Construction Of A Viaduct/Bridge: An Overview

The following project focuses on the viaduct and its various parts, describing their individual characteristics as well as the methods being used for its construction.

1. CONSTRUCTION OF A VIADUCT/BRIDGE: AN OVERVIEW SUBMITTED BY :- PROJECT GUIDE :- SOURAV GOSWAMI Mr . S.C MITRA MVJ COLLEGE OF ENGINEERING, BANGALORE MANAGER –(PROJECT) ( 02.01.2016 to 09.01.2016) RVNL - KOLKATA

2. ACKNOWLEDGEMENT I would like to express my special thanks of gratitude to Mr. Amit Kumar Roy (CPM/LINE, RVNL Kolkata), Mr. Avijit Roy (GM/P, RVNL KOLKATA), Mr. S.C.Mitra (MANAGER, PROJECT, RVNL KOLKATA), Staffs and Supervisors of RVNL and GAMMON INDIA LIMITED who gave me the golden opportunity to do this wonderful project on the topic CONSTRUCTION OF METRO RAIL BRIDGE , which also helped me in doing a lot of Research and I came to know about so many new things. I am really thankful to them. Lastly, I would also like to thank my parents who helped me a lot in finalizing this project within the limited time frame. SOURAV GOSWAMI (PROJECT INTERN)

3. SUMMARY The following project focuses on the viaduct and its various parts, describing their individual characteristics as well as the methods being used for its construction. The project was done in a brief span of seven days. The topics discussed here were the subjects of my inspection. The Project was done as summer internship under Rail Vikas Nigam Limited ( RVNL ) , in association with Gammon India Limited. This internship has helped me gather practical knowledge of the onsite activities that takes place while constructing a viaduct/bridge. SOURAV GOSWAMI ( PROJECT INTERN )

4. CONTENT BRIDGE PILE PILING ACTIVITY PILE CAP PIER PIER CAP BEARING SEGMENT SEISMIC RESTRAINER CASH BARRIER

5. BRIDGE A   bridge is a structure built to span physical obstacles without closing the way underneath such as a body of water, valley, or road, for the purpose of providing passage over the obstacle. There are many different designs that all serve unique purposes and apply to different situations. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed and anchored, the material used to make it, and the funds available to build it .  During the design process, every bridge can be divided broadly into three parts: -Superstructure. -Substructure. -Foundation. MAJOR PARTS OF A BRIDGE The major parts of a bridge are as follows: - Pile. - Pile Cap. - Pier. - Pier Cap. - Bearing. - Segment. - Seismic Restrainer. - Crash Barrier.

6. PILE There are three types of pile foundations according to their construction methods: 1.Driven piles, 2.Cast-in-situ piles, and 3.Driven and cast-in-situ piles. Pile foundation selection depends on the soil data received from soil exploration bore holes at different depths. Selection of pile foundation types and length depends on following conditions: -Soil conditions -Loads from structures -Nature of loads -Number of piles to be used -Cost of construction There are three types of pile foundation based on load transfer mechanism: -End bearing piles -Friction bearing piles -Combination of end bearing and friction bearing piles. The purpose of pile foundations is: – To transmit the buildings loads to the foundations and the ground soil layers whether these loads vertical or inclined – To install loose cohesion less soil through displacement and vibration. – To control the settlements; which can be accompanied by surface foundations. – To increase the factor of safety for heavy loads buildings.

7. PILING ACTIVITY SITE CLEARING AND PLACING BARRICADING. SURVEYING WORK. CASING AND DRIVING. BORING. CHECKING FOR FOUNDING LEVEL. MAKING AND LOWERING OF REINFORCEMENT CAGE. LOWERING OF TREMMIE PIPE. FLUSHING. CONCRETING.

8. PILE CAP A  pile cap  is a thick concrete mat that rests on concrete or timber piles that have been driven into soft or unstable ground to provide a suitable stable foundation. It usually forms part of the  foundation of a building, typically a multi-story building, structure or support base for heavy equipment. The cast  concrete pile cap distributes the load of the building into the piles. A similar structure to a pile cap is a "raft", which is a concrete foundation floor resting directly onto soft soil which may be liable to  subsidence. The mat is made of concrete which is an aggregate of small rocks and cement. This mixture has to be supported by a framework to avoid sagging and fracture whilst setting. This process is known as shuttering and  reinforcing. The materials used are long twisted steel bars between the piles held in shape by thinner tie wires. Once this steel mat is laid, timber is attached around the perimeter to contain the wet concrete mixture. Once poured, (usually as a series of small loads), the concrete is stirred to remove any air pockets that might weaken the structure when set. The concrete undergoes a chemical change as it hardens and this produces a lot of heat. Sometimes, if the mass of concrete is very large, pipes carrying refrigerant coolant are used in the mass to assist the setting process to prevent the concrete from cracking.

9. PIER A  pier  is a raised structure typically supported by well-spaced piles or pillars. Bridges, buildings, and walkways may all be supported by piers. Their open structure allows tides and currents to flow relatively unhindered, whereas the more solid foundations of a quay or the closely spaced piles of a wharf can act as a breakwater, and are consequently more liable to silting. Piers can range in size and complexity from a simple lightweight wooden structure to major structures extended over 1600 meters.

10. PIER CAP The upper or bearing part of a bridge pier, usually made of concrete or hard stone. It is designed to distribute concentrated loads evenly over the area of the pier.

11. BEARING A  bridge bearing  is a component of a bridge which typically provides a resting surface between bridge piers and the bridge deck. The purpose of a bearing is to allow controlled movement and thereby reduce the stresses involved. Movement could be thermal expansion or contraction, or movement from other sources such as seismic activity. There are several different types of bridge bearings which are used depending on a number of different factors including the bridge span. The oldest form of bridge bearing is simply two plates resting on top of each other. A common form of modern bridge bearing is the elastomeric bridge bearing. Another type of bridge bearing is the mechanical bridge bearing. There are several types of mechanical bridge bearing, such as the pinned bearing, which in turn includes specific types such as the rocker bearing, and the roller bearing. Another type of mechanical bearing is the fixed bearing, which allows rotation, but not other forms of movement. The purpose of a bridge bearing is to support the superstructure at a constant elevation, to carry all forces from the superstructure into the substructure and to allow necessary superstructure motions to take place. Forces to be applied to bridge bearings can come from any of the loads associated with the bridges.

12. SEGMENT A  segment  is a bridge built in short sections (called segments), i.e., one piece at a time, as opposed to traditional methods that build a bridge in very large sections. The bridge is made of concrete that is either cast-in-place (constructed fully in its final location) or precast concrete (built at another location and then transported to their final location for placement in the full structure). These bridges are very economical for a span of 28m or so. For example, the span of 28m is divided into segments (FS1, FS2, FS3, FS4, FS5, RS1,RS2,RS3,RS4,RS5) where the first and last segments are of 2m and the rest are of 3m. In cast-in-place bridges, the falsework is connected to the previously installed concrete and allowed to cantilever freely. Next, the permanent reinforcing steel and supports are installed. Finally, the concrete is placed and cured, freeing the falsework to be moved. In pre-cast bridges, the concrete segment is constructed on the ground, and then transported and hoisted into place. As the new segment is suspended in place by the crane, workers install steel reinforcing that attaches the new segment to preceding segments. Each segment of the bridge designed to accept connections from both preceding and succeeding segments.

13. SEISMIC RESTRAINER Most bridges have movement joints to accommodate thermal expansion an contraction without inducing large forces in the bridge. During an earthquake, the joints pose a hazard. If the relative displacement of adjacent frames or girders exceeds the available seat width, the span will collapse. The seismic restrainer is provided at the bridge construction to prevent or minimize the relative displacement caused due to the seismic waves induced by earthquake or tsunami.

14. CRASH BARRIER A wall is cast around the pier around the road level, which is known as Crash Barrier. The gap of 25mm is maintained between pier and crash barrier. Crash Barriers are generally provided to protect the pier from damages by the road accidents caused by the vehicles when it gets crashed with the pier.

15. THANK YOU