DESIGNING OF STEEL PIPERACK
A PROJECT REPORT Submitted by
JAYENDRAVEL.S KESAVRAMAN.S LARSEN SAMUEL.S MOHAMED MUZAMIL.B.A MOHAMED SATHIR.M
In partial fulfillment for the award of the degree of
BACHELOR OF TECHNOLOGY in
CIVIL ENGINEERING
BHARATH INSTITUTE OF SCIENCE AND TECHNOLOGY BHARATH UNIVERSITY CHENNAI-600 073 APRIL-2011 1
BHARATH UNIVERSITY CHENNAI-600 073 BONAFIDE CERTIFICATE Certified that this project report
“DESIGNING OF STEEL PIPE RACK” Is the
bonafied work of “ JAYENDRAVEL.S (U07CE058), KESAVRAMAN.S (U07CE071), LARSEN SAMUEL.S (U07CE078), MOHAMED MUZAMIL.B.A (U07CE094), MOHAMED SATHIR.M
SIGNATURE
(U07CE096)”
SIGNATURE
S.SANKARAN
Mr.T.P.MEIKANDAAN
HEAD OF THE DEPARTMENT,
SUPERVISOR,
CIVIL ENGINEERING,
CIVIL ENGINEERING,
BHARATH UNIVERSITY,
BHARATH UNIVERSITY,
CHENNAI - 600 073.
CHENNAI - 600 073.
EXTERNAL EXAMINER
INTERNAL EXAMINER
2
ACKNOWLEDGEMENT
We thank our beloved Chancellor Er. J.Sundeep Aanand for his commendable support in the achievement of this project with success.
We thank our Vice Chancellor Dr. K.P.Thooyamani for creating an atmosphere where we can develop our academic skills.
We are privileged to thank our Principal Dr. R.Kari Thangaratnam for the facilities extended to us during this course.
We would like to extend our sincere thanks to our guide Mr.T.P.Meikandaan (Sr.Lecturer) Civil Engineering Department who has given valuable support during the course of our project by clarifying our doubts and guiding with his novel ideas.
We wish to express our sincere thanks to Dr.S.Sankaran, Professor and Head of department of civil engineering, Mr.P.Dayakar (Asst.Prof), Mr.P.Sachinantham (Asst.Prof), and and all other staff members for their valuable encouragement and guidance during the tenure.
We extent our thanks to all the non-teaching staff of Civil Engg Dept those who helped us in completing this project successfully.
3
ABSTRACT It is common to overemphasize the structural design of pipe support structures, rather than focus on Detailing for stability or economics and practical aspects of the steel structure and the foundations. This is sometimes referred to as over-designing and under-detailing. Sometimes the hanger-type pipe Supports or the trapezes supported by another structure, such as the main building frame, are referred to as pipe support structure. For the purposes of this discussion, the terms pipe racks, pipe supports, and pipe support structures are interchangeable. Essential elements for limit states of pipe support systems are often ignored, since these systems are comprised of secondary elements and rarely impact the structural integrity of any industrial facility. Structural failures of pipe supports are neither documented nor disseminated to the structural community. The structural design of pipe racks varies widely depending of pipe racks varies sidely. Depending upon the plant operations and the associated plant standards. However, pipe rack failures could cause serviceability problems for plant operations. Failures of pipe support system could potentially impact the health, welfare, and safety of plant personnel die to pipe breakage or leaks. The Following discussion includes a review of the considerations involved in the design, detailing, and structural stability of pipe racks. Optimal solutions are still governed by the judgment of design engineer.
4
TABLE OF CONTENTS CHAPTER
TITLE
PAGE
NO.
NO. ACKNOWLEDGEMENT
1
i
ABSTRACT
ii
LIST OF TABLES
vii
LIST OF FIGURES
viii
LIST OF ABBREVIATION
ix
INTRODUCTION
1
1.1 GENERAL
1
1.2 SCOPE
1
1.3 TERMINOLOGY
1
1.3.1 Structure
2
1.3.1.1 Main Cross Beam
2
1.3.1.2 Portal Frame
2
1.3.1.3 Longitudinal Beam
2
1.3.1.4 Width of Piperack
2
1.3.1.5 Piperack Spacing
2
1.3.1.6 Intermediate cross beam
2
1.3.1.7 Longitudinal stability
2
1.4 FOUNDATIONS
3
1.4.1 Footing
3
5
2 3
1.4.2 Longitudinal Beam
3
1.5 TYPES OF PIPE RACK
4
1.5.1 Conventional Pipe Rack
4
1.5.2 Non Continuous Pipe Rack
4
1.5.3 Modular Pipe Rack
4
LITERATURE REVIEW DESIGN PROCEDURE
6 7
3.1 CONVENTIONAL PIPE RACK
7
3.1.1 Data Collection For Pipe Rack Design
7
3.1.2 Design Loads Consideration
8
3.1.3 Load Combinations And Allowable Deflection Of Pipe Rack
4
13
3.1.4 Final Anchor And Guide Load Check
15
3.1.5 Allowable Horizontal And Vertical Deflection
15
3.1.6 Framing Of Continuous/Conventional Piperack
15
LOAD CALCULATION
19
4.1 PIPE LOAD
19
4.2 WIND LOAD CALCULATIONS AS PER IS 875-3
26
4.2.1 Wind load calculation for the second frame in grid 1&2 - (X - Direction) 4.2.2 Wind Load applied in (Z - Direction) 90 Degree
27 28
4.2.3 Wind load calculation for the frame in grid A - (Z - Direction)
29
4.2.4 Wind load calculation for the second frame in grid B - (Z - Direction)
6
30
5
DESIGN OF BASE PLATE
33
5.1 LOADING
33
5.2 DESIGN FOR TENSION
34
5.3 DESIGN FOR COMPRESSION
34
5.4 DESIGN OF BOLTS SUBJECTED TO SHEAR AND TENSION 35
6
7
5.5 CALCULATIONS
35
DESIGN OF PEDESTAL
37
6.1 PEDESTAL MARK
37
6.2 CALCULATION OF Nuz and K
39
6.3 SECTION DESIGN - RATIOS FOR CHART ENTRY
40
Design of Combined Foundation
41
7.1 DESIGN OF COMBINED FOUNDATION "F1"
41
7.1.1 Longitudinal direction ( Z - dir )
43
7.1.2 Transverse direction ( X - dir )
44
7.1.3 Pressure Along Z - Direction
45
7.1.4 Load calculations for combined Footing “F1”
47
7.1.5 Design of Strap Beam
50
7.1.6 Check For Shear
51
7.2 DESIGN OF COMBINED FOUNDATION "F2"
52
7.2.1 Longitudinal direction ( Z - dir )
54
7.2.2 Transverse direction ( X - dir )
55
7.2.3 Pressure Along Z - Direction
56
7.2.4 Load calcu lations for combined Footing “F2”
58
7.2.5 Design of Strap Beam
61
7.2.6 Check For Shear
62 7
8
CONCLUSION
63
REFERENCE
64
8
LIST OF TABLES
TABLE NO.
4.1
TITLE OF THE TABLE
Load Calculation For Pipe Load
9
PAGE NO.
19
LIST OF FIGURES
FIGURE NO.
4.1
TITLE OF THE FIGURE
PAGE NO.
Shows The Pipe Bridge Is Analysed Using A Structural Software Program Staad Pro
20
4.2
The Nodes Numbers Of The Pipe Rack
21
4.3
The Beam Numbers Of The Pipe Rack
22
4.4
The Top Plan View Of The Pipe Rack
23
4.5
The View Of Pipe Rack
23
4.6
Shows The Grid 1 And Grid 2 Of The Pipe Rack
24
4.7
The Vertical Pipe Load Of The Pipe Rack
25
4.8
The Wind Load Applied On The Grid 1 And 2
27
4.9
The Wind Load Applied In (Z-degree)
28
4.10
The Wind Load For The Frame A In (Z-direction)
29
4.11
The Wind Load For The Frame B In (Z-direction)
30
4.12
Shear Force Diagram At (Z-direction)
32
4.13
Shear Force Diagram At (Y-Direction)
32
4.14
Bending moment at (Z-direction)
33
4.15
Bending moment at (Y-direction)
33
10
LIST OF SYMBOLS AND ABBREVATIONS
SYMBOLS
DESCRIPTION
A
Total area of section.
Ab
Equivalent area of helical reinforcement.
Ac
Area of compressive steel.
Ae
Equivalent area of section.
Ak
Area of concrete core.
Am
Area of steel or iron core.
Asc
Area of longitudinal reinforcement (comp.)
Ast
Area of steel (tensile).
Al
Area of longitudinal torsional reinforcement.
Asv
Total cross-sectional area of stirrup legs or bent up bars within distance s v.
Aw
Area of web reinforcement.
AФ
Area of cress-section of one bar.
a
Lever arm.
ac
Area of concrete.
B
Flange width of T-beam.
b
Width.
br
Width of rib.
C
Compressive force.
c
Compressive stress in concrete.
c’
Stress in concrete surrounding compressive steel.
cs
Permissible tensile stress in concrete.
c1
Compressive stress at the junction of flange and web. 11
D
Depth.
d
Effective depth.
d c
Cover to compressive steel.
d s
Depth of slab.
d t
Cover to tensile steel.
e
Eccentricity. Compressive steel depth factor (=d c /d).
F
Shear force,
F r
Radial shear force.
f
Stress (in general).
f ck
Characteristic compressive stress.
f y
Characteristic strength of steel.
H
Height.
I
Moment of inertia.
I e
Equivalent moment of inertia of section.
j
Lever arm factor.
K a
Coefficient of active earth pressure.
K p
Coefficient of passive earth pressure.
k
Neutral axis depth factor (n/d).
L
Length.
Ld
Development length.
M
Bending moment.
M r
Moment of resistance.
M t
Torsional moment.
M θ
Circumferential bending moment. 12
m
Modular ratio.
n
Depth of neutral axis.
nc
Depth of critical neutral.
∑0
Sum of perimeter of bars.
Pa
Active earth pressure.
P p
Passive earth pressure.
Pu
Ultimate load.
P
Percentage steel.
P’
Reinforcement ratio ( Au /bd).
pa
Active earth pressure intensity.
pe
Net upward soil pressure.
pa
Passive earth pressure intensity.
Q
Shear resistence.
q
Shear stress (due to bending).
’
q
Shear stress due to torsion.
R
Radius ; Resistance factor (=½ cjk).
r
Radius ; cost ratio of steel and concrete ; L/B ratio.
s
Spacing of bar ; standard deviation.
sa
Average bond stress.
sb
Local bond stress.
T
Tensile force ; Thickness of wall ; Torsional moment.
t
Tensile stress in steel. ’
t c
Compressive stress in compressive steel.
W
Point load ; Total load.
X
Co – ordinate. 13
Z
Distance; Co-ordinate.
α
Inclination; coefficient.
β
Surcharge angle.
γ
Unit weight of soil.
γ’
Submerged unit weight of soil.
σ cc
Permissible stress in concrete (direct comp).
σ cc’
Direct compressive stress in concrete.
σ cbc
Permissible compressive stress in concrete due to bending.
σ st
Permissible stress in steel in tension.
σ st
Permissible tensile stress in shear reinforcement.
σ st
Permissible tensile stress in main reinforcement.
σ sy
Yield point compressive stress in steel.
μ
Coefficient of friction.
τ c
Shear stress.
Ф
Diameter of bar.
τ cmax
Max. Shear stress.
τ v
Nominal shear stress.
14
CHAPTER – 1 INTRODUCTION 1.1 GENERAL
Pipe rack is the main artery of any plant. This carries the pipes and cable trays (raceways) from one equipment to another equipment within a process unit (called ISBL piperack) or carries the pipe and cable trays from one unit to another unit (called OSBL pipe rack). Sometimes you will also find the air cooled heat exchangers on the pipe rack. 1.2 SCOPE
This design guide defines the minimum requirements for the design of piperack in process industry facilities at the sites. It covers general design philosophy and requirements to be used in the analysis and design of piperack. Criteria presented herein pertain to loads, load combinations, allowable stresses, and superstructure and foundation design. 1.3 TERMINOLOGY
Piperack is a structure made of steel, concrete or mixed supporting :-
One or more layers of piping.
-
Electrical or instrument cable tray.
-
Air cooler in certain case.
Piperack comprises of two parts :-
Steel or concrete structure.
-
Concrete foundation.
A piperack composes of various element with the following terminology :-
15
1.3.1 Structure 1.3.1.1 Main Cross Beam
The main cross beam is a horizontal beam connected to two posts to form the portal frame and to support the pipes. 1.3.1.2 Portal Frame
The element of piperack forms by two posts and one or more main cross beams. 1.3.1.3 Longitudinal Beam
The longitudinal beam is a horizontal beam connecting two portal frame in longitudinal direction. Generally, the members are used to support the lateral forces, intermediate cross beams and post of coolers. Especially to transmit the horizontal force to the bracing bay. 1.3.1.4 Width of Piperack
The width of piperack is the distance between the axis of the posts. 1.3.1.5 Piperack Spacing
Piperack spacing is the distance between the portal frames. 1.3.1.6 Intermediate cross beam
The intermediate cross beam is a horizontal cross members supported by longitudinal beams. They are used to reduce the deflection of small pipes. Their requirement is decided by piping department. The intermediate cross beam shall be steel. 1.3.1.7 Longitudinal stability
Longitudinal stability forms by two consecutive portal frame connected by members which restraint the longitudinal forces.
16
1.4 FOUNDATIONS 1.4.1 Footing
Footing is a member rest on good ground, in the case of pile this is called pipe cap. 1.4.2 Longitudinal Beam
Longitudinal beam is a beam connecting the two consecutive footing in longitudinal direction. -
Longitudinal beam incorporated with the footing.
-
Longitudinal beam rested on the footing.
17
-
Longitudinal beam semi-incorporated with the footing.
1.5 TYPES OF PIPE RACK
•
Continuous Piperack (conventional pipe rack) system
•
Non-continuous Piperack system
•
Modular Piperack
1.5.1 Conventional / Continuous Pipe rack
Continuous Piperack (conventional pipe rack) system: This is essentially a system where multiple 2-dimensional (2D) frame assemblies (commonly called bents), comprised of two or more columns with transverse beams, are tied together in the longitudinal direction utilizing beam struts (for support of transverse pipe and raceway elements and for longitudinal stability of the system) and vertical bracing to form a 3D space frame arrangement. Piperacks supporting equipment such as air-cooled heat exchangers must utilize the continuous system approach. 1.5.2 Non- Continuous Pipe rack
This is a system comprised of independent cantilevered, freestanding 2D frames not dependent on longitudinal beam struts for system stability. This system, where feasible, should result in lower total installed cost (TIC). 1.5.3 Modular Pipe rack
Building Modules: Structural Frames completely fitted with miscellaneous equipment and architectural finishes.
18
Piperack Modules: Structural Frames completely fitted with pipes, Cable trays and miscellaneous equipment.
19
CHAPTER – 2 LITERATURE REVIEW Kasi V. Bendapudi, P.E., S.E. Structural steel pipe supports are extensively utilized in
industrial and manufacturing facilities. Lack of uniform industry standards for this topic leads to each organization adopting its own engineering standards, at times, without a clear understanding of the underlying theoretical concepts and the cost implications. This is the first of a two-part series of articles on the behavior and design of steel support structures for pipes. This article discusses the effects of ambient temperature changes, expansion joint requirements, and an introduction to design loads. Part 2 concludes with the continuation of design loads, structure stability concepts and detailing for stability requirements. It is common to overemphasize the structural design of pipe support structures, rather than focus on detailing for stability or economics and practical aspects of the steel structure and the foundations. This is sometimes referred to as "overdesigning" and "under-detailing". Sometimes the hanger-type pipe supports or the trapezes supported by another structure, such as the main building frame, are r eferred to as "pipe support structures.
Frank E. Richart. Publication: Journal Proceedings. In these tests, major emphasis has
been placed on the combined column footing. Principal attention has been given to the resistance of footings to failure by bond, diagonal tension and tension in the steel. Taylor and francis.January 29, 2008 ; The principal features of the new edition is the
discussion of behavior of the steel structures and exemplify details of the design process.
20
CHAPTER – 3 DESIGN PROCEDURE 3.1 CONVENTIONAL / CONTINUOUS PIPE RACK
Continuous Piperacks (conventional pipe rack) system: This is essentially a system where multiple 2-dimensional (2D) frame assemblies (commonly called bents), comprised of two or more columns with transverse beams, are tied together in the longitudinal direction utilizing beam struts (for support of transverse pipe and raceway elements and for longitudinal stability of the system) and vertical bracing to form a 3D space frame arrangement. Piperacks supporting equipment such as air-cooled heat exchangers must utilize the continuous system approach. 3.1.1 Data collection for pipe rack design
Due to
the “fast track” nature associated with most of the projects, often the final piping,
raceway, and equipment information is not available at initiation of the piperack design. Therefore, as a Civil/Structural Engineer, you should coordinate with the Piping group, Electrical, Control Systems, and Mechanical groups to obtain as much preliminary information as possible. When received, all design information should be documented for future reference and verification. In the initial design, the Engineer should use judgement when applying or allowing for loads that are not known, justifying them in the design basis under "Design Philosophy". The following should be reviewed for design information:
•
Plot plans and equipment location plans
•
3D model showing piping layout, cable tray layout, Piperack bent spacing and
elevation of support levels in the transverse direction , Elevation of longitudinal beam struts and locations of vertical bracing. and location of pipe bridge, if any.
•
Piping orthographic drawings.
•
Vendor prints of equipment located on the rack, e.g., air coolers and exchangers.
The vendor prints should include the equipment layout, mounting locations and details, access 21
and maintenance requirements, and the magnitude and direction of loads being transmitted to the piperack.
•
Electrical and control systems drawings showing the routing and location of
electrical and instrumentation raceways and/or supports.
•
Underground drawings that show the locations of buried pipes,concrete structures
and foundations, duct banks, etc. in the area of the piperack.
•
Pipe rack construction material (Steel, Cast-in-situ concrete, Pre-cast concrete)
shall be as per project design criteria. Please note that, Unless specifically explained in the project design criteria, no allowance or provisions should be made for future additions for pipe or raceway space and related loading. 3.1.2 Design loads consideration
Following loads are to be considered for the pipe rack design: Piping Gravity load (D): In the absence of defined piping loads and locations, an assumed minimum uniform pipe load of 2.0 kPa should be used for preliminary design of piperacks. This corresponds to an equivalent load of 6 in (150 mm) lines full of water covered with 2 in (50 mm) thick insulation, and spaced on 12 in (300 mm) centers. This assumption should be verified based on coordination with the Piping Group, and concentrated loads should also be applied for any anticipated large pipes. When the actual loads and locations become known, as the project develops, the structural design should be checked against these assumed initial load parameters and revised as required. A concentrated load should then be added for pipes that are 12 in (300 mm) and larger in diameter. The concentrated load P should be: P =(W - s x p x d),
s = Spacing of piperack bent, p = pipe weight considered (kPa), d = pipe
diameter W = pipe concentrated load. Where consideration of uplift or system stability due to wind or seismic occurrences is required, use 60% of the design gravity loads as an "all pipes empty" load condition.
22
Loading due to hydrostatic testing of lines should be considered in the design if applicable. Coordinate the testing plan(s) with Construction, Startup, and/or the Piping Group as necessary, in order to fully understand how such loads will be applied to the piperack structure. Under most normal conditions, multiple lines will not be simultaneously tested. The hydro-test loads do not normally need to be considered concurrently with the other non-permanent loads, such as live load, wind, earthquake, and thermal. Typical practice is to permit an overstress of 15% for the hydro-test condition. Because of these considerations, the hydro-test condition will not normally govern except for very large diameter pipes. Electrical Tray and Conduits (D): Electrical and control systems drawings and/or the project 3D model should be reviewed to determine the approximate weight and location of electrical trays, conduits, and instrumentation commodities. Unless the weight of the loaded raceways can be defined, an assumed minimum uniform load of 1.0 kPa should be used for single tier raceways. Self weight of Pipe rack (D): The weight of all structural members, including fireproofing, should be considered in the design of the piperack. Weight of Equipment on pipe rack (D): Equipment weights, including erection, empty, operating, and test (if the equipment is to be hydro-tested on the piperack) , should be obtained from the vendor drawings. The equipment weight should include the dead weight of all associated platforms, ladders, and walkways, as applicable. Special Loads: Special consideration should be given to unusual loads, such aslarge valves, expansion loops, and unusual piping or electrical configurations. Live Load (L): Live load (L) on access platforms and walkways and on equipment platforms should be considered, as applicable. Wind Load (W): Transverse wind load on structural members, piping, electrical trays, equipment, platforms, and ladders should be determined in accordance with project approved design code. Longitudinal wind should typically be applied to structural framing, cable tray vertical drop (if any), large dia pipes vertical drop (if any) and equipment only. The effects of longitudinal wind on piping and trays running parallel to the wind direction should be neglected.
23
Friction Loading (Tf): Friction forces caused by hot lines sliding across the pipe support during startup and shutdown are assumed to be partially resisted through friction by nearby cold lines. Therefore, in order to provide for a nominal unbalance of friction forces acting on a pipe support, a resultant longitudinal friction force equal to 7.5% of the total pipe weight or 30% of any one or more lines known to act simultaneously in the same direction, whichever is larger, is assumed for piperack design. Friction between piping and supporting steel should not be relied upon to resist wind or seismic loads. Anchor and Guide Loads (Ta): Piperacks should be checked for anchor and guide loads as determined by the Pipe Stress Group. It may be necessary to use horizontal bracing if large anchor forces are encountered. For conventional pipe rack systems, it is normally preferred to either have the anchors staggered along the piperack so that each support has only one or two anchors, or to anchor most pipes on one braced support. For initial design, when anchor and guide loads are not known, use a longitudinal anchor force of 5.0 kN acting at midspan of each bent transverse beam (refer project design criteria). Guide loads are usually small and may be ignored until they are defined by the Pipe Stress Engineer.
For non-continuous pipe rack
systems, piping may be transversely guided or anchored at both cantilever frames and anchor bays. Longitudinal anchors may be located only at anchor bays. LOAD COMB 1 DL+WL(+X) LOAD COMB 2 DL+WL(-X) LOAD COMB 3 DL+WL(+Z) LOAD COMB 4 DL+WL(-Z) LOAD COMB 5 DL+LL LOAD COMB 6 DL+LL+FLX+FLZ LOAD COMB 7 DL+LL-FLX-FLZ LOAD COMB 8 DL+LL-FLX+FLZ LOAD COMB 9 DL+LL+FLX-FLZ
24
********FOUNDATION DESIGN******** LOAD COMB 10 DL+LL+FLX+FLZ+WLX LOAD COMB 11 DL+LL+FLX+FLZ-WLX LOAD COMB 12 DL+LL+FLX+FLZ+WLZ LOAD COMB 13 DL+LL+FLX+FLZ-WLZ LOAD COMB 14 DL+LL-FLX-FLZ+WLX LOAD COMB 15 DL+LL-FLX-FLZ-WLX LOAD COMB 16 DL+LL-FLX-FLZ+WLZ LOAD COMB 17 DL+LL-FLX-FLZ-WLZ LOAD COMB 18 DL+LL-FLX+FLZ+WLX LOAD COMB 19 DL+LL-FLX+FLZ-WLX LOAD COMB 20 DL+LL-FLX+FLZ+WLZ LOAD COMB 21 DL+LL-FLX+FLZ-WLZ LOAD COMB 22 DL+LL+FLX-FLZ+WLX LOAD COMB 23 DL+LL+FLX-FLZ-WLX LOAD COMB 24 DL+LL+FLX-FLZ+WLZ LOAD COMB 25 DL+LL+FLX-FLZ-WLZ ********FOR MEMBER DESIGN******** LOAD COMB 26 DL+LL+FLX+FLZ+WLX LOAD COMB 27 DL+LL+FLX+FLZ-WLX LOAD COMB 28 DL+LL+FLX+FLZ+WLZ
25
LOAD COMB 29 DL+LL+FLX+FLZ-WLZ LOAD COMB 30 DL+LL-FLX-FLZ+WLX LOAD COMB 31 DL+LL-FLX-FLZ-WLX LOAD COMB 32 DL+LL-FLX-FLZ+WLZ LOAD COMB 33 DL+LL-FLX-FLZ-WLZ LOAD COMB 34 DL+LL-FLX+FLZ+WLX LOAD COMB 35 DL+LL-FLX+FLZ-WLX LOAD COMB 36 DL+LL-FLX+FLZ+WLZ LOAD COMB 37 DL+LL-FLX+FLZ-WLZ LOAD COMB 38 DL+LL+FLX-FLZ+WLX LOAD COMB 39 DL+LL+FLX-FLZ-WLX LOAD COMB 40 DL+LL+FLX-FLZ+WLZ LOAD COMB 41 DL+LL+FLX-FLZ-WLZ Please note that, all friction forces and anchor forces with less magnitude, (say ~ 5.0 kN), applied to the top flange of the beam, may be considered as resisted by the total beam section. When anchor loads have large magnitude and are applied to the top flange of the beam, the effect of torsion must be addressed. If the beam section is inadequate to take care of this torsional force, alternatives to be considered, such as provide horizontal bracings at the load locations. 3.1.3 Load Combinations and allowable deflection of pipe rack
You need to create the load combinations per your project design criteria. However, I have referred here some load combinations. Please note the following:
•
Earthquake load is a factored load. 26
•
For load combinations that include wind or earthquake loads, use only the non-
friction portion (anchor and guide portion) of the thermal loads, i.e., friction loads are not combined with wind or seismic loads. Friction loads are considered to be self-relieving during wind and earthquake and should only be combined with anchor and guide loads when wind or earth-quake loads are not considered.
•
Hydrostatic test loads need not be combined with wind and earthquake loads
unless there is a reasonable probability of the occurrence of either of these loads during hydrostatic testing. For calculation of foundation soil bearing pressures or pile loads, stability checks against overturning, sliding, and buoyancy, and deflection checks, the following unfactored load combinations (ACI 318) shall be used: 1.
D
2.
D + L + SL + Tf + Ta
3.
D + Tf + Ta
4.
D + 1.3W + Ta
5.
D + L + 0.5SL + 1.3W +Ta
6.
D + L + S +0.65W + Ta
7.
0.9De + 1.3W + Ta
8.
D + E/1.4 + Ta
9.
D + 0.2S + E/1.4 + Ta
10. 0.9De + E/1.4 + Ta
27
Load Combinations for design of foundations
1.
1.4D
2.
1.4D + 1.7L +1.7S
3.
1.4D + 1.4Tf +1.4Ta
4.
0.75 (1.4D + 1.7L + 1.7S + 1.4Tf + 1.4Ta)
5.
0.75 (1.4D + 1.7L + 1.7S + 1.4Ta) + 1.6W
6.
1.2D + 0.2S + 1.0E + 1.2Ta
7.
0.9De + 1.6W + 1.2Ta
8.
0.9De + 1.0E + 1.2Ta
Steel Design load combinations
1.
1.4D
2.
1.2D + 1.6L + 0.5S + 1.2Tf + 1.2Ta
3.
1.2D + 1.6S + 0.5L + 1.2Tf + 1.2Ta
4.
1.2D + 1.6S + 0.8W + 1.2Ta
5.
1.2D + 1.6W + 0.5L + 0.5S + 1.2Ta
6.
1.2D + 1.0E + 0.5L + 0.2S + 1.2Ta
7.
0.9De + 1.6W + 1.2Ta
8.
0.9De + 1.0E + 1.2Ta
De is the minimum dead load on the structure.
28
3.1.4 Final anchor and guide load check
Where the design of transverse beams has been based on anchor loads as explained in design load consideration final check of beams (and other affected members) should be made when final definition of these loads is available from the Pipe Stress Engineer. Based on the Engineer's experience and judgement, an overstress in any element (of up to 10%) can be considered, provided proper justification is given. Where such overstress cannot be properly justified, modifications should be made to the piperack structure in order to bring the stress levels within the normal allowables.
Modifications could entail the addition of horizontal
bracing to the transverse beams to resist significant loads from the anchor(s), replacing and/or adding members, strengthening members (i.e.,cover plating, etc.), and/or relocating the anchor and guide load(s). 3.1.5 Allowable horizontal and vertical deflection
Allowable deflections of piperack structures shall be as per project design criteria. However, you can consider the following as limit of deflection:Lateral deflection produced by load combinations that include wind or seismic forces:Piperacks supporting equipment: h/100, unless a more stringent requirement is given by the manufacturer of the equipment. Piperacks supporting piping and raceway only: h/200 or as per project design criteria.Lateral deflection produced by sustained static forces such as pipe and anchor loads: h/200 or as per project design criteriaVertical deflection of beams due to gravity pipe loads:as per project design criteria h is the total height of the pipe rack structure. 3.1.6Framing of continuous/conventional pipe rack Frames
Main piperacks are usually designed as moment-resisting frames in the transverse direction.
In the longitudinal direction, there should be at least one continuous level of beam
struts on each side. For piperacks with more than one tier, the beam struts should be located at a level that is usually equal to one-half tier spacing above or below the bottom tier. Vertical bracing in the longitudinal direction should be provided to carry the longitudinal forces, transmitted through the beam struts, to the baseplate / foundation level.
29
Transverse Beam
Transverse beams must be capable of resisting all forces, moments, and shears produced by the load combinations. Transverse beams are generally a moment-resisting frame, modeled and analyzed as part of the frame system. The analysis model must reflect the appropriate beam end conditions. In the design of beams, consideration should be given to
•
Large pipes that are to be hydro-tested.
•
Anchor and friction load with large magnitude (see step-2, anchor and friction
load) Central Spine
For steel piperacks with spans of more than 6 m, a center spine consisting of a system of horizontal braces and struts located at midspan of each level of piping should be considered. This additional light horizontal framing greatly increases the capacity of the transverse pipe support beams to resist friction and anchor forces, and also serves to reduce the unbraced length of the beam compression flange in flexure and to reduce the unbraced length of the beam about the weak-axis in axial compression. This concept reduces the required beam sizes and provides a mechanism for eliminating or minimizing design, fabrication, or field modifications that could otherwise be required due to late receipt of unanticipated large pipe anchor forces. Longitudinal Beam Strut
For typical continuous piperack systems, the longitudinal beam struts should be designed as axially loaded members that are provided for longitudinal loads and stability. Additionally, the longitudinal beam struts that support piping or raceway should be designed for 50% of the gravity loading assumed for the transverse pipe or raceway support beams, unless unusual loading is encountered. This 50% gravity loading will account for the usual piping and raceway take-offs. Normally, the gravity loading carried by the beam struts should not be added to the design loads for the columns or footings since pipes or raceway contributing to the load on the beam struts would be relieving an equivalent load on the transverse beams.
30
For any continuous piperack system where the anticipated piping and raceway take-offs are minimal or none, the 50% loading criteria does not apply. In such cases, the beam struts should be designed primarily as axially loaded members. Do not provide beam struts if they are not needed for piping or raceway support, or for system stability. Conversely, the 3D model should be checked to verify that beam struts subjected to unusually large loads (such as at expansion loops) have been given special consideration. All longitudinal beam struts, including connections, should be designed to resist the axial loads produced by the longitudinal forces. When designing the longitudinal beam struts for flexural loads, the full length of the beam should be considered as the unbraced length for the compression flange. Vertical Bracing
When moment-resisting frame design is not used in the longitudinal direction, vertical bracing should be used to transmit the longitudinal forces from the beam struts to the foundations. Knee-bracing or K-bracing is most often used for this purpose. Unless precluded by equipment arrangement or interferences, bracing should be placed equidistant between two expansion joints.
Design calculations and drawings must reflect a break in the beam strut
continuity between adjacent braced sections through the use of slotted connections or by eliminating the beam struts in the bays designated as free bays. The maximum length of a braced section should be limited to 48m to 50m. If the braced bay is not located equidistant from the free bays, the maximum distance from the braced bay to a free bay should be limited such that the maximum total longitudinal growth or shrinkage of the unrestrained segment does not exceed 40 mm. Column
The columns must be capable of resisting all loads, moments, and shears produced by the load combinations.A moment-resisting frame analysis should normally be used to determine the axial load, moment, and shear at points along the columns.The frame analysis model should be based on the following:
•
Consider column base as hinge.
•
Use 4 bolt connections for safety purpose 31
For design of steel columns subjected to flexural loads, the distance between the base and the first transverse beam or the knee brace intersection should be considered as the compression flange unbraced length.
32
CHAPTER – 4 LOAD CALCULATION 4.1 PIPE LOAD
Load Calculation for 2", 6", 12" & 16" diameter pipe (Pipe weight + Pipe filled with oil) As per the load data obtained from the piping input, the loads for the pipes are as tabulated below: Table-4.1 Load Calculation For Pipe Load
Weight of Pipe (Kg/m)
Weight of oil (Kg/m)
Weight of Pipe x Nos (Kg/m)
Weight of water x Nos (Kg/m)
Weight of water + Weight of Pipe (Kg/m)
Total weight (kg/m)
Pipe Dia (inches)
No of Pipes
2"
1
7.47
2.53
7.47
2.53
10.00
10
6"
2
42.50
17.50
85
35
60.00
120
12"
1
73.80
77.20
73.8
77.2
151.00
151
16"
4
93.10
146.90
372.4
587.6
240.00
960
216.87
244.13
538.67
702.33 1241.00 Kg/m
Total =
33
461.00 12.4 KN/m
1241.00
Fig 4.1 shows the pipe bridge is analysed using a structural software program staad pro. Analysis has been carried out on the structural model considering all loads acting over the structure. Analysed for various load combinations as per code.
34
Fig 4.2 The nodes numbers of the pipe rack
35
Fig 4.3 The beam numbers of the pipe rack
36
Fig 4.4 The top plan view of the pipe rack
Fig 4.5 The view of pipe rack
37
Fig 4.6 Shows the Grid 1 and Grid 2 of the pipe rack
38
Fig 4.7 The vertical pipe load of the pipe rack
39
4.2 WIND LOAD CALCULATIONS AS PER IS 875-3
Site wind speed, Vs = Vb x Sa x Sd x Ss x Sp Site wind speed, Vs = Vb x Sa x Sd x Ss x Sp=33.5 Site wind speed, Vs = Vb x Sa x Sd x Ss x Sp=2.75 Site wind speed, Vs = Vb x Sa x Sd x S s x Sp=1+0.001*ΔS Site wind speed, Vs = Vb x Sa x Sd x Ss x Sp=1.00275 Site wind speed, Vs = Vb x Sa x Sd x Ss x Sp=1 Site wind speed, Vs = Vb x Sa x Sd x Ss x Sp=1 Site wind speed, Vs = Vb x Sa x Sd x Ss x Sp=
1
Site wind speed, Vs = Vb x Sa x Sd x Ss x Sp=33.592125 Site wind speed, Vs = Vb x Sa x Sd x Ss x Sp Effective height He=6.4 Terrain and building factor, Sb=1.6864 Effective wind speed, Ve = Vs x Sb=56.6497596 Dynamic pressure, qs Dynamic pressure, qs = 0.613 x Ve^2=1.96723669605827
Size effect factor, Ca=0.94 Net pressure coefficient (Cp) is shown in the below sections=1 Width of the building, w=4.2 Height of building, h=8 Length of building, l=30.06 Wind Pressure, Pe = qs x Cp x Ca=1.85kN/sqm
40
4.2.1 Wind load calculation for the second frame in grid 1&2 - (X - Direction)
F= force acting in a direction specified Cf = Force coefficient
1.7
Ae = Effective frontal area Pd = Design wind pressure Wind load applied over column as udl
=
0.975 kN/m
Wind load applied over Beam 1 LVL as udl
=
0.80 kN/m
Wind load applied over Beam 2 & 3 LVL as udl
=
0.31 kN/m
Wind load applied over Bracing as nodal load (1B)
=
0.81 kN
Wind load applied over Bracing as nodal load (2B)
=
0.58 kN
Wind load for bracing applied as nodal load (2B)
=
1.15 kN
Fig 4.8 The wind load applied on the grid 1 and 2
41
4.2.2 Wind Load applied in (Z - Direction) 90 Degree
Exposed Area for Column = 0.32 x 8 x 3
=
7.68 Sqm
Beam (2-3) = 0.254 x 18.55 x 1
=
4.71 Sqm
Tie = 0.09 x 18.55 x1
=
Truss = (0.09 x 3.06 x 8) + (.09*2*7) + (3.79*0.1*2)
1.67 Sqm =
4.22 Sqm
=
240.48 Sqm
24.42 Sqm Total Area
Solidity Ratio Φ Total Area
=
Exposed area Cf
= 1.9
Fig 4.9 The wind load applied in (Z-degree)
42
0.1015
4.2.3 Wind load calculation for the frame in grid A - (Z - Direction)
Wind load applied over column
=
1.090 kN/m
Wind load applied over Beam (1-2) as udl
=
0.89 kN/m
Wind load applied over Tie
=
0.35 kN/m
Wind load applied over Bracing as nodal load
=
0.48 kN
Wind load for bracing applied as nodal load @ 2 points
=
0.97 kN
Wind load for bracing applied as nodal load for stub kN
=
0.35
Fig 4.10 The wind load for the frame A in (Z-direction)
43
4.2.4 Wind load calculation for the second frame in grid B - (Z - Direction)
Wind load applied over column
=
1.090 kN/m
Wind load applied over Beam (1-2) as udl
=
0.89 kN/m
Wind load applied over Tie
=
0.35 kN/m
Wind load applied over Bracing as nodal load
=
0.48 kN
Wind load for bracing applied as nodal load @ 2 points
=
0.97 kN
Wind load for bracing applied as nodal load for stub
=
0.35 kN
Fig 4.11 The wind load for the frame B in (Z-direction)
44
Fig 4.12 Shear force diagram at (Z-direction)
Fig 4.13 Shear force diagram at (Y-direction)
45
Fig 4.14 Bending moment at (Z-direction)
Fig 4.15 Bending moment at (Y-direction) 46
CHAPTER – 5 DESIGN OF BASE PLATE 5.1 Loading
Maximum compression
=
360.01 KN
Maximum tension
=
187.67 KN
=
35
N/mm2
Permissible stress in bending comp. =
11.5
N/mm2
Permissible bearing stress
=
8.75
N/mm2
Permissible bond stress in tension
=
2.37
N/mm2
modular ratio
=
8.116
Dia of bolt Φ
=
27
mm
Total no of bolts N
=
4
nos
Permissible Axial Stress
=
240
N/mm2
Permissible shear stress
=
160
N/mm2
Base Plate details Length L
=
625
Width B
=
450
Concrete Grade of concrete fck
Bolt data
Check for compressive stress in concrete
Σc=
P/(LxB)
= =
360.008x1000/(625x450) 1.920042667 < 8.75 SAFE
47
Ref:- 0.25fck
5.2 Design for tension
Maximum tension
=
187.671 KN
No of bolts taking tension
=
4
Tension per bolt
=
70.376625 KN
Design moment M
=
WL/4
=
70.38x0.225/4
=
3.96
KNm
Allowable be nding stress σbc =
165
N/mm2
treq
6M/(bxσbc)
= =
(6x3.96x1000000)/(150x165)
=
27.06193215 mm
5.3 Design for compression
Maximum compression P
=
360.008
Base pressure
=
P/A
=
1.92 48
KN
N/mm2
Design bending moment M
treq
=
wL2/8
=
12150.27
Nmm/mm
=
6M/(bxσbc)
=
(6x12150.27)/(1x165)
=
21.01970504 mm
Provide 30mm thick base plate.
5.4 Design of bolts subjected to shear and tension
Input : Actual tension in bolts
T
=
187.67 kN
Actual shear in bolts
Fx
=
46.073 kN
Fz
=
68.352 kN
V
=
82.43 kN
Number of bolts resisting tension
Nt
=
4
Number of bolts resisting shear
Ns
=
4
Actual tension/bolt
=187.67/4
=
56.30 kN
Actual shear/bolt
=82.43/4
=
30.91 kN
Diameter of bolt
D
=
27
Number of bolts provided
n
=
4
Permissible tensile stress
stf
=
240
N/mm2
Permissible shear stress
tvf
=
160
N/mm2
5.5 Calculations
Actual tensile stress = T/(n*PI()*D^2/4*0.8) Only 80% of the bolt area taken on conservative side
49
mm
stf,cal
=56.3x1000(3.14/4x20^2x0.8)
Actual shear stress= tvf,cal
=
122.9 N/mm2
=
67.5
=
122.9/(240)+67.5/(160)
=
0.93
=
1.4
V/(n*PI()*D^2/4*0.8)
=30.91x1000/(3.14*27^2/4x0.8)
Combined stress ratio=
stf,cal/stf+ tvf,cal/tvf
Allowable stress ratio
N/mm2
SAFE
Calculation of embedment length : Grade of concrete
fck
=
35 N/mm2
Permissible bond stress
tbd
=
0.4√fcu N/mm2
=
2.37 N/mm2
Tension per bolt, Tb =
=
56.30 kN
Embedment length req =Tb/(tbd*PI()*D*0.8)
= 56.3*1000/(2.37*3.14*27*0.8) = 351 mm
Embedment length provided
=
Referring clause 3.12.8.4 of BS 8110-1
50
351
mm
CHAPTER – 6 DESIGN OF PEDESTAL 6.1 Pedestal Mark
B x
D
Design data Column Size Width, B
=
600 mm
Depth, D
=
775 mm
cover
=
40 mm
Assuming dia of bar
=
16 mm
Assuming dia of link
=
8 mm
fcu
=
35 N/Sqmm
fy
=
460 N/Sqmm
b'
=
544 mm
d'
=
719 mm
b' / B =
=
0.907
d' / D
=
0.928
51
Effective length calculation
Unsupported length, about depth
=
1.80 m
Unsupported length, about width
=
1.80 m
Effective length factor about depth
=
2
Effective length factor about width
=
2
Effective length of column about depth, Lex 2*1.8
=
3.60 m
Effective length of column about width, Lez 2*1.8
=
3.60 m
Axial load on column, N
=
360.01 kN
Force, Fx
=
46.03 kN
Force, Fz
=
68.35 kN
Initial end moment, M2x
=
123.03 kNm
Smaller initial end moment, M1x
=
0.00 kNm
Initial end moment, M2z
=
82.86 kNm
Smaller initial end moment, M1z
=
0.00 kNm
Slenderness about depth, Lex / D
=
4.65
Slenderness about width, Lez / B
=
6.00
Forces on columns
Refer staad output of member end forces
Moment about depth
Moment about width
Slenderness check
52
6.2 Calculation of Nuz and K
Balance load, Nb = 0.25 x fcu x B x D
=
4068.75 kN
Assuming ptmin = 0.4%, Asc = 0.4 x B x D / 100
=
1860 Sq
Nuz, (0.45 x fcu x Ac) +(0.95 x Asc x fy)
8136.57 kN
Reduction factor , K = (Nuz - N)/ (Nuz- Nb)
=
Hence K is limited to one K = 1 (As per Cl 3.8.3.1 of BS 8110:Part 1:1997)
1.912 1
Additional moments
About major axis = aux, K x D x (Lex/D )^2/20000.00 mm Max = N*aux
=
0.00 kNm
Mx = M2x + Max
=
123.03 kNm
About minor axis = auz = K x B x (Lez/B )^2/2000
0.00 mm
Maz = N*auz
=
0.00 kNm
Mz = M2z + Maz
=
82.86 kNm
Ratio = N / (B x D x Fcu)
=
0.022
Co-efficient Beta, β
=
0.973455631
Mx / d'
=
171117.7
Mz / b'
=
152311.8
(As per Table 3.22 of BS 8110:Part 1:1997)
As Mx / d' >Mz/b'
Mx' = Mx + Mz x β x d' / b'
= 229.64 kNm
53
6.3 Section design - Ratios for chart entry
Axial load ratio =Nratio = N / (B x D)
=
0.77
For design we have considered Maximum Moment about one axis Mz ratio = Mz' / (B x D^2)
= 0.64
d'/D
= 0.93
Actual Steel Percentage required, P(req)
= 0.80 %
Area of Reinforcement required Ast(reqd)
= 3720 Sqmm
Area of Reinfocementrequired Ast reqd. (for each face)
= 1860 Sqmm
Since Limit state stress in reinforcing steel is taken as 0.87fy in charts as against 0.95fy inEquation 1 of cl. 3.4.4.5,the modification in reinforcement area calculation is taken as below Actual Ast reqd. = 1860*0.87/0.95
=1703 Sqmm
Total area of Reinforcement
= 3407 Sqmm
Total area of Reinforcement Provided Provide
6 nos of
20
dia bars
6 nos of
20
dia bars
= 3768 Sqmm Hence o.k
Ast provided in each faces 6 -16 + 6 -16 dia bars.
54
= 3768 Sqmm
CHAPTER – 7 Design of Combined Foundation 7.1 Design of Combined Foundation "F1"
LC 30 Net SBC
SBCnet
Factor for inc in BC
106.25 kN/m2
Fbc
Joint No
1
5
7 X
PEDESTAL MARK
Col Mark
SUM 1
Z
wrt 1 0
4.2
X
wrt 1 0
0
P (kN)
Mz (kNm) Hx (kN)
0 0.00
cx1 z
z
b
cx2
-84.64 360.01
Mx (kNm) Hz (kN)
2
Cz1
x
0.00
-129.053 -60.70 -68.35 0
0.00
0.00
55.364 27.61 27.75
Pedestal Size lZ
0.6
0.6
lX
0.775 0.78
Pped
11.04 11.04
Depth of foundation from the level of point of application of forces dforc
1.3
1.3 55
Cz2
Depth of foundation below ground level (FGL) Depth of foundation below Natural Ground Level (NGL) Unit Weight of soil Projections of Footing (from centreline of column) LHS
Cz1
1.725
RHS
Cz2
1.725
Bottom
Cx1
1
Top
Cx2
1
Length of footing
l
7.650 m
Width of footing
b
2.000 m
Depth of footing
d
0.350 m
Calculations
Col Mark
SUM 1
xcor
1.725 5.925
ycor
1
2
1
Axial Load including weight of Pedestal ( Pconc = P + Pped ) Pconc 297
-73.59 371.05
Moment at base of foundation due to Horizontal Forces (Mxh = Hz * dforc )
(Mzh = Hx * dforc )
Mxh
-167.7689
-78.9113
-88.8576
Mzh
71.97
35.8943
36.0789
Moments due to Conc. Moments & Horizontal Forces (Myc = My + Myh )
(Mxc = Mx + Mxh ) 56
Mxc
-168
-78.9113
-88.8576
Mzc
72
35.8943
36.0789
Gross SBC
SBCg= Fbc * SBCnet + gs * dfngl=
Total Axial Load inclwt of pedestal (∑Pconc )
125.25 kN/m2 126kN/m2
∑P 15.3
297.4595
Area of foundation ( Provided )
A
l*b
Load due to soil
Psoil
gs*(df - d)*(A - S(lx*ly))
Weight of foundation
Fbase A*d*25
Total Vertical Load
Pv
kN
m2 177.47 kN 133.875 kN
SP + Psoil + Fbase
608.80 kN
CG of load system from bottom left corner of footing
Moments due to S(Pconc Zcor)
∑concS(∑conc Xcor)
2071.534988
297.4595
External Moments
∑Mxm
0
∑Mzm
0
Moment due to Horizontal Forces
∑Mxh
167.7689
∑Mzh
71.97
1190.89
(Psoil+Fbase)*b/2
Moment due to Soil & Raft(Psoil+Fbase)*l/2 311.3445
0 Total Moment
∑Mx 3430.20
∑Mz
680.7772
Horizontal Forces
∑Hz -129.053
∑Hx
55.364
7.1.1 Longitudinal direction ( Z - dir )
zcgcor SMx / Pv
5.634
Eccentricity along Z Dir from CG of Raft ez
1.809 >
ex l/6
57
1.275
zcgcor-l/2
1.809
7.1.2 Transverse direction ( X - dir )
CG from bottom edge
xcgcor SMz / Pv
1.118
Eccentricity along X Dir from CG of Raft
ex
ycgcor-b/2
0.118
ex
0.118 <
ez / l
0.237 m
ex / b 0.059 m Mx = Pv * ez =608.8*1.81
=
1101.52 kNm
=
71.97 kNm
Mz =Pv * ex =608.8*0.12
fmax
Pv/A + 6*Mx/(b*l^2) + 6*Mz/(l*b^2)
=
608.8/15.3+6*1101.52/(2*7.65^2)+6*71.97/(7.65*2^2)
fmax
110.37 kN/m2 <
fmin
608.8/15.3-6*1101.52/(2*7.65^2)-6*71.97/(7.65*2^2)
fmin
-30.79 kN/m2
Gross SBC
LOC
126
21.811 %
Redistributed Pressure
ez / l
=
0.237
ex / b =
0.059
From Tengs Chart
Coeff (K) =
58
3.027
Safe
b/6
0.333
Max P=
KQ/BL
=3.02694942934839 X 608.804 / 7.65 X 2
=
120.4456811
OK
Design Pressure
Along Z - Direction fzmax =Pv/A*(1+6*ABS(ez/l)) fzmax 100.678
=608.8/15.3x(1+6x0.237)
kN/m2
220.7401143
fzmin =Pv/A*(1-6*ABS(ez/l)) fzmin 0.000 kN/m2
= 608.8/15.3x(1-6x0.237) -61.57566987
Along X - Direction fxmax =Pv/A*(1+6*ABS(ex/b))
=608.8/15.3x(1+6x0.059)
fxmax 53.90 kN/m2 fxmin =Pv/A*(1-6*ABS(ex/b))
=608.8/15.3x(1-6x0.059)
fxmin 25.68 kN/m2 7.1.3 Pressure Along Z - Direction
LHS
fzl
0.00
kN/m2
RHS
fzr
100.68 kN/m2
Pressure Along X - Direction Top
fxt
53.90 kN/m2
Bottom
fxb
25.68 kN/m2
59
Check For Overturning
R.M
O.M
3262.43
Mx
167.7689
Mx
608.804
Mz
71.9732
Mz
Along X
19.45 Ok
Along Z
8.46
Ok
Check For Sliding
Restoring Force=
243.5216
KN
Sliding Force 55.364 Along X
4.398555018 Ok
129.053Along Z
1.886989067 Ok
60
7.1.4 Load calculations for combined Footing “F1”
=
Length of the footing
7650
mm
Breadth of the footing
b=
2000
mm
Depth of the footing
D=
350
mm
Pressure from analysis qmax =
110.37 kN/m²
qmin = -30.79 kN/m²
Uniformly distributed load Self wt. of Fdn.
2.0 x 0.35 x 25 =
17.500 kN/m
Wt. of soil filling
=
23.20 kN/m
Total
=
40.699 kN/m
61
Total downward force 40.699 x 7.7 + 0.00 + 0.00
311.345
Max B.M=
160
kNm
152.817
Max S.F=
180
kN
174.061
kN
SF
Design of Footing - X Direction
( Designed as cantilever)
62
Basic Data: Concrete grade
M30
fck =
30
N/mm²
Steel grade
Fe415 fy =
415
N/mm²
Load factor
ld=
Projection of footing from col. face l =
1000
mm
Breadth of the footing
b=
1000
mm
Depth of the footing
D=
350
mm
Clear cover to reinf.
d' =
75
mm
Dia of bar used
f=
12
mm
1.5
Section Data:
Load data: Maximum pressure
fmax= 53.90 kN/m2
Maximum Bending Moment
M=
26.95 kN-m
Total moment
M=
26.95 kN-m
Reinforcement: Factored Bending Moment
Mu = 40.43 kN-m
Eff. depth of footing
d =350 - 75 - 12/2 = 269mm
Mu/bd² = 40.43x 10^6/(1000 x 269²) =
0.559
% of Reinforcement required
ptr =
Minimum % of steel required
pmin = 0.13
\
Area of steel required Required spacing
pt =
0.16
0.16 Ast = 425.6 mm²/m 12mm dia bars @ 266 mm c/c
63
Provide
12mm dia bars @ 200
Provided Area of steel
mm c/c Astp = 565.5 mm²/m
7.1.5 Design of Strap Beam
Dimensions B=
600
mm
D=
750
mm
fck=
30
N/mm2
fy=
415
N/mm2
Maximum Bending moment KN-M
=
160.00
Factored Bending Moment, Mu KN-M
=
240.00
Effective depth of footing, d
=
665.00
Shear Force V KN
=
180.00
Factored Shear Force, Fu KN
=
270.00
Mu/bd2, R
=
0.90
=
0.25
Min .% of reinforcement required
=
0.20
Cover
=
75.00
Dia of bar
=
20.00
Area of cross section of bar
=
314.29
Area of steel required ,As
=
999.67
Provide number of bar dia required
=
4.18
Hence, number of dia of bar provided
=
6
Area of steel provided, As
=
1885.71
% of reinforcement required (Refer BS8110-3 1985 Chart no 9 : pg 17)
64
0.47
7.1.6 Check For Shear
Factored Shear Force, Fu KN
= 270.00
Nominal shear stress, tv N/mm2
= 0.68
B
= 7.370365484
Allowable Shear Stress
= 0.4852 N/mm2
Provide shear reinforcement Vu -
= 76.42
2
= 200.00
LeggedProvide 10mm bar at
Provide
10
mm
@
200.00 mm c/c
65
7.2 Design of Combined Foundation "F2"
Load Case
LC 22
Net SBC
SBCnet
Factor for inc in BC
Fbc
1
Joint No
9
11
106.25 kN/m2
PEDESTAL MARK
Col Mark
SUM 1
Z
wrt 1 0
4.2
X
wrt 1 0
0
2
P (kN)
-30.26 295.35
Mx (kNm)
0
Hz (kN)
-96.994 48.41 -48.59
Mz (kNm)
0
Hx (kN)
-55.795 -27.55 -28.25
0.00
0.00
0.00
0.00
Pedestal Size lZ
0.6
0.6
lX
0.775 0.775
Pped
16.86 16.86
Depth of foundation from the level of point of application of forces dforce
1.8
1.8
Depth of foundation below ground level (FGL) Depth of foundation below Natural Ground Level (NGL) Unit Weight of soil
66
Projections of Footing (from centreline of column) LHS
Cz1
0.9
RHS
Cz2
0.9
Bottom
Cx1
1.25
Top
Cx2
1.25
Length of footing
l
6.000 m
Width of footing
b
2.500 m
Depth of footing
d
0.350 m
Calculations :
Col Mark
SUM 1
2
xcor
0.9
5.1
ycor
1.25
1.25
Axial Load including weight of Pedestal Pconc 299
-13.41 312.21
Moment at base of foundation due to Horizontal Forces Mxh
-174.5892
-87.1344
-87.4548
Mzh
-100.43
-49.581
-50.85
Moments due to Conc. Moments& Horizontal Forces(Myc = My + Myh ) (Mxc = Mx + Mxh ) Mxc
-175
-87.1344
-87.4548
Mzc
-100
-49.581
-50.85
Gross SBC
SBCg= Fbc * SBCnet + gs * dfngl=
67
134.75 kN/m2 135
kN/m2
Total Axial Load incl wt of pedestal ( ∑Pconc )
∑P
Area of foundation ( Provided )
A
298.8005 kN l*b
Load due to soil
Psoil gs*(df - d)*(A -
Weight of foundation
Fbase A*d*25
Total Vertical Load
Pv
15
∑(lx*ly))
m2 307.43 kN 131.25 kN
∑P + Psoil + Fbase
737.48 kN
CG of load system from bottom left corner of footing Moments due to Pconc
∑ (Pconc Xcor)
External Moments
∑Mxm
∑Mzm ∑Mxh
Moment due to Horizontal Forces Moment due to Soil & Raft
1580.1909 ∑(Pconc Zcor) 373.500625 0
174.5892 ∑Mzh
∑ (Psoil+Fbase)*l/2 1316.04(Psoil+Fbase)*b/2
-100.43 548.349375 0
Total Moment
∑Mx 3070.82
∑Mz
821.419
Horizontal Forces
∑Hz -96.994
∑Hx
-55.795
Horizontal Forces
∑Hz -96.994
∑Hx
-55.795
Horizontal Forces
∑Hz -96.994
∑Hx
-55.79
Horizontal Forces
∑Hz -96.994
∑Hx
-55.795
7.2.1 Longitudinal direction ( Z - dir )
zcgcor
SMx / Pv
Eccentricity along Z Dir from CG of Raft ez
4.164 ex 1.164
68
zcgcor-l/2 > l/6
1.000
7.2.2 Transverse direction ( X - dir )
CG from bottom edge
xcgcor
∑Mz / Pv
1.114
Eccentricity along X Dir from CG of Raft
ex
ycgcor-b/2
0.136
ex ez / l
0.136 <
b/6
0.417
0.194 m
ex / b 0.054 m Mx = Pv * ez =737.48*1.16
=
858.38 kNm
=
100.43 kNm
Mz =Pv * ex =737.48*0.14
fmax
Pv/A + 6*Mx/(b*l^2) + 6*Mz/(l*b^2)
=
737.48/15+6*858.38/(2.5*6^2)+6*100.43/(6*2.5^2)
fmax
122.46 kN/m2 <
fmin
737.48/15-6*858.38/(2.5*6^2)-6*100.43/(6*2.5^2)
fmin
-24.13 kN/m2
Gross SBC
LOC
135
Safe
16.460 %
Redistributed Pressure
ez / l
=
0.194
ex / b =
0.054
From Tengs Chart
Coeff (K= 69
2.56794252
2.5767
Max P=
KQ/BL
= 2.56794251983484 X 737.48 / 6 X = 126.25375
OK
Design Pressure
Along Z - Direction fzmax =Pv/A*(1+6*ABS(ez/l))
=737.5/15x(1+6x0.194)
fzmax 107.110
244.9190667
kN/m2
fzmin =Pv/A*(1-6*ABS(ez/l)) -48.25773333
=737.5/15x(1-6x0.194)
fzmin 0.000 kN/m2 Along X - Direction fxmax =Pv/A*(1+6*ABS(ex/b))
=737.5/15x(1+6x0.054)
fxmax 65.23 kN/m2 fxmin =Pv/A*(1-6*ABS(ex/b))
=737.5/15x(1-6x0.054)
fxmin 33.10 kN/m2
7.2.3 Pressure Along Z - Direction
LHS
fzl
0.00
kN/m2
RHS
fzr
107.11 kN/m2
Pressure Along X - Direction Top Bottom
fxt
33.10 kN/m2 fxb
65.23 kN/m2
70
Check For Overturning
R.M
O.M
2896.23
Mx
174.5892
Mx
921.85
Mz
100.431
Mz
Along X
16.59 Ok
Along Z
9.18
Ok
Check For Sliding
Restoring Force=
294.992
KN
Sliding Force 55.795 Along X
5.287068734 Ok
96.994 Along Z
3.041342763 Ok
Load calculations for combined Footing Length of the footing
l=
6000
mm
Breadth of the footing
b=
2500
mm
Depth of the footing
D=
350
mm
Pressure from analysis qmax =
122.46 kN/m²
qmin = -24.13 kN/m²
71
7.2.4 Load calculations for combined Footing “F2”
Uniformly distributed load Self wt. of Fdn.
2.5 x 0.35 x 25 =
Wt. of soil filling Total
21.875 kN/m
51.24 kN/m 73.113 kN/m 73.113 kN/m
Total downward force 73.113 x 6.0 + 0.00 + 0.00
438.680
BM
72
kN
Max B.M=
130
kNm
126.595
Max S.F=
150
kN
149.884
SF
Design of Footing - Z Direction
( Designed as cantilever)
Basic Data: Concrete grade
M30
Steel grade
Fe415
fck =
Load factor
30
N/mm²
fy =
415
N/mm²
ld=
1.5
Section Data: Projection of footing from col. face
l=
1250
mm
Breadth of the footing
b=
1000
mm
Depth of the footing
D=
350
mm
Clear cover to reinf.
d'=
75
mm
Dia of bar used
f=
12
mm
73
Load data: Maximum pressure
fmax=
65.23 kN/m2
Maximum Bending Moment
M=
50.96 kN-m
Total moment
M=
50.96 kN-m
Reinforcement: Factored Bending Moment
Mu = 76.45 kN-m
Eff. depth of footing d =350 - 75 - 12/2 =269mm Mu/bd² = 76.45x 10^6/(1000 x 269²) =1.056 % of Reinforcement required
ptr
Minimum % of steel required
pmin = 0.13
\
Area of steel required Required spacing Provide
= 0.31
pt = 0.31 Ast = 821.8 mm²/m
12mm dia bars @ 138 mm c/c
12mm dia bars @125 mm c/c
Provided Area of steel
0
126.25375
2.5
8.01
Astp = 904.8 mm²/m
85.45932963 98.18245899 74
Moment
=41.90260613-11.38176563 =41.90260613 -11.38176563
=30.52084051
M/bd2
=0.632678663
Pt
=
0.18
Ast
=
821.8482124
Spacing
=
137.5436465
Shear
0.31
Soil
Vu=
66.60144501 18.1611
Tv=
0.270113448
B=
11.40125568
Tc=
0.40274325
48.44034501
OK
7.2.5 Design of Strap Beam
Dimensions B=
600
mm
D=
750
mm
Fck=
30
N/mm2
fy=
415
N/mm2
Maximum Bending moment KN-M
=
130.00
Factored Bending Moment, Mu KN-M
=
195.00
Effective depth of footing, d
=
665.00
Shear Force V KN
=
150.00
Factored Shear Force, Fu KN
=
225.00
Mu/bd2, Mu/bd2, R
=
0.73
Min .%of reinforcement required
=
0.20
Cover
=
75.00
% of reinforcement required= 0.20
75
Dia of bar
=
20.00
Area of cross section of bar
=
314.29
Area of steel required ,As
=
812.22
Provide number of bar dia required
=
3.58
Hence, number of dia of bar provided
=
6
Area of steel provided, As
=
1885.71
0.47
7.2.6 Check For Shear
Factored Shear Force, Fu KN
=
225.00
Nominal shear stress, tv N/mm2
=
0.56
=
7.370365484
=
0.4852 N/mm2
Provide shear reinforcement Vu -
=
31.42
2 Legged Provide 10mm bar at
=
200.00
B Allowable Shear Stress
Provide
10
mm
@
200.00 mm c/c
76
CHAPTER – 8 CONCLUSION Pipe racks or pipe supports are considered as one of the most important parts in a refinery which need to be constructed with precision. As supports of refinery pipes, such elements are installed numerously, to carry pipes with different size and diameters. The accessories increase the cost of the concrete pipe rack, therefore it shall be reduced to minimum. It is obvious that the use of anchoring rail will make it easy to fix apparatus or secondary frame. In majority of refineries, pipe rack systems are made of steel, and thus from the construction point of view, it is considered a simple job with no difficulty. Overall pipe rack design must meet the current needs of a client as well as any expansion plans without making major modifications to existing facilities. Available space in the pipe rack must be considered valuable and used to the utmost advantage of present and future needs.
77
