324 (M1 0) : 294.03 : 2740
Reinforcement Details
Similar to those given in wet type foundation. 13.0
Reinforcement Details
Similar to those given in wet type foundation. 14.0
Bar Bending Schedule
Similar to that given in wet type foundation.
87
• • I
ILLUSTRATION -XI PARTIALL Y BLACK COTTON SOIL TYPE FOUNDATION
I
0 0
10
0 0
~
N.
0 0 0
0 0
N
0 0
-
10
I I I I ",
0
10 N
0
52
I1----\4
,-
2 00 4000
..,
.
-t
4500
0
JAilIn mmd,m.'::,o.. "•
C
I I I
•I I
Sketch XI: Partially Black Cotton Soil Type Foundation
I I
IIALL DIMENSIONS IN SKETCH ARE IN MMII
I
1.0
J
Volume of Concrete (Cu.m)
4.502 x 0.05 4.502 x 0.100 0.25/3 (4.50 2 + 4.002 + 4.50 x 4.00) 2.8 2 x 0.2 0.65 2 x (2.4-1.5) 0.65 2 x 1.5 0.65 2 x 0.225
I
=1.013
~
= 2.025
=4.521
= 1.568
=0.380 = 0.634
=0.095
10.240 2.0
Overload of Concrete (Kg.)
0.095x2400 0.0.634 x (2400-1440) 0.38 x (2400-1440) 1.568x (2400-1440) 4.521 x (2400-1440) 2.025 x 2400
= = = = =
=
COMP 228 609 365 1505 4340 4860 11907
UPLIFT 228 609 365 1505 4340 4860 11907
,
-
Al A2 V
3.1
-
= 4.5 2+ 4x4.5xl.35 X TAN30 + 1f"(1.35x TAN30)2 . = 36.188 = 4.5 2+ 4 X 4.5 (1.35 TAN 30 + 1.5 TANO) +1f(1.35 X TAN 30 +1.5 TANO)2 = 36.188 = 1.5/3 06.188+36.188 + (36.188x 36.188)1/2 = 54.2822
Volume o( Normal Soil (Cu.m)
4.5 2 X 1.35 2 X 4.5 X 1.35 2 x TAN 30 1f/3 (1.35 1 x TAN2 30)
= 27.338 = 9.470 = 0.8588 = 37.6668
4.0
Total Resistance Against Uplift
= 54.2822 x 1440 + 37.6668 x 1440 + 11907 = 144313 KG F.O.S. (NC) = 144313/140917 = 1.024> 1.0 F.O.S (BWC) = 144313/130185 = 1.108> 1.0
5.0
Check (or Bearing Capacity
2x (165598/1.036) x 0.192570 x 0.6
165598/1.036+ 11907 NC=------------------ + 4.50 2 17450
+ ---------
1/6 X 4.503
1551
+
1/6 X 4.50 1
1/6x4.501
=12165 KG/M2 < 25000 KG/M2 154376/1.036+ 11907 Bwe=
2X(154376/1.036)XO.192570XO.6 +
4.502
1/6X4.503
24993
+ 116 X 4.503 =
7.0
14516
+ 1/6 X 4.503
12815 KG/M2 < 25000 KGfM 2
Design o( Chimney
Basic design calculations are similar to those given in wet type foundation B.O
Design o( Base Slab
Basic design calculations are similar to those given in wet typ~ ioundation 89
9.0
Check for Sliding
Basic design philosophy is similar to that given in wet type foundation 10.0
Check for Overturning
Basic design philosophy is similar to that given" in wet type foundation 11.0
12.0
Quantities Per Tower Concrete Volume (CU.M.) Excavation Volume (CU.M) Reinforcement (KG)
36.908 (M1S) + 4.052 (MlO) 243.03 2600
'Reinforcement Details
Similar to those given in wet type foundation. 13.0
Reinforcement Sketch Similar to that given in wet type foundation.
14.0
Bar Bending Schedule
Similar to that given in wet type foundation.
";':
Transmission Line· Manual '. ;:
Chapter 11
Construction of Transmission Lines
I I I
CONTENTS Scope 11.1 Survey 11.2 Manpower, Tools and Plants and Transport Facilitie~ 11.3 Environmental Consideration 11.4 Statutory Regulation for Crossing of Roads, Power Lines, Telecommunication Lines, Railway Tracks, etc. 11.5 Survey IN '"=I M E7HcJi}S 11.6 Foundations 11.7 Erection of Super Structure and Fixing of Tower Accessories 11.8 Earthing 11.9 Stringing of Conductors 11.10 Hot-Line Stringing of E.H.V. Lines 11.11 Protection of Tower Footings 11.12 Testing and COmmissioning 11.13 References Annexures
Page 1
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t
3
I
4 4 10
16 17 19 24 26 26 26 27-54
j
• •
, -
,J ~ J J
CHAPTER-XI
CONSTRUCTION OF TRANSMISSION LINES A. SCOPE
9.
This chapter will cover the environmental consideration, Survey, Excavation, Stub-setting and Concreting, Erection of Towers, Stringing of Conductor for the Construction of: Transmission Lines.
11.1 SURVEY (i) Reconnaissance Survey (ii) Alignment Survey (iii) Detailed Survey It would also cover soil investigation of representative sites along the route of the line to establish the distribution of foundations in different types of soils. 11.1.1 Erection of Transmission Line Erection of transmition line cov~rs Check Survey, Excavation, Setting of Stubs, Casting of Foundations. Erection of Towers, Stringing of Conductors and Groundwire, Final Checking and Commissioning. 11.2 MANPOWER, TOOLS AND PLANTS AND TRANSPORT of ACILITIES 11.2.1 Survey Average output per month per gang consisting of about 10 persons will be: (i) Alignment Survey I5km or (ii) Detailed Survey 20km or 20km (iii) Check Survey Wherever topographical survey is to be carried out the output will be less and will depend on the quantum of work.
11.2.1.1 Tools required/or Survey Gang 1. Theodolite with stand 2. Dumpy level with stand 3. Ranging rod
,
INa 1 No 5 Nos 2 Nos
4.
Levelling staff
5.
Engineers chain 30m
INo
20m
1 No
30m
INa
15 m
1 No
6.
Steel Tape
7.
Survey umbrella
8.
Chain pins
1 No 30 Nos
10.
11.2.1.2
Spades, Knives and axes for clearing the bushes and trees Tents, buckets, water drums, camping cots, tables, chairs, and petromax etc
Asper requirement As per requirement
Transport required/or Survey Gang Jeep with trailor
INo
11.2.2 Excavation Stub-setting and Concreting Average output per gang consisting of about 85 persons per month will be Excavation 400-500 m3 Normal soil 60 m3 Soft rock + 180 m3 Normal soil 150 m3 Soft rock °
Output of Hand rock will depend on situation Stub-setting & Concreting
60-70 m3
11.22.1 Tools and Plants required/or Excavation, Stubsetting and Concreting Gang L Stub-setting Templates As. per requirement 2. Stub-setting Jacks -do3. Form boxes/Chimneys -do4. Mixer machine - Diesel engine driven I No - Hand driven 2 Nos 5. Needle vibrator INa 6. Dewatering pump 2 Nos 7. Air compressor for drilling holes in rock INa Asper 8. High carbon drilling rods for drilling holes in rock requirement 9.•Exploder I No INa 10. Water tanker trailor 11. Theodolite with stand INa 12. Ranging rod 3 Nos 13. Dumpy level with stand. INa 14. Levelling staff INa 15. Survey umbrella INa 6 Nos 16. Concrete cube mould Asper 17. Wooden shuttering & poles requirement
2
. _... _._-_._---------
2 Nos dia and of length - 8.5-9 m 700m Polypropylene rope -25 mmdia 1000m -19mmdia 8 Nos Single sheave pulley - closed type 4 Nos - Open type 16Nos Crow bars (25 mm dia and 1.8 m length) Spanners (both ring and flat) hammers, Asper slings (16 mm dia and 1 m length) requirement hooks, (12 mm dia) 'D: shackle, tommy-bars
18. Mixing sheets 19. MeasUring box 20. Metal screen - 40 mm mesh -20mm mesh - 12.5 mm mesh . 2l. Sand Screen - 4.75 mm mesh 22.. Empty barrel (200 litres capacity) 23. SteeVAlwninium/Wooden ladder (3.5 m length) 24. 30 m metallic tape 25. 30 m steel tape 26. Engineers' spirit level I 27. Steel piano wire/thread
12 Nos 6 Nos 1 No 1 No 1 No 1 No 6 Nos
28. 29. 30. 31.
Crow bar Pikaxe Spade Shovel
20 Nos 12 Nos 25 Nos 8 Nos
112.3.2
32. 33. 34. 35. 36.
Gamelas Buckets Iron r~mer (4.5 kg) Masonry trowel Manila rope - (38 mm dia) -(12 mm dia)
30 Nos 12 Nos
11.2.4 Stringing of Conductor Average output per gang consisting of about 200 persons per month will be Tension Stringing method - Machine stringing -15km (i) for 400 kV Single Circuit -8km (ii) for 400 kV Double Circuit
37. Pocking rod (16 mm dia) - 3 m length
5 Nos 1 No 1 No
5 Nos 6 Nos 150 m 30 m 2 Nos
/
2. 3.
4. 5.
6.
Tents, buckets, water drums, camping cots, tables, chairs and petromax etc.
50 m
39. Hammer, Tommy bar, plumb bob, (0.45 kg) . Hook, (12 mm dia) spanners (bQth ring As per and flat) etc. requirement 40. Tents, buckets, water drums, camping As per cots, tables and chairs, petromax etc. requirement
1.
. 3.
2 Nos
- 1.5 m length 2 Nos 38. Blasting materials, binding wire Asper requirement
1122.2
2.
Transport required/or Stub-setting & Concreting Gang Truck 1 No .(For transportation of metal and sand from source, cement, reinforcement steel and other materials from site stores) Tractor with trailor 1 No Motor Cycle 1 No
11.2.3 Erection or Tower by Built up Method Average output per gang consisting of about 50 persons per month will be - 80 mt
1.
2. 3.
As per requirement
Transport required/or Tower Erection Gang Truck 1/2 No 1No Tractor with Tailor 1 No Motor Cycle
-Skm for ± 500 kV HVDC Multi-Circuit Requirement of manpower and average output per gang for carrying out various types of transmission lines by manual method is furnished hereunder (iii)
Manpower Average Output (Nos) per month (kIn)
Sl No
Description of line
l. 2.
-P6 kV Single CiItuit
75
·6i6 kV Double Circuit
3. 4.
132 kV Single Circuit 132 kV Double Circuit
75 100 100
5. 6.
220 kV Single CiItuit
125
220 kV Double Circuit
125
30 .15
7.
400 kV Single Circuit
225
IS
8.
400 kV Double Circuit
225
8
30 15 30 15
112.4.1 Tools and Plants required/or Stringing Gang/or Tension/Manual Stringing l. TSE sets (Tensionar & Puller of 8/10t capacity) 1 Set" 2. Running block for conductor lOONos ~- Runninl!: block for earthwire 60 Nos
5. Pilot wire each of 800 m length 10 Nos 6. Pilot wire joint 12 Nos 7. Ground roller for Tension/Manual Stringing 30/1 00 Nos 8. Wire mesh pulling grip (one end open) of required dia for conductor 6 Nos 9. Wire mesh pulling grip (one end open) of required dia for earthwire 2 Nos. 10. Wire mesh pulling grip (double end open) of required size for conductor 4 Nos 11. Articulated joint - Heavy duty (20 t) 10 Nos - Medium duty (10 t) 10 Nos - Light duty (5 t) 5 Nos 12. Drum mounting jack for conductor drum of lOt capacity 4 Sets 13. Tum table (5 t capacity) 2 Nos 14. Anchor plate (1.5 m x 1.0 x 8 mm) with 15 Nos. Anchor pins (45 mm dia and 850 mm long) 10 Sets 15. Hydraulic compressor machine - 100 t capacity with die sets 8 Nos 16. Travelling ground 12 Sets 17. Dynamometer -10 t 4 Nos - 2t 2 Nos 18. Pilot wire reel stand 4 Nos 19. Four sheave pulley with 12 mm dia 300 m length wire .rope 6 Sets 20. Four sheave pulley with 9 mm dia and 300 m length wire'rope 2 Sets 21. Four sheave pulley with 12 mm dia and 150 m length wire rope 4 Sets 22. Equiliser pulley (lOt capaci ty) 16 Nos 4 Sets 23. Conductor lifting tackle 4 Nos 24. Winch - motorisedlmanual - 10 t Capacity 25. Comealong clamp for conductor (bolted type/automatic) 50/20 Nos 26. Comealong clamp for earthwire (bolted type/automatic) 15/10 Nos 27. Tirfor (5 t capacity) 6 Nos 28. Aerial (chair for conductor) 6 Nos 4 Nos 29. Aerial trolly 16 Nos 30. Tum buckle - lOt 6 Nos - 3t ... 31. Tension/Sag plate (for tensioning purpose) 6 Nos 8 Nos 32. Sag board 4 Nos 33. Marking roller 2 Nos 34. Mismatch roller 6 Nos 35. Joint protector
s s s J'"
:t
36. Walkie talkie set 4 Nos 37. Theodolite with stand 1 No 38. Thermometer 3 Nos 39. Survey umbrella I Nos 40. Hydraulic wire cutter 2 Nos 41. Binocular 3 Nos 42. Flag (red & green) 30 Nos 43. Crow bar (1.8 m length) 10 Nos 44. Nail pullar 6 Nos 45. Wire rope -(19 mm dia) 1000 m -(16 mm dia) 150 m -(14 mm dia) 900m 46. Polypropylene rope - (25 mm dia) 500 m - (19 mm dia) 500 m 47. 'D' - Shackle - 190 mm long 40 Nos -150 mm long 125 Nos - 100 mm long 125 Nos 48. Bulldog clamp - 100 mm long 35 Nos 49. Hammers, spanners, (both flat and ring) round files, flat files screw drivers, cutting pliers, steel and metallic tapes, hacksaw frame and blades, deadmenlS, scafolding, slings etc. Asper requirement 50. Tents, buckets, water drums, ~ping cots, As per table, chair, petromax etc. requirement
112.42 Transport required/or Stringing Tension stringing
Manual stringing
1. Truck
4 Nos
4 Nos
2. 75 h.p. Tractor
2 Nos
1 No
3. 35 h.p./45 h.p. Tractor 5 Nos
6 Nos
and trailors 4. Jeep
2 Nos
2 Nos
5. Motor Cycle
1 No
INo
11.3
ENVIRONMENTAL CONSIDERAnON The route of transmission line should be aligned in such a way as JO minimise damages to crops and cutting of trees. Special care should be taken to avoid routing of transmission line through lands particularly in Reserved/Protected forests. Even ifline length increases, efforts should be made to keep the line of forests. If forest land cannot be avoided, standard extensions should be provided minimise cutting of trees by ensuring adequate ground clearances. The line also should be kept away from villages, bulk storage oil tanks, oil .. pipe lines, airports, petrol pumps, cluster of hutments, buildings containing inflammable materials such as explosives, cotton godowns, factories, aerodromes Helipads etc.
•
4
11.3.1. I~portant requirement for Choice of Route The transmission line connects two points which may be two power stations, power station and another sub-station or two sub-stations. The line route has to be shortest connecting the two points. However, it is important that due weightage be given while selecting the route to the accessibility of the line for construction as well as for maintenance or its total life span. By sljght deviation increasing the route length marginally, the line should be sited in areas which are not inaccessible. It should be possible to transport the materials and tools quickly in case of breakdowns. Wherever roads are existing the line should be approachable from such roads. It should avoid as far as possible waterlogged areas or areas prone to flooding for long periods. The transmission line route should avoid inhabited areas leaving sufficient margi~for growth of villages. It should avoid as far as possible the areas where intensive cultivation is done. As far as possible crossing of orchards and gardens should be avoided. The additional costs to be incurred in crop compensation during construction and delay in attending to break downs during operation and maintenance should be carefully weighed against increase in the route length as also increase in angle towers. It should be possible for the men patrolling the line to be able to reach every location, careful inspection of the towers, insulators and the accessories without any obstruction from the land owners. With intensive irrigation in certain areas it may be cheaper to have slight deviation, rather than having litigation delaying the project apart from the cost to be incurred in making payment for compensation. Heavily wooded areas should be avoided. Prior consultations should be held with the concerned Departments. With these general remarks the various considerations for the choice of route and the construction of the line are discussed in detail in the following paras. 11.4 STATUTORY REGULATION FOR CROSSING OF ROADS, POWER LINES, TELECOMMUNICATION LINES,RAILWAY TRACKS ETC 11.4.1 Road Crossing On all major road crossings, including National Highways, the towers shall be fitted with double suspension or tension insulator strings depending on the type of towers used. 11.4.2 Power Line Crossing Where a line is to cross over another line of the same voltage or lower voltage, suspension/tension towers with stan{lard extensions shall be used. Wherever the line to be constructed is crossing another important line for which shutdown is difficult, susPension towers with required extensions in combination with dead end towers shall be used. 11.4.3 Telecommunication Line Crossing The angie of crossing shallbe~ as near 90 degrees as
angle of crossing is below 60 degrees, the matter shall be referred to the authority incharge of the telecommunication system. Also in the crossing span, power line support shall be as ncar the telecommunication line as possible to obtain increased vertical clearance between the wires. The crossiug shall be in accordance with the code of practice for crossing between power and telecommunication lines. 11.4.4 Railway Crossing For Railway Crossing, to~ers shall be Angle/dead,end type and railway crossing construction shall conform to the regulations for Electrical Line Crossings with Railway Tracks ,issued by the Ministry of Rail ways from time to time. 11.4.5 River Crossing In case of major river crossing, towers shall be of suspension type using double suspension strings and the anchor towers on either side of the main river crossing shall be dead end type. Clearance required by the navigation Authority shall be provided in case of navigable rivers. For non-navigable rivers, clearance shall be reckoned with respect to highest flood level (HFL). 11.4.6 Other Provisions 11.4.6.1 The transmission linein the vicinity of Aerodrome shall meet the requirement laid down by the Director General, Civil Aviation, Government of India. 11.4.6.2 Requisite vertical and horizontal clearance to adjacent structures shall be maintained as per I.E. Rules. 11.4.6.3 The electrical clearance required for different kinds of crossing are given in Annexure-' A'. SURVEY \ N C) M GTHa..6SThe survey of high voltage transmission lines must be carried out accurately and expeditiously. A mistake in the field or subsequent office work may cause unnecessary expendit~e and inconvenience. It is, therefore, essential that every care should be taken in seuing out; levelling and plotting the profile of the route. The care and fore-thought given at the first stage of surveying goes a long way in achieving economy and successful successive operational stages. The survey of the transmission line till now is being carried out in India by conventional methods using only the Topa sheets and instruments like vernier theodolite, dumpy level, engineers' chains or measuring tapes, for selecting the route and further field works. However, in advanced
11.5
t t
C1
'"'.... ,nr\' nf ,,"rvP\1;nIJ ~\l ~nnlip1i
tn trnm:mi~~inn
-• J J J
, I J
,
,I
1. 2.
Reconnaisance and route al ignment survey Detailed survey
3.
Tower spotting
4.
Check survey
115.1.1 Reconnaissance and Route Alignment Survey A provisional route of transmission line is initially plotted on survey maps and a reconnaissance walkover survey is carried ouL This is essential to fix up angle tower positions tentatively since many of the physical features on the ground may not be clearly available in the survey map due to developments that might have taken place subsequent to the preparation of the maps. The reconnaissance survey is essential to carry out to collect the first hand account of various important field data required for transmission line works. The general consideration to be kept in view while establishing the preliminary route at the time of reconnaisance survey are as under: 1. The route should be as short and as straight as possible. 2. It is advantageous to lay the line ncar to or along roadway. The line should be approachable as far as possible. 3. The number of angle towers should be minimum and within these, the nllmber of heavier angle towers shall be as small as possible. 4. Cust of securing and clearing ~ight of way (ROW), making access roads and time required for these works should be minimum. 5. Corridor through which line is taken should have sufficient space to take care of future load developments. 6. Crossing with permanent objects, such as railway lines and roads should be minimum and preferably at right angles (reference shall be made to the appropriate Railway regulations and Railway electrification rules as well as Civil Authorities for protection to be provided for railway and road crossings respectively. Guarding may not be necessary if fast acting protective devices are provided). 7. In case of hilly terrain having sharp rises ~d faIls in the ground profiles, it is necessary to conduct detailed survey and locate the tower positions. The proposition should be most economical and safe. The following areas should be avoided as far as possible while selecting route: 1. Marshy areas, low lying lands, river beds, earth slip zones etc. involving risk to stability of foundation. 2. Areas subject to floods, gushing nalas dwing rainy seasons,tanks, ponds, lakes, snow blizzards, hurricanes or similar extreme climatic conditions and nat~ral haz- . ards.
, 3. Areas which involve risk to human life, damage to public and private properties, religio·us places; civil and defence installations, industries, aerodromes and their approach and take off funnels habitation of important crops, good farming areas, uneven terrain, quarry sites or underground mines, gardens and plantations. 4.
Inaccessible areas where approach roads are not possible.
5. Areas which will create problems of right of way and way leaves. 6. Route involving abrupt changes in levels, too many long spans, river or power line crossings or near parallelism to telecommunication lines. 7. Thick forest or areas involving heavy compensatory payments for acquisition of land etc. 8. Buildings containing explosives, bulk storage oil tanks, oil or gas pipe lines, etc. 9. Aerodromes, helipads, etc. The reconnaissance survey is also essential for collecting the first hand account of various important field data required for transmission line works, which are as under: 1. Major power line crossing details (66 kV and above)
2. Railway crossing details. 3.
Major river crossing details.
4. Source of construction materials, viz .• metal, sand, water etc., along the line. 5. Important rail heads for the purpose of receipt of materials. 6. Important villages or stations coming enroute for the purpose of selection of labour camps. 7. Nature of soil strata along the route and the terrain. 8. Availability of labour, their present rate on daily basis or on contract basis. 9. Names of the major towns for the purpose of selection of site offices. For fixing the final alignment and angle points on the ground as per the reconnaissance survey, route alignment survey shall be carried out with a theodolite, survey chains/ measuring tapes/electronic distance measuring instruments.
115.1.2 Detailed Survey The object of carrying out detailed survey is to prepare longitudinal and cross section profiles on the approved alignment and to prepare the route plan showing details of deviation angles, important objects coming within the right of way. General Considerations Work of detailed survey is distinctly done in two stages: 1.- Actual field observations taking level readings andl) calculating distances, level differences, deflection angles, offset distances etc.
6 - - - - - - - - - - - - - - - - - ------------
----
2. Plouing of profiles on graphed uacing papers. 11.5 .1.2.1 Field Observalion Recording and Calculalions The method of taking level readings for preparation of longilUdinal and cross section profile can be 1. By chain and dumpy level. 2. By tacheometric survey with theodolite. First method is very useful in plain areas where chaining offers no problems. This also requires comparatively less skilled surveyors. Tachcometric method offers a great advantage in hilly regions and such other inaccessible places where chaining is nol possible. This method needs skilled surveyors having good understanding of the use of theodolite. In this method, both traversing and levelling is done by means of a tacheometric theodolite (theodolite having stadia cross hairs fitted in the eye piece). The horizontal and vertical distances are computed by the help of readings of the stadia wires taken on the staff held at the reading station. For the theory of this method reference may be made to any standard surveying text-books. The above two methods are best explained by means of a worked example of filling field books and calc ulations thereof in Annexure-' B' of this chapter. 11 5.1.2.2 PlOlling of Profiles From the field book entries route plan and longitudinal profile, commonly referred to as 'Survey chart' is prepared in the drawing office. These charts are prepared and plotted Qn 1 mmlS mm/l em square paper of formed drawing sheets of graphed tracing paper, which are available for this purpose to a scale of 1:200-vertical; 1:2000-horizontal. These shall show: 1. The longitudinal profiles along the centre-line of the uansmission line route.
2. The cross-section profile wherever appreciable difference jn level exists with reference to centre-line level. In such cases the cross-section levels shall be taken at each 50/100 m intervals.
3. Route plan giving details of all objects lying within the right of way. 4. Angle ofline deviation duly marked left (L) onight (R) as the case may be. Following general considerations apply in the preparation of the survey charts: 1. Objects and their distances along the route within the right of way from centre line, nearby villages, important roads or rivers should be marked on the route proflle.
2. Cr~sin.ifetails with.any o~er power or te~ecommuni cauon lilies, roads, railway lines, ~als or nvers should - - - _-'_'1_
Construclion of Transmission Lines
3. Readings should be taken and charts should show, levels of roads, canal embankments, maximum waterl flood levels, railway top levels, heights of supportsl lines being crossed, all trees coming within the clearance zone. One typical example of Survey Chart/Profile duly plotted with tower locations is shown in Annexure-'C'. 115.1.3 Tower SpOiling The work of tower spolling is clearly divided into the following five operations: 1. Sag tension calculations. 2. Preparation of Sag Template. 3. Application of Sag Template to decide optimum tower position on Survey Chart. 4. Preparation of Structure Limitation Charts. 5. Deciding tower type and preparation of Tower Schedule. 11 5.1.3.1 Sag Tension Calculations The span length i.e. distance between two adjucenttower locations is fixed at an optimum level by consideration of various factors like line voltage, ground clearance, topography of the area, conductor used, wind, ice and temperature conditions, availability and cost ofline materials and over all project economy. A detailed discussion on this aspect is beyond the scope of present study and it will suffice to assume that the optimum span length for the line is fixed by the purchaser. This optimum span is called the "Basic Design Span" and forms the basis of all calculations to develop a suitable tower design for the line. Aconductor suspended freel y between two supports takes the shape known geometrically as "catenary" . TIle dip from the centre point joining the two supports called' Sag' being inversely proponionalto the tension in the conductor at null point. For all practical purposes the 'catenary' can well be simplified as a 'Parabola' without much error. In case higher accuracy is desired in finding the sags (particularl yin case oflonger spans) a catenary correction can be applied. For detailed discussion on the shape of catenary and parabola, and catenary correction . reference may be made to any standard text book on this subject. Since weight of tower supporting the conductor and consequently its cost depends upon its height, the tower is designed for a minimum height which is equal to the maximum sag at design span (at the maximum anticipated temperature) plus the minimum ground difference required between the charged conductor and ground as per Indian Electricity Rules. Maximum sag at design span is governed by maximum tension that can be given to the conductor which in tum depends upon the external loading of wind, ice and tempera-
-,
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physical properties of the conductor used. Moreover, from me considerations of safety of electric installations, Indian Electricity Rules demand a minimum factor of safety to be maintained in tensioning the conductor. All these factors are checked during 'Sag Tension Calculations' which fixed the maximum tension and maximum sag to be taken for design of tower and stringing of conductor. For detailed calculations reference may be made to Chapter VI "Loading" of this manual.
The 'Cold and Hot' Template Curves are ploued as parabola, to the same scale as the survey chart for the minimum and maximum sags for the ruling span (nonnal design span being considered as theoretical ruling span).
Application of Sag Template for Tower Spotting The Sag Template is applied to the profIle by moving the same horizontally while always ensuring that the vertical axis 115.1.3.2 Preparation of Sage Template is held vertical. The structure positions are marked where the Sag Template is a very important tool for the surveyor by tower footing curve cuts the profile, while the ground clearthe help of which the position of tower can be decided on the ance curve is just clear and above the proflle. The ground Survey Chart so as to conform to the limitations of specified clearance curve shall not onl y clear the route centre line profile minimum ground clearance required to be maintained as per but also the proflle to the left or right of the centre line upto a I.E. Rules, between the line conductor to ground telephone distance equal to maximum cross area spread on either side. lines, buildings, streets, navigable canals, power lines, or any Besides normal ground clearance, the clearance between power other object coming under or near the line and the limitation of conductor and objects like, other power or telecommunication . lines, houses, trolly wires, roads, railway tracks, canal emvertical load coming on any particular tower. bankments etc., shall be checked. Extra clearance can be got Sag Template consists of a set of parabolic curves drawn on a transparent paper, a celluloid or acrylic clear sheet duly cut either by reducing the span or providing extension to tower body depending on which alternative is most economical. The in between the curves to allow surveyor to see through them on weight span on either side of a tower can be easily obtained by the Survey Charts placed underneath it. The set of curves marking the low points of sags in two adjacent spans and then consist of: reading the distance between the two. On inclined spans, null 1. 'Cold or Uplift Curve' -Showing sag of conductor at point may be outside the span. This indicates that the total minimum temperature and still wind. weight of conductor is taken up by the higher,tower and the 2. 'Hot' or 'Maximum Sag Curve'-Showing maximum lower tower is being pulled up by a force equal to the weight sag of conductor under still air and maximum temperaof conductor between lower support and the null point.(!ould ture and still whid including sag tolerances allowed if the upward pull of the uphill span becomes greater than any or under maximum ice condition. downward load of the next adjacent span, actual uplift will be 3. Ground clearaIl;ce Curve-Drawn parallel to curve (2) , caused and the conductor would tend to swing clear of the and at a distance equal to specified minimum ground lower upwardj]For an easy check of whether a tower is under uplift or not, the following method may be adop,ted. The clearance. Template is applied horizontally until the tops of alternate 4. Tower footing Curve-For normal tower drawn parallel supports coincide with the Cold Curve. If the support is under to curve under (3) above and separated by a distance uplift and has to be extended so as to be above it and in case equal to maximum sag at design span. requisite standard body extensions do not suffice for doing A typical' Sag Template' drawing is shown in Annexurethis, a tower which is designed to take uplift will have to be '0' used. However, for the stability of the line it is nol desirable to In erecting an overhead line all the spans cannot be kept place a tower in such ~sition where it is always under equal because of the profile of the ground and proper clearance permanent uplift condiilimJ considerations. A constant tension is calculated which will be The intermediate spans shall be as near as possible to the uniform throughout the Section. For calculating this uniform normal'design'span. In case an individual'span becomes too tension an equivalent span or ruling span for the whole section short on account of undulations in ground profiles one or more of the line is chosen. The ruling span is then calculated by the line supports of the Section may be extended by inserting following formula. standard body extensions.
LU=
~ L,'+ 1.,' + 1.,' +.......... LI + Lz + L) +..........
Where LU =ruling span Lp Lz' L) ................. etc are different spans in a section.
115.J.3.3
In other countries longer stretches of transmission lines in straight run are constructed without Section towers. In India Sections towers may be provided after every 15 tangent towers. To be in llne with the construction practices in other countries this aspect needs review in future.
8
Construction of Transmission Lines
Structure Limitation Charts/Towers Spoiling If the sum A and B calculated for a particular tower is Data negative. the tower is under 'uplift'. Since each tower is designed to withsland a definite load Maximum weight span is obtained under the conditions of only in each of transverse. vertical and longitudinal directions, . minimum temperature and no wind. the surveyor must know these limitations for the various types . of towers available for use on line. These limits are given in a 115.1.4 Check Survey Objecl-Check survey is carried out for the following chart form called 'Structure Limitation Chart' or 'Tower Spouing Data' which is prepared by the design department (i) To reconfirm the work carried out during detailed These charts define the limits for permissible ruling span, survey. weight span. wind span. individual span and the degree of line (ii) To locate and peg mark the tower position on ground deviation allowed on each tower. These charts are made for controlling to the route profiles. Donnal towers only. For all special crossings individual tower (iii) To give direction pegs. checking is essential by the design department. Specimen Tower Spotting Data is shown in Annexure-'E'. A. Checking and Line AUgment In this operation traversing is done from the known fixed 115.1.35 Deciding TowJr Type and Preparation of angle poinl (the starting poinl or any other obligatory point Tower Schedule flXed by the purchaser) in the direction of given line deviation In order to decide the tower type for a particular location . and upto a distance equal to the Section length between the following information is required: starting point and the next angle point If this next angle poinl Angle of line deviation on tower. is firmly marked in field by means of a permanent peg mark (or
115.1.3.4
Whether it is to be used as section tower or dead end tower Sum of adjacent spans Weight span on tower For proforma Tower schedule. Annexure-'F' may please be referred to. 11 5.1.35.1
Weight Span The analytical method for calculating weight span is given below. Distance of "Null point" or "Low point" of conductor from centre of span is given by formula (see Figs. 1 and 2) T
h
X= - X w I
Where X = distance of low point from centre of span in m T =conductor tension in kg. h =difference between conductor support levels in m w = unit weight of conductor in kg/m, and I =span length in m Weight Span For tower A. right h~d side Qnly 1 a= - - X
2
For tower B. left hand side only b= _1 +X 2 t"!-...!1 __ 1.........
_~_L&
___ "r __ aL __ .. L ___ !..J __ r .. L _ .. _________ _
concrete burjee) then the closing error is noted both in longitudinal and transverse direc tions.1f the error is within 1%of the total Section length it can be ignored and the permanent mark made during detailed survey is taken as correct and necessary correction in the line deviation angle at the starting point is made and noted in the survey chart If the second angle poinl reached is not marked in field by the detailed survey gang (or the mark is missing) the angle. point is tentatively fixed at the place reached as per deviation angle at starting point and first Section length and line aligmenl proceeded to the next'deviation angle and next Section length as per Survey Chart. This process is continued till an angle point is reached which is fixed in field either by permanent burjee or by means of identification marks given in Survey Charts. Intermediate checks can also be made by measuring offsets from the line to well defined objects shown in Survey Charts very accurately (but much reliance cannot be given for correct alignment based on offset distance). These objects only guide the surveyor in moving as closely on the correct alignment as possible. Once the known angle point is reached then the closing' error is judiciously distributed in all the previous temporary Sections and all angle points are finally marked on ground by means of concrete pillar. Once the angle points are marked. correct angle of deviation and Section length are measured and noted on Survey Charts. Any adjustment in Section length is normally done in the last span of that section or in that span where very marginal clear8I1ce was kept at the time of tower spouing (if reduction is required) or where enough clearance is available (if increase is required). B
Spotting and Peg Marking o/Tower Locations
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concrete burjces and exact Section length is known, the surveyor proceeds to mark all intcnnediate tower positions on the straight line joining the 2 angle points spaced at a distance equal to individual span length as given on Survey Chan and after the same is duly adjusted for the closing error.
should be obtained alongwith a true assessment of problems facing procurements of right of way.and way leaves for access and compensation required to be paid after evaluation of the val ue of the damaged crops and vegetation wi th the help of the Revenue Authorities.
In order to help in correct aligning all intermediate lOwers between 2 angle points, a number of aligment pegs are given at the time of exact distance measurement of the Section. The more the number of alignment pegs the better it will be for the readings a" instrument errors are less if smaller distances are measured in one reading. These pegs are also very useful when main tower marking burjccs are found missing at a later dale (due lO mischief of local people or negligence of excavation marking gang).
The following right of way widths for different voltages of power lines are recommended
C. Directional Peg Marking for Excavation Pit Marking Directional pegs are es~ential for correct alignment of tower centre line along longitudinal and transverse directions. On suspension tower, pegs are set along the centre line of route alignment and perpendicular to it. On angle towers these are rotated by an angle equal to half the angle of line deviation. 11.5.2 Various survey techniques, depending upon the field conditions, type of towers and available time frame are used in different countries. Modern methods like Satellite Doppler Technique, Orthophoto Mapping used in many othercountriesarediscussed in Appendix -'A' . 11.5.3 Clearing of Right of Way Having decided on the choice of the route, it is necessary to see right of way before commencing construction work. Information of forest land, cultivated fields, orchards etc.,
SI
Transmission Voltage
No
Recommended width of Right of way in metres
1.
66KV
18
2.
llOKV
22
3.
132KV
27
4. 5.
220KV 400KV
35 52
6.
±500 KV
52
HVDC 7.
800KV
85
11.5.4 Tolerance The accuracy of survey workdepends upOn, the accuracy of surveying instruments, the prevailing temperatures, the accuracy of placing instruments and their readings. It shall be ensured, however, that no measurement should be missed during surveys and the survey shall be checked where any doubt arises. In transmission line surveys where the linear measurements are carried out using an Engineers' chain overrough ~d uneven ground the expected accuracy is between 1 in 200 to 1 in 250.
10------1 ...
~t---l - -.. .-.tl
I 1 h
h
Low or
Low.or
null point
null point
.......- - e
t - - - - b - -.....
..---I/2 - -.......--112 - ........
I---+--
b
t-II2
Figure 1: Distance of Null Point or Low Point from (entre Point
-I
I/2---f
Figure 2: Distance of Null Point or Low Point from (entre Point
Construction of Transmission Lines
10
n.6
FOUNDATIONS
n.6.1 Trpe of Foundations The different types of foundations adopted in practice depending on the soil or combination of various types of soils encountered at various locations, their advantages, usefulness and method of construction are described in details in chapter X. However, the same are brought out for ready reference in a nutshell hereunder. 11.6.1.1 Chimney and Pyramid Type This is shown in Annexure-'G' (Figure I). These are used in normal type dry and cohesive soils having clay percentage of 15 to 30. Form boxes are required to cast this type of foundations. These are generally P.C.C. type foundations. 11.6.1.2 Block Type This is shown is Annexure- 'G' (Figure 2). These are used in soft rock and hard rock foundations. Proper care has to be taken to see that the concrete is poured in direct contact with the linner walls of the excavated rock. 11.6.1.3 Under Cut Type This is shown in Annexure- 'G' (Figure 3). Foundations of this type are very useful in non-cohesive type of soils like hard murrum, Soft murrum, fissured rock, clincker mixed soil. However, the latest trend is to cast these foundations in nonnal dry soil 100 because of certain advantages. 11.6.1.4 Spread Footing Type This is shown in Annexure-'G' (Figures 4 & 5). These foundations can be either step type or chamfered type. These are generally used in wet submerged nonnal and submerged black cotton soils. 11.6.1.5 Anclwr Rod Type This is shown in Annexure-'G' (Figure 6). These foundations are suitable for hard rock strata. The advantage of this type is the reduced depth of foundation. 11.6.1.6 Auger Type/Under Reamed Type This is shown in Annexure-'G' (Figure 7). These foundations will be useful in case of clayee and firm soils. However, these types of foundations are not popular in transmission lines. 11.6.1.7 Steel Plated Type This is shown in Annexure-'G' (Figure 8). These will be useful only in case of good cohesive and firm soils where head loading and mixing is a problem (but not hilly terrain). These type of foundations are not very popular for the normal run of the line. 11.6.1.8 Grillage Type This is shown in Annexure-'G' (Figure 9). These will be II~A
nnlv in firm C!nilC! whp..,. !lnnrn!ll'hpC! !lrp!l nrnhlprn Th .." ..
are also not very popular in this country.
11.6.1.9 Well Type This is shown in Annexure-'G' (Figure 10). These will be useful in case of submerged locations, river beds and fully sandy strata. 11.6.1.10 Special Pile Type This is shown in Annexure- 'G' (Figure 11). These foundations will be very useful in river bed and creek bed having constant flow of water and sea mud to a large depth. In shallow depth, precast driven piles can also be useful. In marshy soil, the foundation can also be rested on the wooden piles driven in the soil. If there is solid rock below the river/ creek bed the pile can rest on it. 11.6.2 Levelling of Tower Site, Benching, Revetments and Hill Side Extensions
11.6.2.1 Levelling of Tower Site, Benching and Revetments The location site is normally divided into a number of grids of 3m x 3 m and the reduced levels at the all intersection points are taken with respcctto centre peg of the locations to ascertain the volume of benching/filling that will be required to level the tower site. The tower site is to be levelled by cutting the excess earth and filling the down area and is to be brought to the centre peg level of the location. A retaining walV revetment is to be constructed to avoid the washing out of retainer earth. Normally a revertment is constructed upto a height of 15 cm higher than the centre peg level of the location. 11.6.2.2 //ill Side Extension In hilly areas where for spotting the locations heavy benching or revetment or both are involved, for normal tower as well as tower with extensions suitable hill side extensions ranging from 2m to 6mcan be used. A sketch of a typical hill side extension is shown in Annexure- 'H'. 11.6.3 Excavation
11.6.3.1 Pit Marking Pit marking shall be carried out according to pit marking Chan. The pit size in the case of open c.ut foundation shall be determined after allowing a margin of 150mm all round. No margin is necessary in the case of under cut foundations. The depth of the excavation at the pit entre shall be measured with reference to the tower centre level. The design office will furnish the survey gang with an 'Excavation pit Marking Chart' or 'Excavation Plan' (Annexure- 'I') which gives distance of pit centres, sides and corners with reference to centre point of the tower. These distances are measured and each pit boundary is marked in the field by means of spade or pick axe along the side of the pits. While excavating care should be taken that earth is cut vertically/tappered/in steps as per the site requirement to avoid any
" " .V •..!.~ UfiVI
"'6 UflU lJflUUCf "'~
In pits excavated in sandy soil or water bearing strata and particularly black cotton soil where there is every likelihood of pits collapsing, sharing and shuttering, made out of timber planks 30-35mm thickness or steel frames of adequate strength to suit the requirement, will be provided. Sand bedding/stone bedding will be provided in foundations of marshy and Wet Black Cotton foundations.
11.6.3.3 Dewatering Dewatering shall be carried out manually or by mechani-cal means or power driven pumps to facilitate excavation and casting offoundation. The pumps shall be suitable for handling mud water. Dewatering is not necessary in case of bored foundations extending below water table. In areas where sub-soil water recoupment is heavy and where water cannot be controlled even by use of power driven pumps well point system is used for controlling water. In this system a grid of pipes are laid around the area where the pits are . excavated and the system is very effective in pumping water particularly in sandy soils. After commencing pumping operation the pit can be excavated avoiding risk of collapse of earth. This will ensure proper quality of concreting. Another method is by drilling bore holes of a deeper pit much below foundation level for pumping out water by ordinary pumps. Number of bore holes depend on the volume of sub-soil water. In areas where sub-soil water recoupment is very rapid and water can not be controlled 'shallow foundations' will be useful. 11.6.3.4 Excavation in Rock , For excavation in hard rock, blasting can be resorted to. Reference shall be made to statutory rules for blasting and use of explosives for this purpose. No blasting is permitted near ' permanent work or dwellings. Blasting shall be so made that pits are excavated as near to the designed dimensions as practicable. The work of blasting in rock is carried out in three separate operations: (a) Drilling of holes to hold explosive charge (b) Charging of the drilled holes (c) Fixing the charge 11.63.4.1 Drilling of HoLes to HoLd ExpLosive Charge Drilling ofholes to hold the explosive charge may be done either manually or with an air compressor as per the requirement at the site. The equipment for hand drilling is simple but requires more man hours and generally consists of a set of' Jumpers' or 'Drills' which are usually made from 22mm diameter hexagonal steel bars.
IneJumpersare 1m. l.l)mand 1.5mlongandaresuitably shaped. They must be tempered when sharpened. A 2 kg hammer is used for striking the jumper, which is given a slight rotation after each blow. The rate of progress by this in hard rock is 25 to 40cm per hour. When large quantity of rock is required to be excavated, an air compressor is used for drilling the holes.
11.6.3.4.2 Charging of the Drilled Holes The charge consists of gelatine and detonator. Either half or a full gelatine' is used as per the requirement. Detonator is normally pressed into the gelatine after making a hole in the gelatine with a stick. Detonator is to be pressed into the gelatine till it is completely embedded in the gelatine. Then this assembly is placed into holes drilled. 11.6.3.4.3 Fixing the Charge The detonator leads are first interconnected to form a circuit and later the ends of this circuit are connected to the exploder with separate wires. The exploder is kept in a sheltered spot To fire the shot the exploder handle is rotated at a high speed. 11.6.3.4.4. Procedure in Case of Misfired Shots (a) The misfired shot should not be touched. (b) One should not approach a misfired shot until atIeast 15 minutes have elapsed and all connections and handle removed from the exploder. (c) A second hole is to be drilled at a safe distance from the first and in such a direction as will keep the boring tool clear of the first hole. (d) This second hole is to be charged and fired: (e) The debris ,is to be searched thoroughly for unexploded ' detonator and gelatine. 11.6.3.4.5 Additional Precautions To protect the persons and animals from injuries from flying debris depending on situation the number of holes to be drilled should be less deep and the pit should be covered with a steel plate. Such controlled blasting is an exception if the transmission line is kept away from villages and inhabited areas. Usual precautions for safety of working personnel are taken in all cases. ' 11.6.4 Soil Investigation and Classification of Foundation The transmission tower foundation shall be classified based on-the soil conditions. Optimisation offoundation design and their safety mainly depend on correctness of soil and their analysis.
11.6.4.1 Soilinvestigation il;' The scope of work includes detailed soil investigation at' various tower locations such as railway crossings, major road /J .
I'
Construction of Transmission Lines
12 crossings. power line crossings. river crossings and wherever soil strata differs. However. the soil investigation activities shall be .completed alongwith preliminary survey much before the coinmencement of main erection activities. Soil investigation need not be carried out in all the locations of the line. 11.6.4.1.1 Soil Investigation at Normal Locations One bore hole of 150mm dia shall be drilled at the centre point of the tower. Standard penetration test (S.P.T.) shall be carried out at 1.5m interval or change of strata upto the required depth of 21 times below the depth of foundation below existing s~ce elevation or refusal whichever occurs earlier. (B y refusal it shall mean that a standard penetration blow count 'N' of 100 is recorded for 30cm penetration). Bore details and water table upto required depth below existing surface elevation or refusal whichever occurs earlier shall be furnished in the reporl 11.6.4.1.2 Soil Investigation at Special Locations At certain locations such as rivers banks, river beds or midstream of river and at other places. special soil investigation shall be carried out by drilling two holes each of 150mm diameter at each lOwer location on the diagonally opposite legs of the tower. considering the base width of tower as 20m. Standard penetration tests shall be carried out at every 1.5m interval or change of strata till refusal is met subject to maximum of 40m below the existing surface elevation. Undisturbed samples of soils shall be collected at every 2.5m interval or change of strata whichever occurs earlier. In the hard rock the bore drilling shall be continued atIeast 5m to ascertain its sufficient thickness.
i
11.6.4.1.3 Preparation of Test Reports The investigation report shall contain the following test results: 1. Grain size analysis 2. Nomenclature of soil 3. Atterbergs limit (Liquid and plastic limit only) 4. Triaxial shear Test results containing information about angle of internal friction and cohesion. 5. S.P.T. results containing information about natural moisture content. Specific gravity and Bulk unit weight. 6. Consolidation tesl 7. Unconfined compression test 8. Unconsolidated undrained test 9. "Presence of carbonates. sulphates. nitrates and organic matters and any other chemicals harmful to the concrete foundatiolH>btained from chemical test on soil sample. 10. For rocky, soil core recovery and crushing strength of the
II. The bearing capacities of soil at 3. 4 & 5m below the existing surface elevation for normal investigation and at 3,6 & 9m below the existing surface elevation for special soil investigation shall be furnished considering approximate base width of foundation. In addition to the above the following data also shall be furnished in the report of Special Soil Investigation. 1. Scouring depth in case the locations are at the bank of river or at midstream. 2. Silting factor in case of midstream and river bank locations where submergence is envisaged. 3. Depth of fill. if any. 4. Details of water table, water struck etc. 5. Compressibility of sub-soil stratification. " 6. Settlement characteristics of the shallow foundations. The above test results shall be summarised strata-wise as well as in a combined tabular form with all relevent graphs, charts, tables, diagrams and photographs, if any, shall be furnished in the test reports. The test report shall include bore logs. Bore logs of each bore hole clearly identifying the stratification and type of soil stratum with depth upto the refusal. The locations of water table shall be identified in the bore log. The value of SPT at depth where conducted and various laboratory tests conducted from samples collected at various depths shall be clearly shown against the particular stratum. The report should contain specific recommendation for the type of foundation. In case the soil parameters obtained from the soil investigation report for a particular lOwer location, differ from the ones considered during design, a fresh design has to be developed for such locations.
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11.6.4.2 Classification of FoundaJions Classification of soil shall be made according lO IS : 200 (part 1) 1974 for footing cast in open pits.· The foundation designs shall depend upon the type of soil. sub-soil water level and the presence of surface water which have been classified as follow. 11.6.4.~.l
No_rmal Dry
To be used for locations where nonnal dry cohesive or non-cohesive soils are mel
11.6.4.2.2 Wet To be used for locations (a) Where sub-soil water is met at 1.5 metres or more below the ground level. (b) Which are in surface water for long periods with
water penetration not exceeding one metre below the
11.6.4.2.3 Partially Submerged To t>e 'used at locations where sub-soil water table is met between 6.75 metre to 1.50 metre below the ground level. 11.6.4.2.4 FullySubmerged To be used at locations where sub-soil water table is within 0.75 metre below the ground level. 11.6.4.2.5 Black Colton To be used at locations when soil is clayey type, not necessarily black in colour, which shrinks when dry, swells when wet, resulting in differential movement extending to a maximum depth of about 3.5 metres below ground level. 11.6.4.2.6 Fissured Rock To be used at locations where decomposed or fissured rock, hard gravel, kankar, limestone, laterite or any other soil of similar nature is met. Under cut type foundation is to be used for fissured rock locations. Rock anchor type foundation can also be used for fissured rock location where the under cut is not feasible. In case of fissured rock locations where water table is met at 1.5 metre or more below ground level submerged fissured rock foundations shall be adopted. When the water table in such location is met within 1.5 metre from ground level, fully Submerged Fissured Rock type foundations shall be adopted.
;~
...
11.6.4.2.7 Hard Rock The locations where chiselling, drilling and blasting is required for excavation, hard rock type foundations are to be used. For these locations rock anchoring is to be provided to resist uplift forces. 11.6.4.2.8 In addition to the above, depending on the site conditions other types of foundations may also be developed for: 1. Intermediate conditions under the above classifications to effect more economy or 2. For locations where special foundations (well type or piles) are necessitated. While classifying foundations of Wet, Partially Submerged, Fully Submerged foundations mentioned above, the worst conditions should be considered and not necessarily the conditions prevailing at the time of inspection. For instance. there are areas where sub-soil water rises when canal water letout in the fields raising sub-soil wa~r to a considerable degree. Simifarly the effect of monsoon or when the nearby reservoirs are full should also be considered and not the conditions prevailing in open season or summer when work is carried out normally. 11.6.5 Stub-setting The stubs are set in such a manner thai the distance between the stubs and their alignment and slope are as per
design so as to perm it assem bling of the superstructure without undue strain or distortion in any part of the structure. There are three methods by which this is generally accomplished. (i) Use of a combined Stub-setting Template for all the four stubs of the tower. (ii) Use of Individual Leg Template for each stub. (iii) Use as a Template the lower tower section or extension, where Stub-setting Template is not available. The first method is the most commonly used. The Stubsetting Template is composed of a light rigid framework which holds the stubs at the correct alignment and slOpe. The Stubsetting Template is generally of adjustable type which can suit the standard tower as well as towers with standard extensions: The Template is centred and levelled by sighting through transit The anchors or slubs are bolted to this Template, one at each comer of the Template, and are held in their proper position until the concrete is poured and has hardened. The procedure for setting stubs at.site is given in Annexure- 'J'. The second method is adopted for casting the foundation 'locations having individual leg extensions or locations having broad base for which use of a single Template for setting all the four stubs is unwieldy. The Individual Leg Template comprises a steel channel or joist having a length more than the size of the pit. by about 2 to 3 metres. A chamfered cleat is welded in the centre of the channeVjoist to provide the slope to the stub. The stub is bolted to the cleat of the Template for which holes as required for the slope of the stub are provided. The Individual Leg Templates are initially seton each pit approximately to the' required position w.r.t. the centre point of the tower and after that stubs are bolted to the cleat The stubs are then brought to proper position w.r.t. the centre of the tower with the help a Theodolite, Dempty level and a measuring tape, before fixing form boxes and pouring concrete. This type of Templates are very useful for casting the foundations of individual leg extensions in which the foundation pits are staggered and use of either a normal Stub-setting Template or the first section of the tower is not feasible. The foundation layout of unequal leg extensions is shown in Annexure- 'K' In the third method, lower section of the tower or extension is used for setting stub. In this method two opposite sides of the lower section of the tower are assembled horizontally on the ground, and the stubs are bolted to the same with correct slope and alignment. Each assembled side is then lifted clear of the ground with a gin pole and is lowered into the four pits excavated at four comers of the tower to their proper size and depth. The assembly is IifWEI in such a manner that stubs are not damaged. One side is held in place with props while the other side is being erected. The two opposite sides are then laced together with cross members and diagonals. Then the aSsembled section is lined up. made square with line and levelled. The propereJevation an~.levelling are done with a transit. When the
I Construction of Transmission Lines
J
The fOnTI work for slabs and pyramids shall be made symmetrical about the bases of the chimney to ensure interchangeable faces.
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14 lining and levelling has been done, the bolts are tightened up to make the frame as rigid as is reasonably possible. Thereafter the fonn boxes for foundations are built and the concrete is poured. For heavy towers use of Stub-setting Template is recommended.
11.6.6 Concreting
11.6.6.1 Type For reasons of economy and progress it is nonnal practice to use coarse and fme aggregates available along the line route and/of nearest locations to the route. Ordinary plain or reinforced cement concrete given in IS: 456-1978 shall be used in overhead line foundations.
11.6.6.2 Mixes For main foundation, M 15 or 1:2:4 mix cement concrete shall be used. For lean concrete sub-bases or pads, M 10 or 1:3:6 mix cement concrete may be used. The properties of concrete and mix proportions shall be as given in IS :456-1978. It shall be pennissible to proportionate the concrete as follows. 11.6.6.2.1 Prepare a wooden measuring box of 35litres capacity (that is equal to 1 bag of 50 kg. of cement) with inside dimensions of 30cm x 30cm x 39cm alternatively a cylinder of 34cm diameter and 39cm height. The mix quantities according to the measuring box shall be as follows:
MIO Cement 1 bag 2 boxes Sand 3 boxes Metal 4 boxes 6 boxes Water 1 boxes less 3 litres 1box less 1 litre 11.6.6.2.2 Measurement of water may be made with separate water tight drwns of the above size or with 1 or 2 litre mugs. 11.6.6.3 One bag of cement is taken to contain 50 kg or 35 litres of ordinary portland cement MIS 1 bag
11.6.7 Form Work 11.6.7.1 General The fonn work shall confonn to the shape, lines and dimensions as shown on the foundation design drawings, and be so constructed as to be rigid during the placing and compacting of concrete, and shall be sufficiently tight to prevent loss of liquid from concrete. It shall be of light design, easily removable without distortions and shall be of steel or suitable materials. The inner surface coming in contact with concrete shall be smooth and free from projections. Window on one face shall be provided for pyramid fonns to facilitate concreting in the lower parts which shall be flxed after concrete in the bottom
11.6.7.2 Clearing and Treatment of Forms All rubbish, particularly chippings, shaving and sawdust and traces of concrete, if any, shall be removed from the interior of the fOnTIS before the concrete is placed. The surface in contact with the concrete shall be wetted and sprayed with fine sand or treated with an approved composition such as black or waste oil etc., before use, every time. 11.6.7.3 Stripping Time Under fair weather conditions (generally where average daily temperature is 20 degree or above) and where ordinary cement is used, fOnTIS may be stripped after 24 hours of the placing of concrete. In dull weather such as rainy periods and very cold temperature, the fOnTIS shall be removed after 48 hours of the placing of concrete. 11.6.7.4 Procedure when Removing Form Work All fOnTI work shall be removed without much shock or vibration as otherwise it would damage the concrete or the fonns. 11.6.8 Mixing 11.6.8.1 Concrete shall preferably be mixed in a mechanical mixer, but hand mixing shall be pennissible. 11.6.8.2 When hand mixing is adopted, it shall be carried out on impervious platfonns such as iron plain sheets properly overlapped and placed upon level ground. The coarse aggregate shall first be evenly spread out in required quantity over the sheets. The flne aggregate shall be evenly spread out over coarse aggregate next. The aggregates shall then be thoroughly mixed together and levelled. The required amount of cement shall now be spread evenl y over the mixed aggregates and wet mixing shall start from one end with required amount of water using shovels. The whole lot shall not be wetted; instead mixing shall proceed progressivel y. If the aggregates are wet or washed, cement shall not be spread out, but shall be put in progressively. 11.6.8.3 For mixing in mechanical mixers, the same order of placing ingredients in the loader drum shall be adopted, that is coarse aggregate shall be put in fIrst followed by sand, cement and water. 11.6.8.4 Mixing shall be continued until there is a unifonn distribution of materials and the mass is unifonn in colour and consistency but in no case shall mixing be done for less than 2 minutes. 11.6.8.5 If the aggregates are wet, the amount of water shall be reduced suitably. 1UiJj
Tr.llmmortation
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dation. In places where it is not possible, concrete may be mixed at the nearest convenient place. The concrete shall be handled from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the segregation or loss of any of the ingredients. If segregation does occur during transport, the concrete shall be remixed before being placed. 11.6.9.2 During hot or cold weatherw concrete shall be transported in'deep containers. The deep containers, on account of their lower ratio of surface area to mass, reduce the rate ofloss of water by evaporation during hot weather and loss of heat during cold weather. 11.6.10 Placing and Compacting 11.6.10.1 The concrete shall be placed and compacted before seuing commences and should not be subsequently disturbed. The placing should be such that no segregation takes place. 11.6.10.2 Concrete shall be thoroughly compacted during the placing operation, and thoroughly worked around the rein. forcement, if any, around embedded fixtures and into comers of form work by means of 16mm diameter poking bars pointed at the ends. As a guide for compacting, the poking bars may be worked 100 times in an area of 200mm square for 300mm depth. Over compacting causes the liquid to flow out upward causing segregation and should be avoided. 1l.6.10.3 If, after the form work has been re!lloved, the concrete surface is found to have defects, all the damaged surfaces shall be repaired with mortar application composed of cement and sand in the same proportion as the cement and sand in the concrete mix. Such repairs shall be carried out well before the foundation pits are back filled. 1l.6.10.4 For precautions to be taken on concrete work in extreme weather and under water, the provisions of ~S : 456 : 1978 shall apply. 11.6.11 Reinforcement All reinforcement shall be properly placed according to foundation design, drawing with a minimum concrete cover of 50mm. The bars shall, however, be placed clear of stubs and cleats where fouling. For binding, iron wire of not less than 0.9mm shall be employed, and the bars may, be bound at alternate crossing points. The work shall conform to IS : 25021963 wherever applicable. In case of the foundation having steel reinforcement in pyramid or base slab, atleast 50mm thick pad of lean concrete of 1:3:6 nominal mix shall be provided to avoid the possibility of reinforcement rod being exposed due to unevenness of the bottom of the excavated pit. 11.6.12 Sizes of Aggregates The coarse aggregate (stone/metal) to be used shall be 40mm nominal size for slab/pyramid concrete and 20mm nominal size for chimney concrete conforming to IS: 3831979. These sizes are applicable to ordinary plain cement
concrete. For R.C.C. works the aggregate shall preferably be of 20mrn, ,nominal size. The fine aggregate (sand) shall be of preferably Zone I Grade to IS : 383-1979 which is the coarse variety with maximum particle size of 4.75mm. 11.6.13 Levelling Sub-base To take care of the unevenness at the bouom of the excavated pit it is necessary to provide a levelling sub-base not less than 1:3:6 proportion and 50mm thickness. 11.6.14 Back Filling, Following opening of form work and removal of shoring and shuuerings back filling shall be started after 24 hours of casting or repairs, if any, to the foundation concrete. Back fill ing shall normall ybe done with the excavated soil, unless it· consists of large boulders/stones, in which case the boulders shall be broken to a maximum size of 80mm. The back ruling materials should be clean and free from organIc or other foreign materials. The earth shall be deposited in maximum 300mm layers, levelled and wetted and tamped properly before another layer is deposited. Care shall be taken that the back ruling is started from the foundation ends of the pits towards the outer ends. After pits have been back filled to full depth, the stub-setting template may be removed. The back filling and grading shall be carried out to an elevation of about 75mm above the finished ground level to drain out water. After back filling 50mm high earthen embankment (bund) will be made along the sides of excavated pits and sufficient water will be poured in the back filled earth for atleast 24 hours. 11.6.15 Curing The concrete after setting for 24 hours shall be cured by keeping the concrete wet continuously for a period of io days after laying. The pit may be back filled with selected earth sprinkled with necessary amount ofwater and well consolidated in layers not exceeding 300mm. after a minimum period of 24 hours and thereafter both the back ruled ~ and exposed chimney top shall be kept wet for the remainder of the prescn'bed time of 10 days. The uncovered concrete chimney above the back filled earth shall be kept wet by providing empty cement bags dipped in water fully wrapped around the concre.te chimney for curing and ensuring that the bags be kept wet by the frequent pouring of water on them. 11.6.16 Tolerance The tolerances for various items connected to the found8tion works of transmission line are as under.
11.6.16.1 Stub-setting (Tower Footing) \~: 11.6.16.1.1 All the stub angles for tower legs shall be set accurately to the grade and alignment shown on the drawings. The difference in elevation between identical parts any two stub angles shall not exceed 1/1000 of the horizontal disl30ce
of
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Construction o/Transmission Lines
16 between the stubs,allowance being made for difference, if any, in the lengths of legs and extensions. The actual elevation of any stub angle shall not differ from the computed elevation by more than 1/100 of foundation depth. Stub angles shall be located horizontally so that each is within 6mm of its correct position, and the batter of the stub angles shall not differ from the correct t>1uer by more than either 1/100 of exposed stub length, or by the amount of playas offered by the clearance between bolts and holes of the stub-setting template. To ensure greater accuracy, the hole clearance shall not be greater than 1.5mm o~ the punched side of the Template members. 11.6.16.1.2 If the actual elevation of stubs is beyond 6cm as found after casting the foundation and on the plus side (that is, if the foundation is raised) equivalent depth of earthwork will be provided over the top of the foundation as per design requirements with particular reference to such location. By design requirements is meant the earth required lO resist uplift forces. 11.6.16.1.3 The following tolerances shall be applicable in case of position of foundations erected with reference to the tower positions spotted on Survey Charts: Type oCTower GutoC Aligrunent
From Centre Line of Route
From Transverse Centre line
Suspension
0.5 degree
25mm
±250mm
Tension
05 de!,'fee
25mm
±25mm
(Set at bi-section of deviation angle)
11.6.16.2 Concrete and Form Dimensions The maximum tolerance on the dimensions shall be ±10 mm. AlllOlerances shall not be on the negative side. 11.7 ERECTION OF SUPER STRUCTURE AND FIXING OF TOWER ACCESSORIES The towers shall be erected on the foundations not less than 10 days after concreting or till such time that the concrete has acquired sufficient strength. The towers are erected as per the erection drawings furnished by the manufacturers to facilitate erection. For the convenience of assembling the lOwer parts during erection operations, each member is marked in the factory lO correspond with a number shown in the erection drawing. Any damage to the steel and injuring of galvanising shall be avoided. No member shall be subjected to any undue over stress, during erection. 11.7.1 Method of Erection There are four main methods of erection of steel transmission lOwers which are described as below: (i)
Buil~~up method or Piecemeal method.
(iU
Section method
(iii)
Ground assembly method.
11.7.1.1 Built Up Metlwd This method is most common1y used in this country for the erection of 66 kV, 132 kV, 220 kV and 400 kV transmission line lOwers due to the following advantages: (i) Tower materials can be supplied to site in knocked down condition which facilitates easier and cheaper transportation. (ii) It does not require any heavy machinery such as cranes etc. (iii) Tower erection activity can be done in any kind of terrain and mostly throughout the year. (iv) Availability of workmen at cheap rates. This method consists of erecting the towers, member by member. The lOwer members are kept on ground serially according to erection sequence to avoid search or time loss. The erection progresses from the bottom upwards. The four main comer leg members of the fIrst section of the tower are fIrst erected and guyed off. Sometimes more than one contiguous leg sections of each comer leg are bolted together at the ground and erected. The cross braces of the first section which are already assembled on the ground are raised one by one as a unit and bolted to the aIreadyerected comer leg angles. First section of the tower thus built and horizontal struts (belt members) if any, are bolted in position. For assembling the second section of the tower, two gin poles are placed one each on the top of diagonally opposite comer legs. These two poles are used, for raising parts of second section. The leg members and braces of this section are then hoisted and assembled. The gin poles are then shifted to the comer leg members on the top of second section to raise the parts of third section of the tower in position for assembly. Gin poles are thus moved up as the tower grows. This process is continued till the complete tower is erected. Cross-arm members are assembled on the ground and raised up and fixed to the main body of the lOwer. For heavier towers, a small boom is rigged on one of the tower legs for hoisting purposes. The members/sections are hoisted either manually or by winch machines operated from the ground. For smaller base towers/vertical configuration towers one gin pole is used instead of two gin poles. In order to maintain speed and efficiency,· a small assembly party goes ahead of the main erection gang and its purpose is lO sort out the tower members, keeping the members in correct position on the ground and ,assembling the panels on the ground which can be erected as a complete unit. Sketches indicating different steps or erection by built up method are shown in Annexure-'L' 11.7.1.2 Section Method In the section method, major sections of the tower are assembled on the ground and the same are erected as units.
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is approximately 10 m long and is held in place by means of guys by the side of the tower to be erected. The two opposite sides of the tower section of the tower are assembled on the ground. Each assembled side is then lifted clear of the ground with the gin or derrick and is lowered into position on bolts to stubs or anchor bolts. One side is held in place with props while the other side is being erected. The two opposite sides are then laced together with cross members and diagonals; and the assembled section is lined up, made square to the line. After completing the first section, gin pole is set on the top of the first section. The gin rests on a strut of the tower immediately below the leg joint The gin pole then has to be properly guyed into position. The first face of the second section is raised. To raise the second face of this section i~is necessary to slide the foot of the gin on the strut of the opposite of the tower. After the two opposite faces are raised, the lacing on the other two sides is bolted up. The last lift raises the top of the towers. After the tower top is placed and all side lacings have been bolted up all the guyes are thrown off except one which is used to lower the gin pole. Sometimes whole one face of the tower is assembled on the ground, hoisted and supported in position. The opposite face is similarly assembled and hoisted and then the bracing angles connecting these two faces are fitted. 11 .7.1.3 Ground Assembly Method This method consists of assembling the tower on ground, and erecting it as a complete unit. The complete tower is assembled in a horizontal position on even ground. The tower is assembled along the direction of the line to allow the crQSsarms to be fitted. On slopping ground, however, elaborate packing of the low side is essential before assembly commences. After the assembly is complete the tower is picked up from the ground with the help of a crane and carried to its location. and seton its foundation. For this method of erection, a level piece of ground close to footing is chosen from the tower assembly. This method is not useful when the towers are large and heavy and the foundations are located in arable land where building and erecting complete towers would cause damage to large areas or in hilly terrain where the assembly of complete tower on slopping ground may not be possible and it may be JiiffIcult to get crane into position to raise the complete tower.
yards where these are fabricated and then transported one by one to line locations. Helicopter hovers over the line location while the tower is securely guyed. The ground crew men connect and tighten the tower guys. As soon as the guy wires are adequately tensioned the helicopter disengages and flies to the marshalling yard. This method is adopted where approach is very difficult or to speed up the construction of the transmission line. 11.7.2 Tightening of Nuts and Punching of Threads and Tack Welding of Nuts All nuts shall be tightened properly using correct size spanners. Before tightening it is ensured that filler washers and plates are placed in relevent gaps between members, bolts of proper size and length are inserted and one spring washer is inserted under each nut. In case of step bolts, spring washer shall be placed under the outer nut. The tightening shall be carried on progressively from the top downwards, care being taken that all bolts at every level are tightened simultaneously. It may be better to employ four persons, each covering one leg and the face to his right The threads of bolts shall be projected outside the nuts by one to two threads and shall be punched at three positions on the top inner periphery of the nut and bolt to ensure that the nuts are not lossened in course of time. If during tightening a nut is found to be slipping or running over the bolt threads, the bolt together with the nut shall be changed outright. 11.7.3 Painting of Joints For galvanized towers in coastal or highly polluted areas, the joints shall be painted with zinc paint on all contact surfaces during the course of erection. 11.7.4 Checking the Verticality of Erected Towers The finally erected tower shall be truly vertical after erection and no straining is permitted to bring it in alignment Tolerance limit for vertical shall be one in 360 of the tower height
In India, this method is nOl generally adopted because of prohibitive cost of mobile crane, and non-availability of good approach roads to tower location.
11.8 EARTHING 11.8.1 Each tower shall be earthed after the foundation has been cast. For this purpose, earth strip shall be fixed to the stub during concreting of the chimney and taken out horizontally below the ground level. In normal circumstances, the earth strip shall be provided on No.1 stub leg as given in Figure 3, i.e. the leg with step bolts.
I! .7.1.4J1elicopter Method In the, helicopter method, the transmission tower is erected in sections. For example bottom section is first lifted on to the stubs and then the upper section is lifted and bolted to the first section and the process is repeated till the complete tower is erected. Sometimes a completely assembled tower is raised with the help of helicopter. Helicopters are also used for lifting completely assembled towers with guys from the marshalling
11.8.2 Tower Footing Resistance The tower footi~ resistance of all towers shall be measured in dry v.:eather after tJ:teir erection and before the stringing of earthwire. In no case the tower footing resistance shall exceed 10 ohms. In case the resistance exceeds the specified values, multiple pipe earthing orcounterpois'e earthing , shall be adopted in accordance with the following procedure, but withQut interferring with the foundation concrete even
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Figure 3: Designation of Tower Legs, Footing and Face
1. 2. 3. 4.
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represents leg or pit No.1 represents leg or pit No.2
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represents leg or pit No.3
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represents leg or pit No.4
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A. represents near side (NS) transverse face B. represents near side (NS) longitudinal face C. represents far side (FS) transverse face D. represents far side (FS) longitudinal face NOTE 1: Danger and number plates are localed on face 'A' NOTE 2: Leg 1 represents .the leg with step bolts and anti-climbing device gate, if any.lftwo legs with step bolts are required, the next is No.3 leg.
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though the earth strip/counterpoise lead remains exposed at the tower end The connections in such case shall be made with the existing lattice member holes on the leg just above the chimney top. 11.8.3 Pipe Earth The installation of the pipe earth shall be in accordance with IS : 5613-19'&"1Part II/£ection 2). A typical example of pipe type of earthing is given in Annexure- 'M' 11.8.4 Counterpoise Earth . Counterpoise earth consists of four lengths·of galvanized steel stranded wires, each fitted with a lug for connection to the tower leg at one end. The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 450mm below ground level. The length of each wire is normally limited to 15m but may be increased ifthe resistance requirements are not met. Galvanized steel stranded wire preferably of the same size of the overhead ground wire may be used for this purpose. A typical example of counterpoise type earthing of tower is given in Annexure- 'N'. 11.9 STRINGING OF CONDUCTORS 11.9.1 Mounting of Insulator Strings, and Running Blocks 11.9.1.1 Suspension insulator strings shaIl be used on $USpension towers and tension insulator strings on angle and dead end towers. The strings shall be fixed generally on the tower just prior to the stringing of conductors. Damaged insulators and fittings, shall not be used in the assemblies. Before hoisting: all insulators shall be cleaned in a manner that will not spoil, injure or scratch the surface of the insulator, but in no case shall any oil be used for the purpose. Security clips shall be in position for the insulators before hoisting. Arcing horns or guard rings, if required, shall be placed along the line on suspension, and facing upwards on tension insulator string assemblies.
11.9.1.2 Traveller/Running Block Installation Installation of travellers, including finger lines where used, requires consideration of traveller attachment methods and the need for and location of traveller grounds and uplift rollers. For single conductor venical insulator assemblies, the travellers are normally connected directly to the insulators, and with 'vee' string insulator assemblies, to the yoke plate. For most bundled conductor lines, the travellers are connected to the yoke plate. With post type insulators, the travellers are connected to the end of the insulators. Where travellers are installed to string through tension towers, the travellers are normally connected directly to the tower. If substantial line angles are involved, two travellers in tandem may be requUed to reduce the bending radius of the conductor or the load on each traveller, or both.
Where bundled conductor traveUers are used atline angle locations ~rover 5 degrees, it is advisable to change to individual··single conductor travellers after the passage of the running board to facilitate accurate sagging. When adequate quantities of travellers are available, it is com mon practice to install travellers alongwith the insulators. Under some situations traveUers may be attached to slings or rods in place of the normal insulator assembly. Sketch of travellers is shown in Annexure- '0' ~
Use of travelling grounds and choice oflocations must be based on the degree of exposure to electrical hazards. When such hazards exist, as a minimum, traveUer grounds should be installed at the first and last tower between tensioner and puller. When stringing in proximity to energized lines, additional grounds shall be installed as required, but at a maximum distance not exceeding 3 km. Additionally, grounds shall be instaIled within a reasonable distance on each side of an energized crossing, preferably on the adjacent structure. Travellers with grounds are usually sensitive to direction and care must be exerfLsep in hanging the travellers. Usually the grounds ~~~UllThg end. Each traveller with grounds must be connected with temporary grounding sets to provide an electrical connection between the traveller and earth, or to some conducting medium that is at earth potential. Personnel should never be in series, with a ground lead. Traveller grounds should have a suitable grounding stub located in an ac.cessible position to enable placing and removing the ground clamps, with hot sticks when necessary. Traveller grounds also help protect the sheave linings. At the time the travellers are hung, finger lines, when used, should be installed and tied off at the base of the structures. If the helicopter method of pilot line installation is not to be used, the pilot line could be installed at this time in lieu of finger lines. 11.9.2 Paying out of Earthwire and Conductor
11.9.2.1 Paying out of Earthwire Normally earthwire drums are mounted on a turn table. Pulling machine/tractor are employed to pull the earthwire. Earthwire running blocks are hoisted on the towers prior to taking up of this operation. The earthwire while paying out passes through theearthwirerunning blocks. Earthwiresplices shall be made in such a way that they do not crack or get damaged in the stringing operations. It should be noted that no earthwire joints are·allowed within 30m from the tension or suspension clamp fittings. 11.91.2 Paying out of Conductor 11.9.2.2.1 Slack Layout or Direct Installation Method: Using this method, the conductor is payed out over the ground rollers by means of a pulling vehicle or the ~l carried along the line on a vehicle. The conductor reels are positioned on reel /
I
20 stands or jacks, either placed on the ground or mounted on a transporting vehicle. These stands are designed to support the reel on a shaft permitting it to rotate as the conductor is pulled OUl Usually a braking device is provided to prevent overrunning and backlash. When the conductor is payed out past a tower pulling is stopped and the conductor placed in travellers are attached to the structure before proceeding to the next structure. This method is generally applicable to the construction of new lines in cases where maintenance of conductor surface condition is not critical and where terrain is easily accessible' to a pulling vehicle. The method is not usually economically applicable in urban locations where hazards exist from traffic or where there is danger of contact with energized circuits, nor it is practical in mountainous regions inaccessible to pulling vehicles. Major equipmem required to perform slack stringing includes reel stands, pulling vehicles and a splicing cart.
11.9.2.2.2 Tension Stringing Method Multi-conductor lines shall generatly be strung with the help of tension stringing equipment. Using this method, the conductor is kept under tension during the stringing process. Normally, this method is used to keep the conductor clear of the ground and obstacles which might cause conductor surface damage and clear of energized circuits. It requires pulling of a light pilot line through the travellers, w~i_ch in tum is used to pull in a heavier pulling line. The pulling line is then used to pull in the conductors from the reel stands using specially designed tensioners and pullers. For lighter conductors, a light weight pulling line may be used in place of pilot line to directly pull in the conductor. A helicopter or ground vehicle can be used to pull or layout a pilot line or pulling line. Where a helicopter is used to pull out a line, synthetic rope is normally used to attach the line to the helicopter and prevent the pulling or pilot line from flipping into the rotor blades upon release. The tension method of stringing is applicable where it is desired to keep the conductor off the ground to minimise surface damage or in areas where frequem crossings are encountered. The amount of right of way travel by heavy equipment is also reduced. Usually, this method provides the most economical means of stringing conductor. The helicopter use is particularly advantageous in rugged or poor! yaccessible terrain. Major equipment required for tension stringing includes reel stands, tensioner, puller, reel winder, pilot line winder, splicing cart and helicopter or pulling vehicle. While running out the conductors, care shall be taken such that the conductors do not touch and rub against the ground or objccts which could cause scratches or damage to the strands: The conductor shall not be over-strained during erection. The -- -
Construction a/Transmission Lines
Wherever required jointing of conductor during paying out will be carried out.
11.9.2.2.2.1 Typical Procedures/or Stringing Operations 11.9.2.2.2.1.1
Site Selection, Equipment Location, Anchor and Equipment Grounding
11.9.2.22.1.1.1 Sile Selection
The selection of pull, tension, anchor and splicing sites must consider accessibility, location of deadments, length of conductor to be strung, available conductor and line lengths, puller capacity, including placement of pullers, tensioners and conductor anchor locations, placemem of reel stands, pilot line winders, reel winders and the ability to provide an adequate grounding system. 11.9.2.2.2.1.1.2 Equipmenl LocatiollS
The locations of the puller, tensioners and intermediate anchor sites must be selccted so that the structures are not overloaded. A pulling line slope of three horizontal to one . vertical from the traveller to the site is considered good practice. It is also necessary that the puller be positioned so that the pulling line enters the machine at the smallest horizontal angle thereby minimizing the possibility of damaging the line. When a bull wheel type puller is employed, the reel winder to recover the pulling line is located at the pulling site. The pilot line winder is located at the tensioner site. "The arrangement of the tensioner and reel stands should be such that the lateral angle between the conductor as it approaches the bull wheel and the plane of rotation of the wheel is not large . enough to cause the conductor to rub on the sides of the groove. For example, birdcaging problems were eliminated in large conductors by using a maximum fleet angle of 1.5 degree from the plane normal to. the conductor reel axis and a back tension of approximatel y4500 N. Problems of birdcaging are normally more acute in the case of large conductors having three or more aluminum layers. 11.9.2.2.2.1.1.3 Anchors
Anchors are normally required for holding equipment in place and snubbing conductors against tensions imposed. The type of anchor is dependent upon the soil conditions and stringing and sagging tensions. Portable equipment as well as ground type anchors are often used for this purpose. Slack should be removed from all anchor lines prior to loading to minimize the possibility of equipment movement or impact loads to the anchors. 11.9222.1.1.4 Equipment Grounding
Adequate grounding most be established at all sites. The methods required and equipment used will be deteqnined by the degree of exposure to electrical hazards and the soil conditions at the site. All equipment, conductors, anchors and
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Once the ropepulIing lines have been installed prior to pulling in any conductor or conduct.ivc type p~lIing lines, a running ground must be installed betwccn the reef stand or tcnsioncr for conductor, or puller for pulling line, and the first tower. This ground must be bonded to the ground previously established at the site. Pulling lines are usually pulled in under tension. The pulling line is then connected to a single conductor through swivel link, or to bundle conductors through swivel links and a running board. Swivel links should not be used on a three strand synthetic pulling line. Pulling lines may be synthetic fibre or wire rope. When wire rope is used, it is tecommended that swaged type or braided type be used since it has less tendency to rotate under load, which minimizes spinning problems. A ball bearing swivel link is usually used for the connections betwee~ conductors, pulling lines and running boards. Swivel links must be sufficient rated worked load to withstand loads placed on them during tension stringing. They should also be compatible with the travellers being used so that they can pass through without spreading or damaging the sheaves. These special line stringing swivel links are clevis type and compatible with woven wire grips and swaged steel pulling lines. It is recommended that swivel links not be passed over bullwheels under significant tension since they may be weakened or damaged due to bending. When reeving the bullwhccls of a tensioner with the conductor entering and leaving the wheel from the top facing in the direction of pull, the conductor should enter from the left and leave from the right for right hand lay (standard for aluminium conductor) and enter from the right and leave from the left for left-hand lay (standard for groundwire). The procedureeliminates the tendency of loosening of outer layer strands while conductor passes around the bull wheel. It is recommended that conductor of only one manufacHIrer be used in a given pull, and preferably in any given ruling span. This precaution helps in minimizing the.possibility of difference in sag characteristic of conductor significantly. Attachment of the conductor to the pulling line, running board or to another reel of conductor to be pulled successively is accomplished by the use of woven wire grips. These grips should be compatible strength wise and sized as close as possible for the conductor or pullil\g line on which they are .used. 9verall diameter of the grip over the conductor or rope should be small enough to pass over the sheaves without damage to the sheave or its lining and the grip must also be capable of mating with a proper size swivel link. Metal bands should be installed over the grip to prevent it from accidentally coming off and dropping the conductor. The open end of the grip should be secured with two bands. This should then be wrapped with tape to prevent accidentally
stripping the grip off the conductor if the end were to snag OJ catch. This is particularly important when these grips are used on pulling lines or between lengths of conductor when more than one reel is strung. The grips will then pass through the travellers backwards and if the ends are not banded and taped, they may slip off.
.
Experience has shown th.at pulling speed is an important factor in achieving a smooth stringing operation. Speeds of 34 kmlhour usually provide a smooth passage of the running board or connecting hardware, or both, over the travellers, whereas slower speeds may cauSe significant swinging ofthe traveller and insulator hardware assemblies. Higher speeds . create a potential hazard of greater damage in case of a malfunction. The maximum tension imposed on a conductor during stringing operations should not exceed than necessary to clear obstructions on the ground. This clearance should be con frrrned by observation. In general, stringing tension of about one-half of the sagging tension is a good criterion. If greatertensions are required, consideration must be given to any possible prestressing of conductors that may result, based on the tension and time involved. Consideration must also be given to the fact that when long lengths of conductor are strung, the tension at the pulling end may exceed the tension at the tensioner by a significant amount. Difference in tension is caused by the length of conductor strung, number and performance of travellers, differences in elevation of supporting structures, etc. Light and steady back tension should be maintained on the conductor reels at all times sufficient to prevent over run in case of a sudden stop. It must also be sufficient to cause the conductor to lie snugly in the first groove of the bullwheel and to prevent slack in the conductor between bull wheels. It may be necessary periodically to loosen the brake on the reel stand as the conductor is payed off. As the reel empties, the moment arm available to overcome the brake drag is reduced, and the tension therefore rises. This may cause the conductor to wedge into the underlying layers on the reel. . The reel should be positioned so that it will rotate in the same direction as the bullwheels. looSening of the stranding' that often occurs between the reel and the bull wheels of the tensioner is caused to a great extent by coil memory in the conductor. As the conductor is unwound from the reel and straightens out, the outer strands become loose, a condition that is particularly noticeable in a large diameter conductorandcan be best observed at the point at which it leaves the reel. As the conductor enters the bull wheel groove, the pressure ofcontact tends to push the loose outer strands back towardsrJie reel where the looseness accurg,u!ates, leading to the condition commonly known as birdcaging. If this condition iSoot controlled, the strands can become damaged to the extent Hi'at the damaged area of conductor must be removed. lbls'pr6blem can be remedied by allowing enough distance between the reel and tensioner to permit the strand looseness to distribute along
I 22 _____ . _. __ . the intervening length of conductor and simultaneously main-
taining enough back tcnsion on the reel stretch the core and inner strands to sufficiently tighten the outer strands. The maximum time conductors may safely remain in the travellers depends on wind induced vibration or other motion of the conductors. Wind blown sand can severely damage conductors in a few hours if clearance is less than about 3m over loose sand with little vegetation. Damage from vibration at sagging tensions is quite possible and, when required, dampers should be installed promptly. However, at lower tensions generally used for initial stringing, damage to conductors or sheave bearings, or both, is not likely to occur from vibration. Even for travellers having lined sheaves with root diameters 20 times the conductor diameter, it is important to complete conductor stringing, sagging, plumb marking, c~ip ping, spacing and damping operations as soon as possible to prevent conductor damage from weather, particularly wind. Conductor should not be strung if adverse weather is predicted before the entire sequence can be completed. Sub-conductoroscillation may occur in bundled conductor lines and tie-down methods. Temporary spacers, or other means may be required to prevent conductor surface damage prior to installation of spacers. Temporarily positioning of one sub-conductor above another to prevent conductor clashing is undcsirable since different tension history will produce subconductor mismatch unless the tensions are low and duration short enough so that creep is not a factor. Conductor clashing can mar the strands and produce slivers which can result in radio noise generation. If a bull whccltype puller is utilized, the pulling line must be recovered during the pulling operation on a separate piece of equipment. This function is usually performed by a reel
windcr which is placed behind the puller in an arrangement similar to the reel stand at the tension site. These coils shall be removed carefully and if another length is required to be run out, a joint shall be made according to the recommendation of the manufacturers. Drum battens shall be removed just prior to moving drums on drum stands. Drums will be transported and positioned on station with the least possible amount of rolling. The conductors, joints and clamps shall be erected in such a manner that no birdcaging, over-tensioning ·of individual wires or layers or other deformation or damage to the conductors shall occur. Clamps or hauling devices shall, under erection conditions, allow no relative movement of strands or layers of the conductors. Scaffolding shall be used where roads, rivers, channels, tclecommunication or overhead power lines, railway lines, fences or walls have to be crossed during stringing operations. It shall be seen that nonnal services are not interrupted or damage caused to property. Shut-down shall be obtained when
The sequence of running out shall be from top to downwards i.e. the earthwire shall be run out first, followed by the conductors in succession. In case of horizontal configuration tower, middle conductor shall be strung before stringing of outer conductors is taken-up. A sketch of Tension stringing operation is shown in Annexure-'P'
11.9.3 Repairing of Conductor Repairs to conductors, in the event of damage caused to isolated strands of a conductor during the course of erection, if necessary, shall be carried out during the running out operations, with repair sleeves. Repairing of conductor surface shall be done only in case of minor damage, scuff marks etc., keeping in view both electrical and meChanical safe requirements. Repair sleeves may be used when the damage is limited to the outer layer of the conductor and is equivalent to the severances of not more than one third of the strands of the outer most layer. No repair sleeve shall be fiued within 30m of tension or suspension hardware fittings, nor shall more than one repair sleeve per conductor normally be permitted in any one span. 11.9.4 Jointing The fullest possiblc usc shall be made of the maximum conductor lengths. in order to reduce to a minimum number of joints. All the joints on the conductor shall be of compression type, in accordance with the recommendations of the manufacturers for which all necessary tools and equipments like compressors, die sets etc., shall be arranged. The final conductor surface shall be clean smooth and shall be without any projections, sharp points, cuts, abrasions etc., Conductor ends to be joined shall be coated with an approved grease immediately before final assembly. Surplus grease shall be removed after assembly. All joints or splices shall be made atieast30 metres away from the structures. No joints or splices shall be made in tension spans. No tension joint shall be used in any span crossing other major power lines. The compression type fitting used shall be of self-centering type or care shall be taken to mark the conductors to indicate when the fining is centred properly. During compression or splicing operation the conductor shall be handled in such a manner as to prevent lateral or vertical bearing against the dies. After pressing the joint the aluminium sleeve shall have all corners rounded, burrs and sharp edges removed and smoothened. 11.9.5 Final Sagging of Conductor and Earthwire The final sagging of the conductor shall be done by sagging winches.
After being rough sagged the conductor/earthwire shall
I I
I.
1
, I
J
l 1
IIUllfS
OCIOre DCmg pulled to the specified sag.
The tensioning and sagging shall be done in accordance with the approved stringing chans before the conductors and earthwireare finally attached to the towers through theearthwire clamps for theearthwire and insulatorslrings fortheconductor. The sag will be checked in the first and last span of the Section in case of Sections upto eight spans and in one intermediate span also for sections with more than eight spans. The sag shall also be checked when the conductors have been drawn up and Iran sported from running blocks to the insulator clamps. The running blocks, which are suspended from the transmission Slructure for sagging shall be so adjusted that the conductors on running blocks will be at the same height as the suspension clamp to which it is to be secured. At sharp vertical angles, the sags and tensions shall be checked on both sides of the angle, the conductor and earthwire shall be checked on the running blocks for quality oftension on both sides. The suspension insulator assembly will normally assume vertical positions when the conductor is clamped. Tensioning and sagging operations shall be carried out in normal weather when rapid changes in temperatures are not likely to occur. Sag board and dynamometers shall be employed for meac;uring sag and tension respectively. The dynamometers employed shall be periodically checked and calibrdted with a standard dynamometer. Attempts to sag conductor on excessively windy day should be avoided since serious error can result due toconductor uplift caused by wind pressure on the conductor. Should severe wind conditions occur when sagging is in progress, the sagging must be stopped till peaceful conditions prevail to resume sagging. Once a Section hac; been sagged, the sub-conductors of the bundle should be checked for evenness. Unevenness, if any, shall be rectified as far as possible with the help of sag adjuster.
)
I
\
I ~
)I I
I
1
j
The travellers which are used to string conductor are not frictionless and therefore, can cause problems during a sagging operation. If one or more of the Iravellers becomes jammed, sagging can become very difficult A Iraveller which swings in the direction. of the pull may be an indication of a defective traveller. Should unexplainable sagging difficulties occur, the traveller should be checked. Tensions applied to the conductor to overcome sticky or jammed travellers can eause sudden, abrupt movement of the conductor in the sagging spans and . quickly cause change of sag, particularly, if the conductor is already tensioned to the required value. During sagging care shaJl be taken to eliminate differen-_ tial sags in the sub-conductor ac; far as possible. However, in no case sag mismatch of more than 25mm shall be allowed. 11.9.6 Clipping in/Clamping in of Conductors The clipping portion of the conductor stringing operation
involves thework foil owing sagging and plumb marking of the conductors. This entails removing the conductors from the travellers and placing them in their permanent suspension clamps attached to the insulator assemblies. When clipping is being done, care must be exercised to ascertain that the conductors are grounded prior to clipping despite the fact that the lines being clipped are not attached to any electrical source. This involves placing a locaJ ground upon the conductor at the location of work. After the conductors have been marked, the erection crew will lift the weight of the conductors, allowing the travellers to be removed and the suspension clamps, and armour rod, if any used, to be placed on the conductors. Lifting is nonnally done by use of a hoist suspended from the structure and a conductor lifting hook which is designed so as not to notch or severely bend the conductors. After placing the suspension clamps on the conductor, the hooks are lowered thereby placing the weight of the conductor on the suspension clamp and completing the assembly. Where bundle conductors are used, the multiple conductors may be lifted simultaneously by using a yoke arrangement supporting the hooks and a single hoist or other lifting means. 11.9.7 Installation of Spacers Following the clipping operations for bundled conductor lines, spacers must be installed. This is done by placing the erection crew on the conductors in the 'conductor car' normally known as spacer cycle to ride from structure. Depending on the length of line Lo be spacered and the equipment available, cars may be hand powered, towed by persons on the ground or in adjacent slrucLures wiLh ropes, or powered by a small engine on the car itself. Care must be exercised to ensure thaL the concentrated load of the man, car and equipment does not increase the sag appreciably to cause a hazard from obSlructions over which the car will pass. The installation of the spacers on the conductor varies with the type and manufacture of the spacer and is normally done in accordance with the manufacturer's recommendations. The load of the man, car and equipment should be equally diSlributed to all sub-conductors of the phase. This is particularlyimportant at the time each spacer is attached. Number of spacers. per span and the spacings are provided as per the approved spacer placement chart 11.9.8
Installation of Vibration Dampers/Spacer Dampers Vibration Dampers/Spacer Dampers are nonnally placed on the conductors immediately following clipping to prevent any possible wind vibration damage to the conductors which at critical tensions and wind conditions can occur in a matter of a few hours. The number of dampers/spacer dampers and spacing are provided as per the design requirement and instructions of the manufacturers.
24
Construction of Transmission Lines
11.9.9 Jumpering The jumpers at the Section and angle towers shall be fonned to parabolic shape to ensure maximum clearance requirements. Pilot suspension insulator string shall be used, if found necessary, to restrict the jumper swings to the design values. Clearance between the conductors and ground and between jumpers and the tower steel work shall be checked during erection and before handing over the line. 11.9.10 Ground Undulation The provision of 150mm shall be made to account for any undulations in the ground in final still air sag at maximum. 11.10
HOT-LINE STRINGING OF E.H.V. LINES
11.10.1 General Hot line stringing means stringing of second circuit on the same tower with first circuit electrically & mechanically loaded. This is shown in Figure A. 11.10.1.1 With the available techniques, the hot-line stringing is done in this country only upto 220 kY. The advantage of stringing second circuit at a later'date (with hot-line method) is saving in initial capital investment in the form of conductors, insulated hardware. Besides, with provision of Double circuit towers from the beginning saves way problems as second corridor is not required for second circuit 11.10.2 Precautions 11.10.2.1 Hot-line stringing is a specialised job and calls for special precautions. All the crew members are provided with rubber shoes and hand-gloves and are compelled to use them during the stringing. 11.1 0.2.2. All the drums of conductor and pilot wires are solidly earthed. All the tension locations, where the conductor ends are terminated, are solidly earthed. 11.10.2.3 In addition to above, during final sagging and clipping operation, standard earthing rods are used for con, necting each conductor to the tower body.
Circuit No-1 strung and energised
11.10.3 Operations 11.10.3.1 Arrangement for earthing the conductor drums and pilot wire drums is made at both the ends of the section under stringing. The hoisting of insulators, clamping of pilot wire and the conductor and rough sagging of conductor is done as per nonnal stringing method. 11.10.3.2 Before marking and clipping the dead ends, each phase conductor is solidly earthed in two separate sets. One set is earthed by means,of droppers and earthing rods and second set is by earthing of conductor end to tower body. This is shown in the Figure B. While removing the second set of earthing, the conductor end is removed first and the tower end later. Similarly in case of the first set the cable is disconnected from canductor end first and the rod end later. 11.10.3.3 Similarly, before clipping the canductor on the suspension towers, each canductor on both the sides of the clamp is earthed to tower body. After the clipping is aver, the earthing cable is first removed from the conductor end and later from the tower end. This is shown in the Figure C. 11.10.3.4 In arder to limit the parallelism and induced voltages, it is advisable to do thejumpcring work at the end. While daing the jumpering work also the earthing cables are required to' be pravided.
11.10.4 Earthing 11.10.4.1 Solid earthings are provided by driving one or mare G.I. SPIKES in the soil as dane in pipe type of earthing. If required, more pipes are driven at the same place. In any case the soil resistance should not be more than 5 ohms. 11.10.4.2 In case of rocky soils, counterpoise type earthing system is used. The length of the wires is decided by trial & error till the earth resistance is lowered to 5 ohms or less. 11.10.4.3 For earthing a t1exible copper cable having 10 sq. mm area (20 Ampere capacity) is used. The cable is generally armoured type for rough use. Proper clamps/connectors are used to connect the cable to the conductor and to the earth.
Circuit No.-2 to be strung as hot line
, I
~ 1 1
!
I I
I
,
(
E/W
TIC
First set
H/(
B/C
2 10 mm flexible copper cable Tension tower Standard earthing rods
G.l.
Earth
Longitudinal View FIGUREn E/W
TIC
Suspension insulator string 10 mm 2 flexible earthing cable
H/C
B/C
Suspension tower
FIGUREC
26.
. - - - - - - - - - - - - . ------------- -- - - _ .... _. . . -
11.11 PROTECTION OF TOWER FOOTINGS The woi"k includes all necessary stone reveunem, concreting and earth filling above ground level and the clearance from )tacking on the side of all surplus excavated soil, special measures for protection of foundations close to or in nallahas, river beds, etc., by providing suitable reveunenl or galvanised wire nelling and meshing packed with boulders. A typical revetment drawing is shown in Annexure- 'Q' 11.12
TESTING AND COMMISSIONING
11.12.1 General Before the line is energised, visual examination of the line shall be carried out to check that all nuts and bolts are tight and insulators and accessories ar9 in position. The earth connections shall also be checked to venfy that these are in order. 11.12.2 Testing Before commissioning of the lines, the following tests may be carried out:
(a) Conductor continuity test-The objective of this test is to verify that each conductor of the overhead line is properly connected electrically (that is, the value of its electrical resistance docs not vary, abnormally from that of a continuous conductor of the same size and length). The electrical resistance of the conductor shall be measured with a Wheatstone bridge or other suitable instrument. (b) Insulation resistance test-This test may be carried out with the help of a 5 kV megger preferably driven to ascertain the insulation condition of the line. 11.12.2.1 The line may then be kept charged on no load at the power frequency voltage preferably for 72 hours. for the purpose of full scale testing. 11.12.3 Statutory Requirements
The statutory authorities shall be informed before commissioning the lines and their approval obtained in accordance with Indian Electricity Act, 1910 and Indian Electricity Rules, 1956. (For details see Rules 63 to 69 of Indian Electricity Rules, 1956). 11.13 REFERENCES 1. IEEE Guide to the Installation of Overhead Transmission Line Conductors. (lEE Std. 524-1980). Published by the Institute of Electrical and Electronics Engineers, Inc. 345 East 47th Street, New York 1.0017, Dec' 18,1980. .
Construction a/Transmission Lines
2. The following papers published by the Association of Indian Engineering Industry Transmission Line Division Published on the occasion of International Conference on Trends in Transmission Line Technology during 17th18th April, 1985. (i) "Latest Erection Techniques for Tranmission Line Construction" by Shri R. K. Madan, MIs National Hydro-electric Power Corporation .. (ii) "Tower Foundation design practice" by Shri S.D. Dand, MIs KEC International Limited, Kurla. 3. Overhead Line Practice-by John Mc-COMBE. 4. Manual ofTransmission Line Towers-Technical Report No.9 of Central Board of Irrigation and Power. 5. Text book on "Surveying and Levelling-by Shri T.P. KaneLkar. 6. "Company Standard Guide for Transmission Line Surveying"-EMC Ltd., Calcutta. 7. Indian Standard Codes (a) IS: 5613 (Part II/Section I)-1976-Code of Practice for Design, Installation and Maintenance of Overhead Power Lines-(Lines above 11 kV and upto and including 220 kV). (b) IS: 5613 (Part II/Section 2)-1976-Code of Practice for Design, Installation and Maintenance of Overhead Power Lines-(Lines above 11 kV and upto and including 220 kV). (c) IS : 4091-1979-Code of Pmctice for Design and Construction of Foundations for Transmission Line Towers and Poles. (d) IS: 456-1978-Code of Practice for Plain and Reinforced Concrete. (e) IS: 3043-1966-Code of Pmctice for Earthing. (f) Draft "Indian Standard Code of Practice for Design,
Installation and Maintenance for Overhead Power Lines" -Part 3 (400 kV Lines)-Section I-Design-"IS : 5613 (Part III/Sec. 1.)".
ANNEXURE 'A'
CLEARANCES
1. 1.1
The minimum clearances shall be in accordance with Indian Electricity Rules, 1956 and are given in Table I TABLE·I Minimum Clearances
VOLTAGE CATEGORY (IE RULES, 1956) Nominal System-Voltage Clearance
HIGH VOLTAGE 33kV
66kV
1l0kV 220kV 132kV (Minimum value in m)
(i) Clearance to Ground (a) Across street 6.1 6.1 6.1 (b) Along street 5.8 6.1 6.1 (c) Olher areas 5.2 6.1 S.5 (ii) Clearance to Buildings (a) Vertical (*) -from 3.66 highest ,object 3.97 4.58 (b) Horizontal (+) -from nearest point 2.14 2.75 1.83 (iii) At Crossings with (a) Tramway/trolley bus 3.05 3.36 3.76 (b) Telecom lines 2.44 2.75 (c) Railway # 1 Category 'A' and 'C' Groad Guage Inside station area 10.6 10.0 10.3 Oul<;idc SL.1lion area 7.6 8.2 7.9 Metre/Narrow Gauge Inside station area 9.1 9.5 8.8 7.0 Outside stalion area 6.4 6.7 2. Category 'B'-All Gauges Inside staLion area 12.3 13.7 13.0 11.0 11.7 Outside stalion area 10.5 (iv) Between Lines when crossing each other (derived) 2.44 2.75 2S0V 2.44 2.44 2.44 2.7S 6S0V 11 kV 2.44 2.44 2.75 2.44 2.7S 22kV 2.44 2.44 2.75 2.44 33 kV 2.44 2.75 2.44 66kV 2.75 110kV 2.75 2.75 3.0S 132kV 3.0S 3.0S 4.58 220kV 4.58 4.S8 6.10 6.10 400kV 6.10 10.80 10.80 10.80 ± SOO kVDC 800kV 10.00 10.00 10.00 NOTE 1:
EXTRA HIGH VOLTAGE
$ Should not cross on/near buildings
± 500kV
400kV
800kV
HVDC
6.1 6.1 6.1
7.0 7.0 7.0
8.84 8.84 8.84
13.20 13.20 13.20
12.40 12.40 12.40
4.S8
5.4~$
7.32
11.59
10.90
2.75
3.66
5.49
10.98
9.15
3.97 2.75
4.78 3.05
6.44 4.67
10.9 8.5
11.2 8.8
16.630 14.630
9.8 7.3
10.0 7.6
14.0 12.0
IS.3 13.3
18.63 16.63
3.0S 3.0S 3.05 3.05 3.0S 3.0S 3.05 3.0S 4.S8 6.10 10.80 10.00
4.58 4.S8 4.58 4.58 4.58 4.58 4.58 4.58 4.58 6.10 10.80 10.00
6.10 6.10 6.10 6.10 6.10 6.10 6.10 6.10 6.10 6.10 10.80 10.00
10.14 8.18
10.80 10.80 10.80 10.80 10.80 10.80 10.80 10.80 10.80 10.80 10.80 10.00
10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.80 10.00
_____fo..n~lrUClion of Transmission Lifl!s
2L NOTE 2
For all crossings, the clearance to be obtained at the worst conditions of proximity of wires.
NOTE 3
The above table has been compiled wiLh the help of Indian Electricity Rules 1956
i(a)
Vertical clearance LO be obtained at max!mum still air final sags (at maximum temperature or ice-loaded conductor
(*)
at 0 degree Celcius). ii(b) (+)
Horizontal clearance to be obtained at worst load condition wiLh maximum deflected conducLOr position, including that of insulaLOr string, if any.
iii(c) #
I
Category' A'
tI'dcks elecLrified on 1 500 V dc system.
Category 'B'
tmcks already electrified.or likely to be convertedLO or electrified on 25 kV ac system within the foreseeable future.
Category 'C'
tracks not likely to be electrified in Lhe foreseeable future.
[For categories' A' and 'B' crossings up to 650 V shall be by means of underground (U.G.) cables; while it is recommended that U.G. cable be upto 11 kV. For category 'C', it is recommended that U.G. cable be used UpLO 650 V. Above these, U.G.cable or overhead crossings may be adopted as preferred by the owner. The minimum clearance between any of the owner's conductors or guard wires and the Railway's conducLOrs shall not be less than 2 m.] Station Area means all tracks lying in Lhe area between the outer most signals of a railway station. 1.2 Mid-span clearance between Earthwire and Power Conductor-The following values may be considered subject to Lhe conditions given below: (a)
These should also meet the requirements of angle of shielding.
(b)
The earthwire sag shall be not more than 90 percent of Lhe corresponding sag of power conductor under s1ill air condition for the entire specified temperature range. Line Voltage (kY)
Minimum Mid-span clearance (m)
33
l.5
66
3.0
110
4.5
132
6.l
220
8.5
400
9.0
±500 kYHYDC 800 kY
I
9.0 12.0
Note: The mid-span clcarance shall be reckoned as direct distance between earthwire and top power conductor, in case of vertical or triangular formation of conductors, or outer power conductors, in case of horizontal formation of conductors at minimum temperature and still air conditions. 1.3 Live Metal Clearance : The live metal clearance depends upon Lhe voltage of the conduCLOrs in different operating conditions. The values of these clearances corresponding LO conditions normally considered for the design of lines are given in Table 2 .
ANNEXURE 'A (Contd. TABLE 2 Minimum Electrical Clearances from Live Conductor to Earthed Metal Parts TYPE OF INSULATOR
SWING IN
STRING
DEGREE 2
MINIMUM ELECTRICAL CLEARANCE FOR LINE VOLTAGE 33 kV
66kV
3
4 mm
mm
mm
mm
mm
mm
3050
3750
*
mm (i)
Pin insulator
(ii)
Tension string (Single/Double)
(iii)
(iv)
Jumper
110 kV
5
132 kV
6
220 kV
400 kV
500 kV
8
7
9
Nil
330
Nil
330
915
1220
1530
2130
Nil!
330 330
915
1220
1530
2130
*
915
1220
1530
2130
3050
330
610
915
1070
1675
* *
*
10°
*
330
610
915
1070
330
915
1220
1530
2130
3050
3750
330
915
1220
1530
1980
*
*
330
760
1070
1370
1830
610
915
1220
1675
* *
*
330 330
610
915
1070
*
*
*
330
915
1220
1530
2130
Single suspension string
(v)
*
Double Suspens\on String
Nil
* Not applicable
Note:
The effect of galloping or dencing of conductors has not been taken into consideration while specifying the minimum electrical clearances. 1.3.1 The values given in Table 2 are considered to be suitable for elevations upto 1000 m above the mean see level (MSL). For heights over 1000 m and up to 3000m above MSL, it is recommended that the values should be increased by 1.25 percent for every 100m height or part thereor. SPECIAL NOTE: 1) Value for the 33 kV to 220 kV have been copied from IS 5613 (part II/Sec 1)-1976 2) Values for 400 kV may be checked by the design department 3) Values for 500 kV are to be filled up by the design department.
* To be filled up by Kurla
30
ANNEXURE 'B' Caiculalions of Reduced levels & Chainages A. By Dumpy Level & Chainages Sample field book observations Angle of
Stalion No.
Chainage
Level Readings
0
B
12 17 27 37 50 85 100 150 200 300
Route Plan
line deviation Back
Inter
Fore (ll.l. )
sight
sight
sight
5.62 A
Coli imatioll
Reduced Level L
1~l)6.12
10015'
20°10'
IXX9.17 IX91.64 l~n.X8
0.68
-
R
1X90.50
6.95 4.4X 3.24 2.91 3.25 4.X2 2.94 2.01 1.28 5.44
C
J
1X93.21 IX92.X7 1X91JO 1893.18 UN4.11 1894.84 1895.44 1897.30 1896.64
1900.88
3.58
- 4.24 NOTE: Alllhe values are in meLres B. By Tacheomelric Survey Sample field book Stalion
Angle
Readings
Number
Horizontal
Vcnical
Stadia
Wire
Readings
Top
Mid
Botlom
(n
(M)
(8)
H.I.
(in melrcs) (8)
9 8
7 6 5 4 3 2 1 (x)
10030'(L)
4°10' 8°24' 10°36' 2°18' 0°00' 0°00' (-) 11°05' (- ) 6°10' 2°40' 5°18' 2°12'
3.60 1.50 1.40 1.10
3.04 3.05 2.10 1.15 1.20 1.20
3.00 1.00 1.00 1.00 1.52 3.00 3.00 2.00 1.00 1.00 1.00
2.40 0.50 0.60 0.90
1.4
I.P.
2.96 2.95 1.90 0.85 0.80 0.80
Routs
Plan
L
R
Details
~
ANNEXURE'B' Contd)
Calculations (Tacheometric Survey)
1 1
Stn. No.
(B) 9 6 7 6 8 4
Vertical angle
4°10' 8°24' 10036' 2°18' 0000' 0°00' (-) 1005'
3 (-) 6°10' 2°40' 2 5°18' Ix 2°12' 1 (A) 0000'
Height of Instrument = H.I. = 1.40 m 100.00 R.L. of Instrument Station (R.L~ = Horizontal Vertical m s (T-B) distance V=DTan e D=sxKCos8 1.20 1.00 0.80 0.20 0.00 0.08 0.10 0.20 0.30 0.40 0.40 0.50
R.L..' .. =
RLo~.I±V-m in m
3.00 1.00 1.00 1.00 1.52 3.00 3.00
119.37 97.87 77.29 19.97 0.00 0.00 10.00
0.80 0.00 0.00 (-) 0.19
107.10 114.85 114.86 101.20 99.88 98.40 98.21
2.00 1.00 1.00 1.00 1.00
19.76 29.94
(-) 2.14 1.39
97.26 101.79
39.66 39.94 50.00
3.68 1.53 0.00
104.08 101.93 100.40
8.70 14.45 14.46
Remarks
Angle pt (B)
Exst. pt
CST (1)
Angle pt (A) B.M.l00.00 Where 'K' is the.Instrument Coefficient which is furnished by the Instrument manufacturers. In the above calculations valu of 'K' has been taken as 100. V =DTANe D =sxkxCos28 RLA = RLo+
HI±v-m
Where RLo = Reduced Level of Instrument Station RLA = Reduced Level of Staff Station
Staff
. Collimation tine
~~~----------------D----------------~ G.l.
Stadia with Line of Collimation Inclined
~
N
ANNEXUREC
Typical Sketch of Profile
113
112
(Tower No.'
A
A
/ (Angle point,_Y1
350 420
115 400
400
A
Datum 4000
...'"..
Reduced level Distance in metres
I
co
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-
AP t , 22° 15
co
,., ,., '"
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co
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co co &Ii
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co GO
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oulders
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-------------
ANNEXURE.
Typical Sa g Template Drawing
Ground clearance curve (3) Tower footing curve
(4)
Normal span 400 m
Scale Hor. 1 cm = 20 m Ver. 1 cm = 2 m
PARTICULAR 1. CONDUCTOR MOOSE ACSR 2. ULTIMATE STRENGTH 16434 Kg 3. TEMPERATURE RANGE 00-370-750 4. NORMAL SPAN 400 m 5. SAG OF CONDUCTOR AT MINIMUM TEMPERATURE AT NORMAL TEMPERATURE NOWIND . 6. MAXIMUM SAG CONDUCTOR 12.865 m EARTHWIRE 10.196 m 7. TENS'ION AT MAXIMUM TEMPERATURE STILL WIND 8. TENSION AT MINIMUM TEMPERATURE STILL WIND GROUND CLEARANCE 8.840 m GROUND UNDULATIONS 0.150 m
Construction o/Transmission Lines
34
ANNEXURE·E STRUCTURE LIMITATION CHART/TOWER SPOTTING DATA (FOR 400 KV TRANSMISSION LINES)
Tower Type Max. Angle of Deviation Vertical Load Limitations on Weight Span. Groundwire effect (a) Both Spans (b) One Span Conductor effect (a) Both Spans (b) One Span Weights Groundwire effect (a) Both Spans (b) One Span Conductor effect (a) Both Spans (b) One Span Permissible sum of adjacent span for various deviation angles.
'C' MKD. 'c'
'D'MKD. 'D'
15°
15° to 300
6OO/O.E.
Max. (Min.)
Max. (Min)
.Max. (Min.)
Max (Min.)
600 (200) 360 (100)
600 (0) 360 (-200)
600 (0) 300 (-200)
600 (0) 360 (-300)
600 (200) 360 (100)
600 (0) 360 (-200)
600-(0) 360 (-200)
600 (0) 360 (-300)
350 (117) 210 (58)
350 (0) 210 (-117)
350 (0) 210 (-117)
350 (0) 210 (-175)
2405 (802) 1443 (401)
2405 (0) 1443 (-802) 15°-800 14-876 13-956 12-1034 11-1112 10-1190
2405 (0) 1443 (-802) 30°-800 29-874 28-952 27-1028 26-11()4
2405 (0) 1443 (-802)
'A'MKD. 'A'
'B'MKD. 'B'
2°
2°-80'0 1-838 0-878
60°-800 59-868 58-936 57-1004 56-1074 55-1144
25-1182
Design (a) Groundwire
6.
(i) 32° Full wind
1574
1561/1574
1520/1574
(ii) 00 x 2(3 Full wind
1525
1521/1525
1473/1525
1363/1574 1321/1525
4470
8864/8940 9086/9164
8635/8940 8852/9164
7742/8940 7936/9164
(b) Conductor (i) 32° Full wind (ii) 00 x 2(3 Full wind TOWER TYPE 18m and 25m Extension for Towertype 'A' marked 'A'
4582
(a) Maximum Wind span 300m (b) Deviation Angle odegree (c) Vertical load Limitation on Weight span of Conductor/Groundwire: Minimum Maximum (i) Both spans
600
200
(ii)
~I\l)
1()()
Onf> I1.mm
ANNEXURE I • (Contd, 6A.
18m and 25m Extension for Tower type 'D' marked 'D'
400m 40 degree (c) Vertical load limitation on weight span of Con ductorlGround wire: Minimum Maximum
(a) Maximum wind span (b) Deviation Angle
(i) Both spans
\ 7. 8.
(-) 600
(ii) One span (-) 360 Way leave clearance 26 metres either side from centre of line of tower. Electrical clearance for Railway crossing 17.9m,
o (-) 300
------ -
9.
Minimum clearance between power line to power line crossing
5.490ml
NOTES:
Vertical loads on individual spans are acting downwards for suspension towers. 2. Broken wire condition: As per specification requirement. 1.
3.
4. 5.
6.
7. 8.
Maximum sum of adjacent spans for various angles of deviations are subjected to the condition that maximum live metal clearance and minimum ground clearance are available. Limit of Highway crossing span: 250 metres Maximum deviation angle for dead end tower: (a) Line side and Slack span side: 15 degree on either side. (b) For River crossing Anchoring with longer wind span with 0 degree deviation on crossing span and 30 degree deviation on either side. Angle tower types 'B', 'C' & 'D' are designed for following unbalanced tension resulting from unequal Ruling spans of 200 m and 400 m on each side of the towers for nonnal condition only. Temperatures Unbalanced Tension Groundwire Conductor At 32 degree Celsius (Without wind) 80 983 At Zero degree Celsius (Without wind) 85 376 Tower type 'C' to be u'sed as Transposition tower with 0 degree deviation. Tower type' B' to be used as Section towers. The number of consecutive spans between two section points shall not exceed 15.
\~ ANNEXUREF TOWER SCHEDULE NAME OF THE LINE: Tower No. Final mst.
)/4
Length Span (m)
of Section (m)
05
XX
XX
Angle of
XX
XX
XX
XX
Wt. Span (m)
Type
deviation
of T.ower
L
13°32' OO"L T
B+9
107
R
260
XX
XX
Type
Total
367
of Fdn.
FS
Details of Earthing Type Resistance{ohm} Type IniFinal (P/CP) tial Pipe
5
2
450 )/5
11 kY crossing
06
A
190
190
380
WEe
Pipe
3
2
A
190
189
379
Wet
Pipe
4
2
380 ./6
Nala crossing
07 395
';7
Remarks
2 Nalas crossing
08
A+3
206
217
423
WBe
Pipe
3
2
A
198
194
392
Dry
Pipe
5
3
B
196
196
392
WBe
Pipe
5
3
415
1/8
09 390
/9
2030 10010'30"RT
10 390
~
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ANNEXUREG
Types & Shapes of Foundations Chapter on Construction Activities of EHV Transmission Lines CL. G.L.
LL.
G.L.
CL. _ __ t
._.
V£.I
i _,
G.L.
_,
CL. G.L.
t
_
- - - G.L., CL. - lAW< - -r ,.., VJ - ,_
Pad Fig. 1 Chimney. Pyramid & pad type 0(( foundation for normal dry .oil
Anchor Fig. 2 Block type P.e.e. foundation for soft & hard rock
Fig. 3 Under cut type P.e.e./R.C.e. foundation for soft rock & normal soli
Fig. 4 Spread footing type champhered R.Le. foundations for submerged soils
Fig. 5 Spread footing type chamhered step type R.LC foundations for submerged soils
Fig. , Anchor rod type P.e.e. foundation for hard rock
tt1 ~
Pile cap
1m" G.l.
Fig. 7 er type/under ream ! foundation for c1ayee
--
Fig. 8 Steel plate type . foundation for normal soil·
Fig. 9 Grillage type foundafons for normal cohesive soil.
Fig. 10 Well type foundation for submerged & sandy soils (R.C.C.J
Fig. 11 Special pile type R.C.C. foundation in flowing river
38
Conslruclion of Tra.nsmission Lines
----
ANNEXUREH
Sketch of Hill Side Extensions
tl.
ANNEXURE I
EXCAVA TlON MARKING CHART
_______ --------=1=-=---- -----
ELEVATION
D'I.--4--.
1ft
/
.
/'<
- - - - - - M -------..,.\ PLAN
Dimensions in mm Description
(Normal) wet location
Dimensions for pit marking H
F
M
N
AB
3000
2295
9686
13698
5991
3000
2295
10661
15077
6478
3000
2295
11637
16457
6966
Wet location
Wet location
ABC
ABCD
ABCDE
ABCDEA
. 9686
11981
15227
20453
10661
12956
16202
22118
11637
13932
17177
23783
.
40
ANNEXURE:]
PROCEDURE FOR SETTING STUBS AT SITE BY COMBINED TEMPLATE The Stubs are set with the help of the Stub-setting Templates, which are supplied loose, ready to be assembled at site. All four excavated pits are to be lean concreted to correct level sighted through level and the stubs are to be placed on the lean concrete pad. Correct alignment is carried out by 0.9 kg Plumb bob 4 in numbers hung from centre of horizontal bracings.
Following is the procedure for Stub-setting at site: 1 Assemble the Template as per the drawing alongwith .the supply. 2 Set the Template as per the drawing at site. 3 Place the Stub-setting lacks below the Template. 4 Align Template, alongwith the line and centre it over the centre peg of the location. 5 Fix up the stub to the Template and with the help of a
6
dumpy level, level the Template comers to the required level. Ensure that all the four stubs are at the same level.
7
Check the alignment and centring of the Template again.
8
By placing on 8 to 12 screw jacks according to the length of Template. with a levelling instrument fine adjustment can be made by lifting/lowering the screw jacks, and the stubs can be perfectly levelled. This ensures accurate verticality of the tower. For ensuring all towers in one line and cross-arms at right angle to it, 4 plumb bobs should be dropped from the centre of the horizontal members of the Template to correspond to the cross pegs and alignment pegs given during the line alignment survey for the tower location.
PIT
TEMPLATE SCREWJ
STue
ANNEXUREK
Foundation layout of Unequal leg Extensions
R.L.100m R.L.97m
/
3
/
Om leg extension ''\',\
/
'\
/ / / /
2 3m leg extension
/
/
X R.L.
·0 .
"-
100m
., ,
"-
"-
R.L.98m
"
4
Individual Leg Template
2m leg extension
4m leg extension
---=~--T1
"
T
"
"
"
2m
"" "
II
" " " I,
Pit No.4
Pit No.1
42
Construction o/Transmission Lines ANNEXURE L
Different Steps of Tower Erection
3/4" Polypropylene Rope ""!!::~~_ _ _ _ _~~~
1" Polypropylene Rope
Step No. I
I I
I I
I ~
f!!.-_____~~-=- 1" polypropylene Rope
-4-___
Different Steps of Tower Erection
Step No.
m
""--- 1" Polypropylene Rope
-----+------------~---Step No. IV
44
Construction o/Transmission Lines -----------------------------_ .. _._._---Different Steps of Tower Erection
3/4" Polypropylene rope
Step No. V
Different Steps of Tower Erection
Different Steps of Tower Eredion
GI
a. o
...
GI
c: QI
>. a.
...a.o
:>..
"0 a..
'" Polypropylene rope
Step No. VII
46
-------------------------
Construction o/Transmission Lines -,----_ ..
Different Steps of Tower Erection
,
Step No.VIII
\
Different Steps of Tower Erection
r'U-_ _
1" Polypropylene rope
Step No. IX
\
I
48
Construction o/Transmission Lines _--------
---------------------
......
Typical Sketch of pipe Type Earthing
ANNEXURE M
n.s mm ilia holes for counter poise earthing device
50x6 mm thi,~ G~lvd. steel f1~t extended SOO mm beyono rile concrete Requirement of coke and salt
17.5 mm dia holes for connecting earthing strip I1KD-A - -_ _ _ _I!I!
Coke = ISO kg
..
Salt = 15 kg
'iii
I '.:
I
~.
...
' OJ
Q.
'Q. V1
J:
...'.. .,
..
)(
o
,
"
"
Q. Q.
-0OJ
_,.
.l:
i: :-
:i ~ :t E'" E E
1:
E
~o~
"'-- salt
Detail at-A
(oke &
13.5 mm dia holes for 12 mm dia bolts Pipe flattend & drilled for 12 mm dia bolts
... o
-=. ."
t
C
III III
OJ .0
Detail at-H
o
I-
Detail at-B Material ReQd. Per Earthing Set Bend line Ilty
Desuiption 2S mill di.. bore pipe ho t
dip Gillvd. SOx6 mm thick Gillvd. steel flat-B -2
60x6 RIll thick earthing strip 'A' Reqd one per tower with stub Ilhis strip to be supplied for all tower) This flat will be at right angle to stub & will beco/lle horizontal after twist
2
liillvd. HRH 16 mm dia bolts & nuts with Std. threads (ialvd. HRH 12 mm dia bolts & nuts fully threaded
length in mm 3000 3325
35 30
ANNEXURE N Typical Skech of Counter Poise' Type Earthing Ll. of lower
I \
I \
10weliegS
·_·t·_·
I \. \ \ Reqd length of counter poise wire to minimum of 15.0 m length per leg
Sleeve to be compressed after fixing wire
20 !1!1
!1
rJO.97 mm dia wire
m .,;.......I~:I~I-/ _
TL r
i
r------II
L ____ -- ~
i
85
!3
tTon
~.-ciC>I 1-
t-+
\ C,2 mm dia hole
•
so
COrlStruction of Transmission Lines
ANNEXURE 0
Sketch of Travellers/Running Blocks tAli dimensions are in mml
co
,.,
U'\
Traveller for Single Conductor
.t-:-:-:-:!=_:::!-;;,;;-~~~~ . ~ .....-----'-200
---.,.j
ANNEXURE P
Tension S t~inging Operation
line winder
Transmission Tower Typical equipme~t set up for tension stringing . a two bundle transmission line using bullwheel puller Take up reel stand
Take up reel stand
........ -
·'-·"W'b--·'~_-=h'v",·'_''''''''~~_~''.~:,:~~._· ..
...
Ul
N
Typical Sketch Showing the (ross Section of Revetment for Transmission Line Foundation
ANNEXURE .0
rll .
, h
,, '\ ,,
G.L.
600
stone 7S mm to 1S0mm
M 150 1:2:4 normal mix
e
"
.\Veep holes 100+100
\ I,
I Hand p.ackel/ I stone
'\ "
, \,
1600+450
~,I
I
I "
I
\I· ""
I I' I ,I I ,I
,
, ",I I I' , II
.tj
I I
I LL
e
o
vi ><
IV
:l:
'
0"
",
-0
/ Stone ,I 75mm to
r9i
.5 ~
,.,
::I:
150mm
oII
I!/ .
.c:
I
~~I.
I
::I:
o
"0
8=600 x H/3.846 • ,1~9 8=600+ H tan e
For H:! 1000 d = 230 For H < 1000 d = 150
Stone masonry 1:5 cement mortar =30°-45° depending on the site condition
e
~
c::::;
Notesi-
.;:::
10
1. All dimensions are in mm unless otherwise specified 2. 3. 4. 5. 6. 7. 8. 9.
§.
Weep holes should be of size 100mm)C 100mm or 150mm)C 150mm in case of large size revetment Weep holes should be at 2.sm centres horizontal Centre of top most weep holes to be not less than 300mm below top The minimum depth of revetment wall below G.L. will be 600mm Dimensions of 8 are vaUd only for H not exeeding 5.00m Size of stone for masonry work 300)C 150 x150 and below The masonry work should be carried out in 1:5 cement mortar Size of stone packing at weep hole 75mm to 150mm
...•.... t,·",·~,·~. ~>. ~~
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,
APPENDIX :A
MODERN METHODS OF SURVEYING (Reference to the clause: 11.5.2) 1.1 Satellite Doppler Technique Accurate and flexible survey data are necessary to achieve the minimum cost transmission line routing with the minimum environmental impact. Precise and reliable topographic data arc obtained including detailed and accurate horizontal and vertical terrain information by compiling large scale ''Orthophoto'. maps of the proposed transmission corridors. These give a 'Picture' of the route which is geometrically correct and overlayed on this are contour lines which depictthe changes in elevation of the land. By studying these maps,tmnsmission corridors are selected which are most attractive for tower installation purposes. Within these corridors, specific line routes can be defined on .the map and profiles of these lines are automatically generated for detailed analysis. Before mapping is produced points with known coordinates are established throughout the area to control the photographs both horizontally and vertically. Each of the various components of route survey under this technique are discussed in following paras.
( I
I I ~
'1(\
~ ~ ...
I~
t1.
1.1.1.' Initial Survey Under initial survey, one or more preliminary transmission corridors are established. These are established with the help of Topo sheets of the region and after having a walkover survey along the tentative route alignment. 1.1.2. Controls Control points are fixed along the route for which the latitude, longitude and elevations are accurately known. An initial reconnaissance will establish the most suitable sitesfor the control points based on terrain conditions. Control points need not be proposed along the transmission line corridors, they can be at the sides of roads or elsewhere they cause the minimum impact on the land owners. Each of these points is to have a permanent marker placed on the ground. This is because the field staff is required to return to the same points again and again during the execution period of the project. Two types of permanent markers are used. For the preliminary control, a concrete cylinder is placed approximately 6 ft in the ground with the top of the cylinder flush with the surface. This is used for the 8 to 10 points which are surveyed using doppler satellite techniques. Concrete markers are installed along the proposed route to provide the overall basis for the control net work. A receiver is placed on each control point to monitor the position of satellite. From this information, position coordinates are calculated for the receiver locations on the ground. The remaining points are surveyed using the Inertial
Survey system which coordinate the control points (in x, y and z) between any two of the previously established doppler points. For these points, a 4 ft long steel bar is driven in the ground so that the top is flush with the surface. Inertial Survey System is operated from a helicopter in order to produce large number of coordinated points in a minimum amount of time.
1.1.3
Orthophoto Mapping
Aerial survey mapping (photogrammetry) has a definite application to the planning and design of transmission lines and is used in the advanced countries both in the preliminary stages of line routing and in the preparation of plan and profile maps for structure plotting. Aerial photography is taken immediately after fixing the control points along the tentative route alignment in order to minimise the loss of targets due to weather or any other problems. Here it is necessary that these control points show up very clearly when the aerial photography is taken. Orthophoto is a photograph of the area which is true to scale in all respects. It gi~es the transmission line engineer a complete picture of all ground features with the added bonus of the required vertical pata. It is produced from aerial photography using compJier technique. :"
A band, approximately,2 kms wide is generally mapped along the preliminary corridors. The horizontal scale for the mapping is 1: I0,000 with 1 m contour intervals in the plain section and 5 mcontour in the mountaneous terrain. This gives a gOod basis for selection of tower site with spot height accuracy to within 1 to 2 metres. Some of the specific advantages of using photogrammetry techniques for transmission line survey-are as under:
1.1.4 Advantages Determine:J.the best route: The broad coverage provided by aerial photographs facilitate selection of best line route. Potential routing difficulties can be recognised and avoided before any field activity begins. Also angles can be selected easily for efficient and economical use of structures.
1.15
Economical Aerial surveying has definite economic advantages-both in respect of time and cost. Where mountaineous/rugged terrain, inaccessible swamp land or heavily populated areas are encountered, even greater economies can be realised.
1.1.6
Saves\ Times Data that could take months to obtain by ground survey can be obtained by aerial survey in a much shorter period of time.
/!
54 1.1.7 Greater Visual Details. The use of photogmmmetry techniques provides tisual detaiis as well as pennanent visual record of existing features which can not be obtained byany other means.· 1.1.8 More Accurate Engineering. Design & Construction
Bids Accurate plan and profile maps can be prepared from .photographic enlargement; which hel p the designers to spot the tower~ and design the footing with greater accuracy and " economy.
1.1.9 Flexibility All necessary.line data, including tower spoUing profiling etc. can be detennined from theorthophotos for any number of ro.ute· variation~ withOl,lt returning to the actual site. In fact, changes in the rOute alignment can be made with the mini·mum . difficulty.
1.1.10 .Confidential Aerial surveys are confidential and therefore help in minimising the way leave problems. 1.1.11
Equipment required and their cost
Equipment required/or Satellite Doppler Technique are: Equipment for control surveys i.e., Satellite doppler global position system, Inertial survey system and Electronic distance measurement system. Equipment for aerial photography i.e. Aeroplane, Camera & PhoLOmechanicallaboratory. Mapping equipment-Analytical stereo compilers. Cost of these equipments is definitely substantially high and as such initial investment for acquiring the same is much more. In regard to the operational cost, it may vary due to geographic location, distance from aerial survey station to job site, type of aircraft employed, quality of photography and degree of accuracy required.
i
I
~. :, .
I \
The e'quipoise
A mandate for balance To strike ahead for a more optimum system of bulk power distribution, POWERGRID was incorporated in October,1989. The formation of POWERGRID is merely the reorganisation of the Power Sector in the pursuit of a more efficient. planning, implementation and development of power for the country. With the amalgamatjon of available expertise inJhe areas of Transmission, Load Despatch and Communications, . POWERGRID is poised to set the milestones towards a reliable, economic and secure National Power Grid.
(A Government of India Enterprise) Regd. Off. Hemkunt Chambers, 10th Floor, 89 Nehru Place,New Delhi _ 110019. ",.~----------~-.-
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