Project Report On EXECUTION OF A COMMERCIAL COMPLEX A Dissertation submitted in partial fulfillment of the requirement for the award of degree of Bachelor of Technology In
CIVIL ENGINEERING By
T.SANDEEP KUMAR REDDY
(09241A01A0)
BH. KARTHIKEYA VARMA
(09241A0172)
NEEHAR THUMMALURU
(09241A0183)
SHYAM GOEL
(09241A01A4)
DEPARTMENT OF CIVIL ENGINEERING GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING AND TECHNOLOGY (AFFILIATED TO JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY) NIZAMPET ROAD, HYDERABAD-500090
GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING AND TECHNOLOGY (AFFILIATED TO JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY)
DEPARTMENT OF CIVIL ENGINEERING CERTIFICATE
This is to certify that the project report entitled “ EXECUTION OF A COMMERCIAL COMPLEX” being submitted by T.SANDEEP KUMAR REDDY
(09241A01A0)
BH. KARTHIKEYA VARMA
(09241A0172)
NEEHAR THUMMALURU
(09241A0183)
SHYAM GOEL
(09241A01A4)
in partial fulfillment for the award of the Degree of Bachelor of Technology to the Jawaharlal Nehru Technological University. This record is a bonafide work carried out by him under my guidance and supervision. The results embodied in this project report have not been submitted to any other University or Institute for the award of any Degree or Diploma
HEAD OF THE DEPARTMENT
EXTERNAL GUIDE
DECLARATION: We hereby declare that the work presented in this project titled “Execution of commercial complex” submitted towards completion of mini-project in sixth Semester of B.Tech (CIVIL ENGINEERING) at the Gokaraju Rangaraju Institute of Engineering and Technology affiliated to Jawaharlal Nehru Technological University, Hyderabad is Hyderabad is authenticate work and had not been submitted to any University or Institute for any award.
T.SANDEEP KUMAR REDDY BH. KARTHIKEYA VARMA NEEHAR THUMMALURU SHYAM GOEL
(09241A01A0) (09241A0172) (09241A0183) (09241A01A4)
ACKNOWLEDGMENT We are fortunate enough to have an opportunity to present a project report for the Execution of a Commercial Complex. This project is very good example of team work and is an outcome of rigorous and painstaking effort of all the group members, without which one cannot imagine to materialize the dream of perpetuating such a tremendous task which not only adds valuable information to our knowledge but also increases our experience in field of building construction. We would
like to express our gratitude to all the people behind the screens who helped us in this project work. We profoundly
thank Dr. G. VENKATA RAMANA, professor, Head of the Department of Civil Engineering who has been an excellent guide and also a great source of inspiration, which has been very much valuable to us. We would like to take this opportunity to thank our guide for all that he had done in making our work grand success. His unstinting help was great asset to our project and without it we would not have accomplished what we have done now. The satisfaction and euphoria that accompany the successful completion of the task would be great but incomplete without the mention of the people who made it possible with their constant guidance and encouragement crowns all the efforts with success. In this context, I would like to thank all the other staff members, both teaching and non-teaching, who have extended their timely help and eased my task.
T. SANDEEP KUMAR REDDY
(09241A01A0)
BH. KARTHIKEYA VARMA
(09241A0172)
NEEHAR THUMMALURU
(09241A0183)
SHYAM GOEL
(09241A01A4)
ABSTRACT
EXECUTION OF A COMMERCIAL COMPLEX: In the modern industrialized world, construction usually involves the translation of designs into reality. In the field of civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking. Normally, the job is managed by a project manager, and supervised by a construction manager, design engineer, construction engineer or project architect. For the successful execution of a project, effective planning is essential. Involved with the design and execution of the infrastructure in question must consider the environmental impact of the job, the successful scheduling, budgeting, construction site safety, availability of building materials, logistics, inconvenience to the pub lic caused by construction delays and bidding, etc.. Our project involves construction of two five star hotels: - “The Oberoi” – A World Class Five Star Super Deluxe Luxury Business Hotel and “Trident” – A World Class Five Star Deluxe Business Hotels. This project started in October 2007 with a budget estimation of 121 crores for structure. Client for this project is Golden Jubilee Hotel Limited. And co ntractor is Nagarjuna Construction Company. When the project initiated in October 2007 the entire site was full of rock and boulders. Excavation work is carried out and entire rock strata are removed from the site. The very specialty of this project is the slabs are Post tension slabs in which slab of concrete is being prestressed using a specific method to increase the strength of the concrete and it is a high rise building with a Transfer floor of 1.5m thick at G+ 7 floor. Our study in this construction site includes several aspects such as Shuttering and types of shuttering, Reinforcement of steel, Concreting, vibrating, Curing and Water proofing, rectification of Concrete, Case studies and also study of d ifferent safety precautions undertaken at the site for the safety of labor and staff.
CONTENTS
S. No:
Topic
Page no.
1. CHAPTER-1
1.1 INTRODUCTION
2
1.2 PROJECT DESCRIPTION
3
1.3 SITE DESCRIPTION
4
2. CHAPTER-2
2.1 LITERATURE SURVEY
6
3. CHAPTER-3
3.1 EARTH WORK
12
3.2 PREPARATION FOR EARTH WORK
14
3.3 HAZARDS ASSOSIATED WITH EARTH WORK
16
4. CHAPTER-4
4.1 FOUNDATION
18
4.2 TYPES OF FOUNDATION
18
4.3 FOOTINGS
19
5. CHAPTER-5
5.1 SCAFFOLDING
24
5.2 TYPES OF SCAFFOLDING
25
5.3 ERECTION, ALTERATION AND DISMANTLING
28
6. CHAPTER-6
6.1 FORM WORK
30
6.2 TYPES OF FORM WORK
31
7. CHAPTER-7
7.1 REINFORCING STEEL
34
7.2 CHEMICAL COMPOSITION
37
7.3 NOMINAL SIZES
37
7.4 NOMINAL CROSS SECTION AREA AND MASS
38
7.5 BAR BENDING SCHEDULE
40
8. CHAPTER-8
8.1 CASE STUDY-I
43
8.2 CASE STUDY-2
52
9. CHAPTER-9
9.1 REFERENCES
54
10. List of Tables
Table 7.1 Chemical composition of Steel
37
Table 7.2 Nominal Cross Sectional Area and Mass
38
Table 7.3 Mechanical properties of High strength Deformed Bars 11. List of figures
39
Fig 1.1 View of Hotels after completion
2
Fig 1.2 Area and room Details
3
Fig 1.3 Aerial view of site before the start of construction in 2007
4
Fig 3.1 Shows Excavation of Rock strata at the site
12
Fig 3.2 Excavation carried out at the site
13
Fig 3.3 Aerial view of site conditions before excavation
15
Fig 3.4 Aerial view of site conditions after partial excavation
15
Fig 4.1 Aerial view of Construction of footings at site
20
Fig 4.2 Showing types of Footings
21
Fig 4.3 Showing Grade Bean Footing
22
Fig 5.1 Showing scaffolding at site
24
Fig 5.2 Independent Scaffold
25
Fig 5.3 Putlog Scaffold
25
Fig 5.4 Unit Frame Type Scaffold
26
Fig 5.5 Showing Scaffolding work at site
27
Fig 6.1 Form work at site
30
Fig 7.1 Reinforcement work being carried out at the construction site
34
Fig 7.2 Bar bending of Steel
41
Fig 8.1 Leakage of water necessitating Waterproofing
45
Fig 8.2 Green Seal flexi 201
47
Fig 8.3 Green Seal Flexi Liquid used for water proofing
48
Fig 8.4 Vandex BB 75
50
Fig 8.5 POLYDEK
51
Fig 8.6 Improper compacting necessitating Rectification work
53
CHAPTER-1 INTRODUCTION
1
1.1 INTRODUCTION
Our main aim involves in studying the execution work of a commercial complex consisting of two five star hotels The Oberoi and Trident in total area of 1.3 million square feet with a transfer floor of 1.5m thickness at G+7 level and having parking capacity of up to 800 cars.
Fig 1.1 View of Hotels after completion.
2
1.2 Project Description: The development site has excellent frontage on the road leading into the Hyderabad Information Technology and Engineering Consultancy (HITEC) city area. It is also about 3 kilometers from the Hyderabad International Trade Expositions Limited (HITEX) and Hyderabad International Convention Centre (HICC). Since the site is located near the entrance point to HITEC city nearby “Cyber Tower” & “Cyber Gateway”, it has an excellent vantage point in terms of office and IT complexes in the HITEC area and also in relation to the HITEX & HICC infrastructure. Hotels to be co-branded as “The Oberoi” – A World Class Five Star Super Deluxe Luxury Business Hotel and “Trident” – A World Class Five Star Deluxe Business Hotels. The hotels are so oriented that the guests are able to experience the natural marvel of “Bears Nose” and abutting greens of “Shilparamam” – a crafts village, spread over 60 acres. Land Allotted by Youth Advancement, Tourism and Culture (PMU) Department, (“YAT&C (PMU) D”) Government of Andhra Pradesh u nder Public Private Partnership (PPP) mode on Built, Operate and Transfer (BOT) basis. The Overall Build Up area For the Project is 1.3 million Sq. feet containing 545 total rooms.
Area & Rooms Details - Trident & Oberoi:
Fig 1.2 Area and room Details
3
1.3 SITE DESCRIPTION: Construction site is about 3 kilometers from the Hyderabad International Trade Expositions Limited (HITEX) and Hyderabad International Convention Centre (HICC). Since the site is located near the entrance point to HITEC city nearby “Cyber Tower” & “Cyber Gateway”, it has an excellent vantage point in terms of office and IT complexes in the HITEC area and also in relation to the HITEX & HICC infrastructure. Before the start of construction, the site is of large boulders of rock, which is excavated to a depth of 13 feet from the road level.
Fig 1.3 The above picture shows the aerial view of site before the start of co nstruction in 2007.
Excavation is carried out at the site and the entire rock boulders and rock strata are removed from the site to make it even. After excavation the entire area is leveled and plain concrete is poured to attain equal level of floor and is covered with a water proofing mat.
4
CHAPTER-2 LITERATURE SURVEY
5
2.1 LITERATURE SURVEY: CONSTRUCTION OF A STRUCTURE:
Construction of any structure involves following steps: •
Planning
•
Execution
•
Quality control
•
Safety
•
Store
•
Accounts
By following all the above steps one can achieve perfection in any construction process right from the beginning of the project to till the end of it.
2.1.1 PLANNING: Construction planning is a fundamental and challenging activity in the management and execution of construction projects. It involves the choice of technology, the definition of work tasks, the estimation of the required resources a nd durations for individual tasks, and the identification of any interactions among the different work tasks. A good construction plan is the basis for developing the budget and the schedule for work. Developing the construction plan is a critical task in the management of construction, even if the plan is not written or otherwise formally recorded. In addition to these techn ical aspects of construction planning, it may also be necessary to make organizational decisions about the relationships between project participants and even which organizations to include in a project. For example, the extent to which sub-contractors will be u sed on a project is often determined during construction planning. Planning for construction projects involves the logical analysis of a project, its requirements, and the plan (or plans) for its execution. This will also include consideration of the existing constraints and available resources that will affect the exec ution of the project. Considerable planning is required for the support functions for a project, material storage, worker facilities, office space, temporary utilities, and so on. Planning, with respect to the critical path method, involves the identification of the activities for a project, the ordering of these activities with respect to each other, and the development of a network logic diagram that graphically portrays the activity planning. In developing a construction plan, it is common to adopt a primary emphasis on either cost control or on schedule control. Some projects are primarily divided into expense 6
categories with associated costs. In these cases, construction planning is cost or expense oriented. Within the categories of expenditure, a distinction is made between costs incurred directly in the performance of an activity and indirectly for the accomplishment of the project. For example, borrowing expenses for project financing and overhead items are commonly treated as indirect costs. For other projects, scheduling of work activities over time is critical and is emphasized in the planning process. In this case, the planner insures that the proper precedents a mong activities are maintained and that efficient scheduling of the available resources prevails. Traditional scheduling procedures emphasize the maintenance of task precedents (resulting in critical path scheduling procedures) or efficient use of resources over time (resulting in job shop scheduling procedures). Finally, most complex projects require consideration of both, cost and scheduling over time, so that planning, monitoring and record keeping must consider both dimensions. In these cases, the integration of schedule and budget information is a major concern. 2.1.2 EXECUTION: Once the site engineer receives the drawings, the construction or execution of project starts initiated. Execution of the project involves in the entire construction i.e. from footings to the slabs. Execution of project involves following steps:
i)
•
Study of Drawings
•
Important points to be listed out.( Conditions )
•
Formwork
•
Reinforcement of Steel
•
Concreting
•
Brick work
Study of Drawings:
Drawings which contain measurements and reinforcement and schedules are sent to site engineer from planning department. Once the site engineer receives those drawings, construction is initiated after a detailed study of drawings by site engineer and project in charge. These drawings must be studied painstakingly since any mistake can cause a great effect to entire construction project. Required number of steel bars and their diameters are mentioned in these drawings including the schedule of construction process.
7
ii)
Points to be listed out:
The site engineer must note down important points such as room dimensions, length and breadth and height etc. and all necessary conditions made by the client for the execution of construction.
iii)
Formwork:
Formwork is an ancillary construction, used as a mould for a structure. Into this mould, fresh concrete is placed only to harden subsequently. The construction of formwork takes time and involves expenditure upto 20 to 25% of the cost of the structure or even more. Design of these temporary structures is made to economic expenditure. The operation of removing the formwork is known as stripping. Stripped formwork can be reused. Reusable forms are known as panel forms and non-usable are called stationary forms. Timber is the most common material used for formwork. The disadvantage with timber formwork is that it will warp, swell and shrink. Application of water impermeable cost to the surface of wood mitigates these defects.
Types of Formwork: •
Traditional Timber formwork
•
Engineered Formwork System
•
Re-usable plastic formwork
•
Permanent Insulated Formwork
•
Stay-In-Place structural formwork systems
.
iv)
Reinforcement of steel:
Reinforcing steel is a common steel bar, and is commonly used as a tensioning device in reinforced concrete and reinforced masonry structures holding the concrete in compression. It is usually formed from carbon steel, and is given ridges for better mechanical anchoring into the concrete. Steel has an expansion coefficient nearly equal to that of modern concrete. If this were not so, it would cause problems through additional longitudinal and perpendicular stresses at temperatures different than the temperature of the setting.
8
v)
Concreting
Concrete is a composite construction material composed primarily of aggregate, cement and water. There are many formulations that have varied properties. The aggregate is generally coarse gravel or crushed rocks such as limestone, or granite, along with a fine aggregate such as sand. The cement, commonly Portland cement, and other cementitious materials such as fly ash and slag cement, serve as a binder for the aggregate. Various chemical admixtures are also added to achieve varied properties. Water is then mixed with this dry composite which enables it to be shaped (typically poured) and then solidified and hardened into rock-hard strength through a chemical process known as hydration. The water reacts with the cement which bonds the other components together, eventually creating a robust stone-like material. Concrete has relatively high compressive strength, but much lower tensile strength. For this reason it is usually reinforced with materials that are strong in tension (often steel).
2.1.3 QUALITY CONTROL: Quality control and safety represent increasingly important concerns for project managers. Defects or failures in constructed facilities can result in very large costs. Even with minor defects, re-construction may be required and facility operations impaired. Increased costs and delays are the result. In the worst case, failures may cause personal injuries or fatalities. Accidents during the construction process can similarly result in personal injuries and large costs. Indirect costs of insurance, inspection and regulation are increasing rapidly due to these increased direct costs. Good project manage rs try to ensure that the job is done right the first time and that no major accidents occur on the project. As with cost control, the most important decisions regarding the quality of a completed facility are made during the design and planning stages rather than during construction. It is during these preliminary stages that component configurations, material specifications and functional performance are decided. Quality control during construction consists largely of insuring conformance to these original designs and planning decisions With the attention to conformance as the measure of quality during the construction process, the specification of quality requirements in the design and contract documentation becomes extremely important. Quality requirements should be clear and verifiable, so that all parties in the project can understand the requirements for conformance. Much of the discussion in this chapter relates to the development and the implications of different quality requirements for construction as well as the issues associated with insuring conformance.
9
2.1.4 SAFETY: Construction is the most dangerous land-based work sector and is a relatively hazardous undertaking. Construction has a number of characteristics making it inherently hazardous. Large forces are involved in many operations. The jobsite is continually changing as construction proceeds. Workers do not have fixed worksites and must move around a structure under construction. The tenure of a worker on a site is short, so the worker's familiarity and the employer-employee relationship are less settled than in manufacturing settings In contrast to most industrial accidents, innocent bystanders may also b e injured by construction accidents. Several crane collapses from high rise buildings under construction have resulted in fatalities to passersby. Prudent project managers a nd owners would like to reduce accidents, injuries and illnesses as much as possible. Educating workers and managers in proper procedures and hazards can have a direct impact on jobsite safety. The realization of the large costs involved in construction injuries and illnesses provides a considerable motivation for awareness and education. Regular safety inspections and safety meetings have become standard practices on most job sites.
2.1.5 STORE: Store is a place where the entire construction material is stored. Before the commencement of work, site engineer receives the drawings from planning department and the amount of material required is mentioned in d rawings. 2.1.6 ACCOUNTS: Accounts include the data of all material and money involved in the construction project. Records are maintained to keep track of time to time data.
10
CHAPTER-3 EARTH WORK
11
3.1 EARTH WORK: Earth work in construction is an operation in which earth, rock, or other material in or on the ground is moved or otherwise displaced by means of tools, equipment, or explosives, and includes earthwork, trenching, wall shafts, tunneling and underground work. High-risk obligations apply to excavations with a depth greater than 1.5 meters.
Fig 3.1 Shows Excavation of Rock strata at the site.
12
Fig 3.2 Excavation carried out at the site.
Excavation is regarded as one of the most hazardous construction operations. Excavation failure occurs very quickly, giving a worker virtually no time to escape, especially if the collapse is extensive and the excavation is a trench. Normally, a slab of earth collapses off the trench face under its own weight and breaks against the opposite wall of the excavation, burying and crushing any person in its path. This can result in death by suffocation or internal injuries.
13
3.2 PREPARATION FOR EARTH WORK: Prior to beginning excavation, grading, or embankment operations in any area, the following items are required to be completed:
1) Clearing and grubbing is conducted. This includes the removal of all perishable material such as tree roots, stumps, sod, weeds, agricultural debris, etc. 2) Check sections are taken and checked satisfactorily with those on the plans. On contracts with construction engineering, the Contractor is responsible for securing check sections. The method of checking che cking original cross sections is outlined in the General Instructions to Field Employees. 3) After the previous items have been completed, the Contractor proceeds with scalping in areas where excavations are to be made, or embankments are to be placed. Another common term for scalping is stripping. Scalping is the removal of the upper 4 in. of the soils. Removal is necessary to ensure that decayable vegetation is not incorporated into an embankment. Although 4 in. is the maximum depth, top soils containing large quantities of humus to a depth greater than 4 in. are removed until suitable materials are exposed. Scalping is completed to the limits the area where excavations are to be made or Embankments are to be placed. The grading operations are inspected closely for unsuitable material. Roots and other large perishable objects are removed and stockpiled outside of the construction limits for later disposal. 4) All pronounced depressions left in the original ground surface by removal of objectionable material from within embankment limits are filled with acceptable material and compacted to the density required for the embankment. The upper 6 in. of the original ground is compacted with a roller weighing no less than 10 t, or with other approved compacting equipment. 5) The final step before embankment placement is proof rolling. This work is done with a pneumatic tire roller. Other approved equipment, such as a fully loaded tri-axle dump truck, may be substituted for the pneumatic tire roller. When an unstable area is encountered, the engine labors to pull the roller through the spongy area. After proof rolling has been completed and all soft or unstable areas have been corrected, the area is ready for placement of the new embankment.
14
AERIAL VIEW OF SITE BEFORE AND AFTER EXCAVATION:
Fig 3.3 Showing aerial view of site conditions before excavation
Fig 3.4 Showing aerial view of site conditions after partial excavation
15
3.3 HAZARDS ASSOSIATED WITH EARTH WORK: Without careful planning and management, an excavation site can be hazardous to all persons in the vicinity of the construction work. Particular hazards identified in relation relation to excavation work include: • • • • • • • • • • • • •
the depth of the excavation nature of the strata (soil variations creating the potential for the sides to collapse) fractures or faults the presence of water (from other sources) exposure to wet weather any load close to the edge of the zoned of influence the exposure time any previous disturbance adjoining buildings adjacent excavations vibration which may increase the potential to collapse the presence of existing underground services chemical gases
RISKS ASSOSIATED WITH EARTH WORK: •
•
•
Excavation work is inherently dangerous and regarded as the most dangerous construction work. Excavation failures occur quickly and this limits the ability of the worker to escape especially if the collapse is extensive or is a trench. The speed of an excavation collapse increases the risk associated with this type of work and the consequences are significant as the falling earth can bury or crush any person in its path. This can result in death by suffocation or internal crush injuries.
The magnitude of the consequences particularly in relation to trench collapse highlights the need to protect the employees and other person working at or near excavation sites.
16
CHAPTER-4 FOUNDATION
17
4.1 FOUNDATION: A foundation is the lowest and supporting layer of a structure. Foundation is part of a building, usually below the ground, that transfers and distributes the weight of the building onto the ground such that the compressive stresses do not exceed the bearing capacity of the soil.
4.2 TYPES OF FOUNDATION: Foundations are generally divided into two categories: shallow foundations and deep foundations 1. Shallow foundations: Shallow foundations, often called footings, are usually embedded about a meter or so into soil. One common type is the spread footing which consists of strips or pads of concrete (or other materials) which extend below the frost line and transfer the weight from walls and columns to the soil or bedrock. Another common type of shallow foundation is the slab-on-grade foundation where the weight of the building is transferred to the soil through a concrete slab placed at the surface. Slab-on-grade foundations can be reinforced mat slabs, which range from 25 cm to several meters thick, depending on the size of the building, or posttensioned slabs, which are typically at least 20 cm for houses, and thicker for heavier structures. 2. Deep foundations: A deep foundation is used to transfer the load of a structure down through the upper weak layer of topsoil to the stronger layer of subsoil below. There are different types of deep footings including impact d riven piles, drilled shafts, caissons, helical piles, and earth stabilized columns. The naming conventions for different types of footings vary between different engineers. Historically, piles were wood, later steel, reinforced concrete, a nd pre-tensioned concrete.
18
4.2.1 DESIGN: Foundations are designed to have an adequate load capacity with limited settlement by a geotechnical engineer, and the footing itself is designed structurally by a structural engineer. The primary design concerns are settlement and bearing capacity. When considering settlement, total settlement and differential settlement is normally considered. Differential settlement is when one part of a foundation settles more than another part. This ca n cause problems to the structure the foundation is supporting. It is necessary that a foundation not be loaded beyond its bearing capacity or the foundation will "fail". Other design considerations include scour and frost heave. Scour is when flowing water removes supporting soil from around a footing (like a pier supporting a bridge over a river). Frost heave occurs when water in the ground freezes to form ice lenses. Changes in soil moisture can cause expansive clay to swell and shrink. This swelling can vary across the footing due to seasonal changes or the effects of vegetation removing moisture. The variation in swell can cause the soil to distort, cracking the structure over it. This is a particular problem for house footings in semi-arid climates such as South Australia, Southwestern US, Turkey, Israel, Iran and South Africa where wet winters are followed by hot dry summers. Raft slabs with inherent stiffness have been developed in Australia with capabilities to resist this movement. When structures are built in areas of permafrost, special consideration must be given to the thermal effect the structure will have on the permafrost. Generally, the structure is designed in a way that tries to prevent the permafrost from melting.
4.3 FOOTINGS:
CONSTRUCTION OF FOOTINGS: Construction of footings involves following steps: •
Reinforcement of Steel bars.
•
Shuttering on all sides( except bottom)
•
Placing cover blocks so as to prevent appearance of Skeleton
•
Concrete pouring.
•
Curing.
•
Providing starter for the erection of column.
19
Fig 4.1 Aerial view of Construction of footings at site. 4.3.1 TYPES OF FOOTINGS Footing requirements are generally covered in the building code and sized in accordance with the bearing capacity of the soil and the weight of the building. In areas subject to seasonal frost, the bottom of the footing must be placed below the frost line to prevent damage to the footing and structure due to frost heave.
Typical footing types include: • • •
spot footings continuous spread footing grade beam footing
20
Spot Footings:
A spot or pad footing is used to support a single point of contact, such as under a pier or post. A spot footing is typically a 2' by 2' square pad, 10" to 12" thick, and made with reinforced concrete rated to 3,000 to 5,000 pounds per square inch (psi) in compression.
Fig 4.2 Showing types of Footings
Continuous Spread Footing:
A continuous spread footing is commonly used to provide a stable base around the entire perimeter of a structure. Buildings with spread footings often include interior spot footings. A spread footing supports the weight (load) from the exterior or foundation walls. The footing thickness provides the strength needed to support the weight. The wider width of the footing base creates a large area to transfer this weight to the ground and to prevent settlement. The dimensions of a continuous spread footing vary according to the soil conditions under the building, the load placed on the footing, and the construction style of the structure being supported. It is common practice to make the footing thickness equal to the thickness of the foundation wall, and to provide a footing projection on each side of the foundation wall equal to one-half the foundation wall thickness. Spread footings are frequently 16" to 24" wide, 6" to 16" thick, and made with reinforced concrete rated to 2,000 to 5,000 psi in 21
compression. Table lists the minimum footing widths required for a range of allowable bearing capacities and building sizes.
Grade Beam Footing:
A grade beam footing is a continuous reinforced-concrete member used to support loads with minimal bending. Grade beams are capable of spanning across non-load bearing areas, and are commonly supported by soil or pilings. A continuous grade beam is frequently constructed by digging a trench at least 8" wide to the depth needed to span the distance between supports. Grade beam footings differ from continuous spread footings in how they distribute loads. The depth of a grade beam footing is designed to distribute loads to bearing points, while the width of a continuous spread footing is designed to transfer loads to the ground.
Fig 4.3 Showing Grade Bean Footing
22
CHAPTER-5 SCAFFOLDING
23
5.1 SCAFFOLDING: Scaffolding is defined as any structure, framework, swinging stage, suspended scaffolding, or boatswain’s chair, of a temporary nature, used or intended to be used for the support or protection of workers engaged in or in connection with construction work, for the purpose of carrying out that work or for the support of materials used in c onnection with any such work; and includes any scaffolding constructed as such and not dismantled, whether or not it is being used as scaffolding; and also includes any plank, coupling, fastening, fitting or device used in connection with the construction, erection, or use of scaffolding. Scaffolding process is defined as the planning for, the design of, the erection of, the inspection of, the use of, and the dismantling of any scaffolding. The scaffolding process does not include the erection of structures constructed using scaffolding components, such as false work, temporary grandstands, lighting towers, etc.
Fig 5.1 Showing scaffolding at site.
24
5.2 Types of Scaffolding (according to IS: 2750 – 1992): 1) Independent Scaffold : The scaffolding supports on two rows of uprights, independent of the structure under construction. It may be either ‘individual component type’ or ‘unit frame type’.
Fig 5.2 Independent Scaffold
2) Individual Component Type Scaffold: Independent or putlog scaffold consisting of an assembly of individual tubes and fittings. 3) Putlog Scaffold: This scaffolding is supported by a single row of up rights in combination with load bearing parts of the structure. It may be either ‘individual component type’ or ‘unit frame type’
Fig 5.3 Putlog Scaffold 25
4) Unit Frame Type Scaffold: Independent or putlog scaffold consisting of an assembly of prefabricated frames suitably connected or fitted and used in combination with or without tubes.
Fig 5.4 Unit Frame Type Scaffold
26
Fig 5.5 Showing Scaffolding work at site. 27
MATERIALS: Various standards prescribe scaffolding made of timber, steel tubes, aluminum tubes or prefabricated frames. Other materials, provided they a re suitable and adequate in strength, may be used subject to the approval of the Secretary of Labour. All scaffold materials must be in sound condition and be examined by a competent person before use.
5.3 ERECTION, ALTERATION AND DISMANTLING: All scaffolding, whether notifiable or not, must be erected, a ltered and dismantled by competent workers under proper supervision. Scaffolding must not be used unless the employer or employer’s representative on the work is satisfied that it is safe for use and complies with the regulations. Scaffolding must not be altered or interfered with except on the instructions of the employer or employer’s representative. Scaffolders must ensure that members of the public are not endangered while they are erecting, altering or dismantling scaffolds. They should also ensure that the lower working platforms are not used while the upper lifts are being worked on unless a fully decked platform, with screens if necessary, separates the part being erected or dismantled from the lower part in use.
28
CHAPTER-6 FORM WORK
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6.1 FORMWORK (SHUTTERING): Shuttering or form work is the term used for temporary timber, plywoo d, metal or other material used to provide suppo rt to wet concrete mix till it gets strength for selfsupport. It provides supports to horizontal, vertical and inclined surfaces or also provides support to cast concrete according to required shape and size. The form work also produces desired finish concrete surface. Shuttering or form work should be strong en ough to support the weight of wet concrete mix and the pressure for placing and compacting concrete inside or on the top of form work/shuttering. It should be rigid to prevent any deflection in surface after laying cement concrete and be also sufficient tight to prevent loss of water and mortar form cement conc rete. Shuttering should be easy in handling, erection at site and easy to remove when cement concrete is sufficient hard.
Fig 6.1 Form work at site.
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6.2 TYPES OF FORMWORK: Formwork comes in several types: 1. Traditional timber formwork: The formwork is built on site out of timber and plywood or moisture-resistant particleboard. It is easy to produce but time-consuming for larger structures, and the plywood facing has a relatively short lifespan. It is still used extensively where the labour costs are lower than the costs for procuring re-usable formwork. It is also the most flexible type of formwork, so ev en where other systems are in use, complicated sections may use it. 2. Engineered Formwork System: This formwork is built out of prefabricated modules with a metal frame (usually steel or aluminum) and covered on the application (concrete) side with material having the wanted surface structure (steel, aluminum, timber, etc.). The two major advantages of formwork systems, compared to traditional timber formwork, are speed of construction (modular systems pin, clip, or screw together quickly) and lower life-cycle costs (barring major force, the frame is almost indestructible, while the covering if made of wood; may have to be replaced after a few - or a few dozen - uses, but if the covering is made with steel or aluminum the form can achieve up to two thousand uses depending on care and the applications). 3. Re-usable plastic formwork: These interlocking and modular systems are used to build widely variable, but relatively simple, concrete structures. The panels are lightweight and very robust. They are especially suited for low-cost, mass housing schemes. 4. Permanent Insulated Formwork: This formwork is assembled on site, usually out of insulating concrete forms (ICF). The formwork stays in place after the concrete has cured, and may provide advantages in terms of speed, strength, superior thermal and acoustic insulation, space to run utilities within the EPS layer, and integrated furring strip for cladding finishes. 5. Stay-In-Place structural formwork systems: This formwork is assembled on site, usually out of prefabricated fiber-reinforced plastic forms. These are in the shape of hollow tubes, and are usually used for columns and piers. The formwork stays in place after the concrete has cured and acts as axial and shear reinforcement, as well as serving to confine the concrete and prevent against environmental effects, such as corrosion and freeze-thaw cycles. Recommended Period for Removal of Shuttering: • • • • •
48 hours for sides of foundations, columns, beams and walls. 7 days for underside of slab up to 4.5 meter span 14 days for underside of slab, beams, arches above 4.5 meter up to 6 meter span. 21 days for underside of beams arches above 6 meter span and up to 9 meter span. 28 days for underside of beams arches above 9 meter span.
Defects Found In Shuttering/Form Work • •
The supports of form work are not in plumb and are not cross braced. The ground supports of ballies are poor and therefore settle the form work. 31
•
• • • •
•
•
• •
• • •
There is insufficient thickness of shuttering plates/planks unable to bear la teral pressure imposed by wet concrete especially in columns. Shuttering plates are not cleaned and oiled or oiled with dirty oil. There are many insufficient and loose connections in centering and shuttering. The form work is removed before time. The work is not planned and designed properly. In case of beam shuttering proper provision for retaining side is not made. Hence the side of beam is not in proper line. The shuttering is poorly made with cracked and warped timber planks having lots of holes and knots. Through bolts for RCC walls form work for an underground tank is used. Later these holes made by bolts are not plugged. ‘Ballies’ are resting on bricks or brick pillars Ballies are not in one piece. Small ballies are used and these are not properly jointed. Also no additional cross bracing is provided at the joint. The supports under shuttering plates are not properly tight. The earth work under supports is not properly compacted before starting shuttering work. The bottom of ‘ballies’ are in wedge shape, not having proper base.
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CHAPTER-7 STEEL REINFORCEMENT
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7.1 REINFORCING STEEL: A reinforcing bar also known as reinforcing steel, reinforcement steel, rerod, a deformed bar, reo, or reo bar, is a common steel bar, and is commonly used as a tensioning device in reinforced concrete and reinforced masonry structures holding the concrete in compression. It is usually formed from carbon steel, and is given ridges for better mechanical anchoring into the concrete. .
Fig 7.1 Showing the reinforcement work being carried out at the construction site.
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Use in Concrete: Concrete is a material that is very strong in compression, but relatively weak in tension. To compensate for this imbalance in concrete's behavior, rebar is cast into it to carry the tensile loads. For this purpose, the steel reinforcement of a concrete structure is, conceptually, divided in two types of reinforcement: primary reinforcement and secondary reinforcement. Primary reinforcement refers to the reinforcement steel which is employed specifically to guarantee the necessary resistance needed by the structure to support the design loads. Secondary reinforcement, also known as distribution reinforcement, is employed for durability and aesthetics reasons, by providing enough localized resistance to limit cracking and resist stresses caused by effects such as temperature changes and shrinkage. It is also employed to confer resistance to concentrated loads by providing enough localized resistance and stiffness for a load to spread through a wider area.
Different aspects of reinforcement placement: The important aspects of reinforcement placement are:•
Concrete Cover
•
Lap Length
•
Development Length
•
Bar spacing and Bar size
1) Concrete Cover: Cover less than the design cover: The life of the reinforcing steel can be shortened due to corrosion from increased exposure to deicing materials and/or the elements. Corrosion of the reinforcing steel will cause an increase in the diameter of the steel, which will cause the concrete outside the steel to sometimes spall off and the concrete around the reinforcing steel to become debonded from the reinforcing steel. This debonding of the concrete from the reinforcing steel can reduce the strength of the structure by preventing the necessary interaction between the concrete and the reinforcing steel. Cover more than the design cover: will reduce the strength of the structure. Placing the reinforcing steel with more than the design co ver causes the neutral axis to be shifted higher in the section, which reduces the area of concrete that is in compression and increases the cracked area of concrete in tension. This decrease in useful concrete (over Neutral Axis) and increase in useless concrete (below Neutral Axis) greatly reduces the strength of the structure.
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2) Lap Length: It would be ideal to make reinforcing bars in structural members (like slabs, columns, beams etc.) one continuous bar, this however would be impractical due to difficulties in transporting and handling the steel. In order to achieve the same effect as having one continuous bar, shorter bars with minimum (over) lap lengths are used. The design lap length is usually a minimum length required to transfer stress from one bar to another. If the actual lap length is less than the required lap length, the stress may not be transferred to the other bar, which could cause a failure in the structure at that lap location. 3) Development Length: The development length is often shown on the plans as a minimum embedment length. The purpose of the development length is to anchor the reinforcing bars beyond the area where the strength of the bars is needed. Without the required development length, the reinforcing bar would pull out of the concrete surrounding it and the structure could fail. 4) Bar Spacing and Bar Size: Both the spacing and the size of the reinforcing bars control the amount of steel in the tension area. The amount of reinforcing steel in the tension area of the structure has a large impact on the strength of the structure.
MANUFACTURE (IS 1786-2008): Steel shall be manufactured by the open-hearth, electric, duplex, basic-oxygen process or a combination of these processes. In case any other process is employed by the manufacturer, prior approval of the purchaser should be obtained. The bars/wires shall be manufactured from properly identified heats of mould cast, continuously cast steel or rolled semis. The steel bar/wires for concrete reinforcement shall be manufactured by the process of hot rolling. It may be followed by a suitable method of cold working and/or in-line controlled cooling.
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7.2 CHEMICAL COMPOSTION (IS 1786-2008):
Table 7.1 Chemical composition of Steel
7.3 NOMINAL SIZES (IS 1786-2008): The nominal sizes of bars/wires shall be as follows: 4 mm. 5 mm 6 mm 10 mm 12 mm 16 mm 20 mm 25 mm 28 mm 32 mm 36 mm 40 mm • • • • • • • • • • • •
Effective Cross-Sectional Area and Mass of Deformed Bars and Wires: •
Mass of Deformed Bars is calculated from the formula: Unit weight of steel (w) =2 ÷ 162; where‘d’ is diameter of Steel Bar.
•
For bars/wires whose pattern of deformation is such that by visual inspection, the cross-sectional area is substantially uniform along the length of the bar/wire, the
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effective cross-sectional area shall be the gross sectional area determined a s follows, using a bar/wire not less than 0.5 m in length: Gross cross-sectional area, in2 = ÷ 0.00785; where L= Length measured to a precision of ±0.5%,
7.4 NOMINAL CROSS-SECTIONAL AREA AND MASS (IS1786-2008):
Table 7.2 Nominal Cross Sectional Area and Mass
Depending on the loading conditions appropriate steel size is selected giving due consideration to Mass and Cross section Area per 2
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Mechanical Properties of High Strength Deformed Bars and Wires (IS 1786-2008):
Table 7.3 Mechanical properties of High strength Deformed Bars an d Wires
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7.5 BAR BENDING SHEDULE: Bar bending schedule or bar scheme diagram is used to communicate the design requirement of reinforcement steel to the fabricator and ex ecution team and to enumerate the weight of each size of steel. It is a list of reinforcement steel bars, which includes size and number of bars, cutting length of bars, weight of steel and a sketch representing the shape of bar to be bent. Generally, civil engineers who are familiar in RCC structure are employed to prepare Rebar bending schedule. When compared to common quantity take offs, preparation of Rebar schedule needs excessive time for calculation. These calculations include cutting length, deduction of bend allowance within cutting length and summary of weight of each size separately. Insertion of any omitted items or revisions in the drawing may lead to repeated calculations and consume ample time.
Fig 7.2 Bar bending of Steel.
A thorough structural analysis must be done before making a bar bend schedule for safety purposes. Bar bending schedule will aide as in determining the materials quantity, strength and for economic and practical purposes as well. Structural members such as beams, girders, columns, footings, piles are usually done with bar bend schedule as a guide in 40
positioning them upon casting in place. Some examples are the proper bending of ties and stirrups, bending of hooks, point where the top and bottom bars terminate, bend for anchorages, bend for development, bend for splicing if necessary, U straps, bend of bars in slabs, and bend for longitudinal position of rebar.
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CHAPTER-8 CASE STUDIES
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8.1 CASE STUDY: I
8.1.1 Water Proofing: In building construction, a structure needs waterproofing since concrete itself will not be watertight on its own (but note concrete is easily waterproofed with additives). The conventional system of waterproofing involves 'membranes'. This relies on the application of one or more layers of membrane (available in various materials: e.g., bitumen, silicate, PVC, EPDM etc.) that act as a barrier between the water and the building structure, preventing the passage of water. However, the membrane system relies on exacting application, presenting difficulties. Problems with application or adherence to the substrate can lead to leakage. This dampness or moisture can prove very damaging to any construction. A lot of money can get wasted due to unexpected seepage of water into walls or woodwork. Sometimes the presence of moisture can even corrode the steel framework, thus placing the whole structure at risk. In order to safeguard precious construction and also to avoid future inconvenience, it is highly important to take strict measures to waterproof. There are various waterproofing techniques that can be used during and after the construction of the house. The choice of method depends upon various factors, the primary one amongst them being cost.
Steps involved in water proofing are Surface Preparation Coating(chemical) • •
Surface Preparation Improperly prepared surfaces can result in reduced application integrity and service life. Up to 80% of all failures can be directly attributed to inadequate surface preparation, which affects treatment performance.
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Fig 8.1 Leakage of water necessitating Waterproofing.
Economics and surface contamination (including its effect on the substrate) will also influence the selection of surface preparation methods. The surface must be dry and in sound condition. Remove mildew, oil, dust and dirt, loose rust, peeling paint or other contamination to ensure proper treatment. No ex terior application should be done immediately after a rain, during foggy Weather, when rain is predicted, or when the temperature is below 10° C.
Coating Waterproofing coating is done by different chemicals like Green Seal Flexi, Polydeck, and Vandex. Number coatings are two, one vertical and the other horizontal with a time gap of 3-4 hours between different coatings followed by water testing for approximately two days depending upon the requirement.
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i) Green Seal Flexi 201 Greenseal Flexi 201 is a flexible cement based on a two component polymer modified waterproof coating. It is suitable to apply to concrete and mortar to prevent water infiltration and to fill and seal pores and voids, cracks and hair lines of all substrates and ye t provide a breathable coating which allows water vapour transmission. It is ideal as a protective layer against aggressive gas such as carbon dioxide and also frost and thawing salts. Greenseal Flexi 201 consists of Portland cement, selected and well graded sand and plasticizer, formulated with specially selected and graded fine quartz and high quality latex to create brushable, smooth slurry with excellent bonding and adhesion to most substrates. GS 201 is supplied in 2 components (GS 201 is packed in 33 kg set-Powder - 23 kg & Polymer liquid - 10 kg). To generate a consistent slurry, pour the liquid component into a pail and then gradually add the powder component to the liquid. While mixing, use a stirrer to stir the mixture until the mixture is free from lumps. Take note of the consistency of the slurry. The consistency of the slurry can be altered by reducing or adding in powder component. Apply GS 201 with a stiff brush or spray onto the prepared surface with at least two coats. The interval of each coat should be 1-2 hours minimum. To avoid pin holes and ensure full coverage, apply each brush coat in different directions. For large spaces, spray is recommended by using a worm-gear type of spray equipment. For best results, apply GS 201 under shaded shelter to prevent rapid drying of the coating.
Uses Greenseal Flexi 201 consists of Portland cement, selected and well graded sand and plasticizers, formulated with specially selected and graded fine quartz and high quality latex to create brush able, smooth slurry with excellent bond and adhesion to most substrates.
It is a flexible cementitious waterproof suitable used in: Bathrooms, toilet and kitchens Balconies and planter boxes Swimming pools Water tanks Basement wall Retaining walls Sea walls Reservoirs Concrete gutters. • • • • • • • • •
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Advantages 1) Minimum surface preparation 2) Applied directly to the concrete by brush or spray 3) Breathable - allows transmission of water vapour from interior of building 4. Good elongation 5. Can be applied on damp surfaces. 6. Excellent adhesion bonds to porous and non-porous surfaces 7. Toxic-free and flexible 8. Non-corrosive to steel and iron. 9. High resistance to carbon dioxide and chloride ion diffusion. No water or other material should be adding in the mixture.
Fig 8.2 Green Seal flexi 201
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Fig 8.3 Green Seal Flexi Liquid used for water proofing.
Application Instructions Surface Preparation •
•
•
•
Substrates to be applied with GS 201 must be clean and free from laitance, protrusions, loose particle, dirt, oil and grease. Sharp edges must be flattened and uneven surfaces must be leveled or repaired with a mortar screed by using GS300. Clean and proper repaired surface must be thoroughly saturated with water prior to application of GS Primer. Be caution: No standing water or excessive water shall be remained on the substrate that to be applied with GS 201.
Mixing GS 201 is supplied in 2 components, to generate a consistent slurry, pour the liquid component into a pail following by adding in the powder component gradually to the liquid. In the meantime, use a stirrer to stir the mixture until the mixture is free from lumps. Take note of the consistency of the slurry. The consistency of the slurry can be altered by reducing or adding in powder component. 47
Application Apply GS 201 with a stiff brush or spray onto the prepared surface with at least two coats. Interval of each coat should be 1-2 hours minimum. To avoid pin holes and ensure full coverage, apply each brush coat at different direction. For large space, spray is recommended by using a worm-gear type of spray equipment. For best result, apply GS 201 under shaded shelter to prevent rapid drying of the coating.
Curing The freshly applied GS 201 shall be protected from direct rain, dirt, oil, grease or other loose particle for at least 12 hours. It is foot trafficable after 24 hours and resistant to light mechanical stress after 3 days. Permanent water pressure resistance shall be achieved after a full hardening of 14 days.
Cleaning Clean tools and equipment immediately with clean water before the water proofer sets. Hardened material can only be removed mechanically. ii) Vandex BB 75 Vandex BB 75 is a cementitious, ready-mixed surface water proofer. Owing to its composition of cement, quartz with graded grain-size distribution and selected additives, VANDEX BB 75 is waterproof. It can be employed against active and passive water pressures. The initial and final bonding capability of VANDEX BB 75 is excellent, making it suitable to be applied to horizontal as well as vertical surfaces. It is durable, resistant to frost and heat after setting, but all the same permeable to vapour. VANDEX BB 75 is tested for use in contact with drinking water.
Mixing: Mix 25 kg of VANDEX with 4.5–6 litres of tap water in a clean container for at least 3 minutes to a lump-free, homogeneous consistency. Use a mechanical mixer.
Application: VANDEX BB 75 is applied with brush, trowel or suitable spray equipment. A maximum of 2 mm (approx. 4 kg/m²) can be applied in one working cycle. In most cases the application of more than one coat is recommended; please refer to relevant specification. It is recommended to apply the next coat whilst the previous coat is still damp on the surface. The previous coat must not be damaged during application of the following coat. The waiting time before applying the following coat depends on local climatic conditions such as humidity, temperature, etc. The previous coat is textured by suitable means whilst still plastic to form a key. To maintain workability of the material do not add water, simply re-stir the mixture.
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Fig 8.4 Vandex BB 75
iii) POLYDEK Polydek is a high performance, liquid-applied waterproofing membrane. It is consisting of a very elastic polymer with the inherent flexibility allows the membrane to accommodate movements in the substrate. Polydek is specially formulated to seal, decorate and simultaneously waterproof exterior surfaces in a two coats application. It may be applied by brush, roller or airless spray. Polydek is supplied in 20 litre pails.
Key Features •
•
Ease of application - Easily applied by brush, roller or airless spray. Surfaces can be damp or moist when applying Polydek. Solvent free - Polydek poses no problems to workers during application in enc losed areas because Polydek does not emit solvent fumes.
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•
• •
•
• •
•
Ease of maintenance - When maintenance is required after 5-10 years, the membrane surface can simply be cleaned and re-coated with a refresher or second top coat. Hairline cracks - Polydek bridges and seals non-moving hairline cracks. Vapor permeable - Coatings of Polydek allow two-way vapour transmission to release moisture and reduce efflorescence due to rising damp. Weather Resistant - Polydek has good weather ability and excellent resistance to ultraviolet degradation. Trafficability - Polydek can withstand regular foot traffic. Advantages over Sheet Membrane Systems - Polydek can be brush-applied to angle fillet and skirtings as well as to contours and irregularly angled surfaces. This circumvents the problem of measuring and cutting the sheet membrane to be torched onto the said areas. Polydek does not require honeycombs or hairline cracks in the concrete to be hacked, patched or grouted; unlike when using a sheet membrane system. Advantages over Solvent-Based Systems - Problems of bubb ling or pinholes are greatly reduced when using the water-based Polydek system because the moisture present in the membrane allows bubbles to escape.
Fig 8.5 POLYDEK
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Application: • • • • • • • • • • •
Concrete slab roof Roof terraces Asbestos roofs Asbestos roofs Planter boxes Bathrooms Laundries Gutters Drains Brickwork Fiber cement board
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8.2 CASE STUDY II 8.2.1 When strength of column doesn’t meat given requirements Additional strength is provided as follows: Scrub the entire column surface. Apply putty chemicals Apply EPOXY resin on the surface Stick fiber sheets to column with the help of epoxy applied. • • • •
8.2.2 Rectification of Concrete From the moment it is first cast, concrete is under attack from environmental factors - carbonation of concrete, ingress, chlorides, building movement, cracking and damage to concrete surfaces through abrasion. These factors reduce the concrete's natural ability to protect steel reinforcing, resulting in corrosion of the reinforcing. As steel corrodes it expands, causing the surrounding concrete to spall and fall off, endangering both property and passersby. This degeneration is known as "Concrete Cancer".
Fig 8.6 Improper compacting necessitating Rectification work. 52
Repair of concrete spalling (cancer) requires specialized techniques, skills and materials. In some States a contractor's license for concrete repairs is required. It is critical to identify the cause of the corrosion before the correct repair procedure can be established. Simply patching damaged areas can result in the corrosion being transferred to the adjacent area, which subsequently spalls. Rectification is done by using epoxy material. Epoxy resin is applied on Steel exposed area and filled with Rendroc RG. Grouting is then done with the help of grouting pipes.
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