Introduction of Bridge Engineering, components part of the bridge structure, classification of bridges

1. UNIT-III
Bridge Engineering
PROF .POOJA LONARE,ASST.PROFESSOR AT DEPARTMENT OF CIVIL ENGINEERING,GHRU
G H RAISONI UNIVERSITY | SAIKHEDA

2. Definition of bridge
Bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the
purpose of providing passage over the obstacle without closing the gap below.
IMPORTANCE OF BRIDGES
 Connects Difficult Terrains
 Easy Trade and Transportation of Goods
 Reduces Travelling Time
 Military use
 Political and Economic importance Less Emission due to displacement

3. COMPONENTS OF A BRIDGE
Abutment – Endpoints of the bridge. They are reinforced so that they can endure intense lateral pressures.
Pile (also known as beam, footing, and pier) – Reinforced concrete post that is driven into the ground to serve
as the leg or support for the bridge. The distance between piles is calculated so that is can support the rest of
the structure that will be laid on top of them.
Cap – Cap sits on top of the pile beam, providing additional support and dispersing the load to the piles below.
The combination of Pile and Cap elements is called Bent.
Girder or Span – One of the main components of the bridge that connects all the Piles beams.
Deck beam – Simple continuous decks are made from metal or reinforced concrete.
Barriers – Sides of the bridge decks usually have additional barrier components such as railings, handrails and ground
fixtures.

5. Site selection for bridge and investigation

6. Classification of bridges
Classification of Bridges (According to form (or) type of superstructures)
1.Slab bridge
2.Beam bridge
3.Truss bridge
4.Arch bridge
5.Cable stayed (or )suspended bridge
Classification of bridges (According to material of construction of superstructure)
1.Timber bridge
2.Concrete bridge
3.Stone bridge
4.R.C.C bridge
5.Steel bridge
6.P.C.C bridge
7.Composite bridge

7. LOADING ON BRIDGES
1. Dead Load
2. Live Load
3. Pressure
4. Centrifugal force
5. Earth Pressure
6. Seismic load
7. Water pressure
8. Wind load
9. Thermal forces

8. Classification of the various types of
bridges

9. 1. Beam bridges, also known as stringer bridges, are the simplest structural forms for bridge spans
supported by an abutment or pier at each end. No moments are transferred throughout the support,
hence their structural type is known as simply supported.
2.A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of
connected elements usually forming triangular units. The connected elements (typically straight) may be
stressed from tension, compression, or sometimes both in response to dynamic loads. The basic types
of truss bridges shown in this article have simple designs which could be easily analyzed by 19th and early
20th-century engineers. A truss bridge is economical to construct because it uses materials efficiently.
3.A cantilever bridge is a bridge built using cantilevers, structures that project horizontally into space, supported on
only one end. For small footbridges, the cantilevers may be simple beams; however, large cantilever bridges
designed to handle road or rail traffic use trusses built from structural steel, or box girders built from prestressed
concrete. The steel truss cantilever bridge was a major engineering breakthrough when first put into practice, as it
can span distances of over 1,500 feet (460 m).

10. 4.An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by
transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments
at either side. A viaduct (a long bridge) may be made from a series of arches, although other more economical
structures are typically used today.
5.Tied arch bridges have an arch-shaped superstructure, but differ from conventional arch bridges. Instead of
transferring the weight of the bridge and traffic loads into thrust forces into the abutments, the ends of the arches are
restrained by tension in the bottom chord of the structure. They are also called bowstring arches.
6.Suspension bridges are suspended from cables. The earliest suspension bridges were made of ropes or vines covered
with pieces of bamboo. In modern bridges, the cables hang from towers that are attached to caissons or cofferdams. The
caissons or cofferdams are implanted deep into the bed of the lake, river or sea.
7.A cable-stayed bridge has one or more towers (or pylons), from which cables support the bridge deck. A distinctive
feature are the cables or stays, which run directly from the tower to the deck, normally forming a fan-like pattern or a
series of parallel lines. This is in contrast to the modern suspension bridge, where the cables supporting the deck are
suspended vertically from the main cable, anchored at both ends of the bridge and running between the towers. The
cable-stayed bridge is optimal for spans longer than cantilever bridges and shorter than suspension bridges. This is the
range within which cantilever bridges would rapidly grow heavier, and suspension bridge cabling would be more costly.

11. Permanent and Temporary Bridges
Temporary Bridge
During construction of dams or bridges or during floods, temporary bridges are constructed at low
cost for temporary usage. These bridges are maintained at low cost. After construction of original
structure temporary bridges are dismantled. Generally timber is used to construct temporary
bridges.

12. Maintenance process of Bridge
1. The bearings of girders should be coated with oil from time to time.
2. The floor system of approaches and bridges should be properly
maintained.
3. The entire drainage system should be inspected for its proper
functioning.
4. The movement of foundations, if any, should be carefully inspected
and all attempts should be made to stop such further movement.
5. Determining location and types of reinforcing steel in concrete
Ensuring quality control on new concrete installations

13. Types of foundation in case of bridge
structure.
•Shallow foundation. Individual footing or isolated footing. Combined footing. Strip foundation.
Raft or mat foundation.
•Deep Foundation. Pile foundation. Drilled Shafts or caissons.

19. WELL FOUNDATION

20. Signaling
Railways are provided with signalling primarily to ensure that
there is always enough space between trains to allow a
following train to stop before it hits the one in front.
This is achieved by dividing each track into sections or
"blocks". Each block is protected by a signal placed at its
entrance.
signalling is one of the most important components of the
many which make up a railway system. Train movement safety
depends on it and the control and management of trains depends on
them.

21. Objects of signalling
The objectives of signalling are as follows.
(a) To regulate the movement of trains so that they run safely at maximum permissible speeds.
(b) To maintain a safe distance between trains that are running on the same line in the same direction.
(c) To ensure the safety of two or more trains that have to cross or approach each other.
(d) To provide facilities for safe and efficient shunting.
(e) To regulate the arrival and departure of trains from the station yard.
(f) To guide the trains to run at restricted speeds during the maintenance and repair of tracks.
(g) To ensure the safety of the train when it comes in contact with road traffic at level crossings.

22. Thanks & Wish you the luck
7/31/2020 22