Bridges - Intro

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Bridge Engineering

K I SYED AHMED KABEERSE732/12J21


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700 A.D. Asia

100 B.C. Romans

Natural Bridges

Clapper Bridge

* Tree trunk* Stone

* The Arch* Natural Cement

Roman Arch Bridge

History of Bridge Development

Great Stone Bridge in China

* Low Bridge* Shallow Arch

1300 A.D. Renaissance

* Strength ofMaterials

* MathematicalTheories

* Development ofMetal


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First Cast-Iron Bridge

Coal brookdale, England

1800 A.D.

Britannia Tubular Bridge

1850 A.D.

Wrought Iron

Truss Bridges

Mechanics of

Design

Suspension Bridges

Use of Steel for thesuspending cables

1900 A.D.

1920 A.D.

* PrestressedConcrete

* Steel

2000 A.D.

History of Bridge Development


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* A bridge is a structure that permits you to cross over anobstacle.

* Suppose you lay a plank across a brook. You have a bridge. Ifthe plank is thin in relation to its length, it will sag. In fact, ifit is too long, it will collapse. This shows that you mustconsider the weight of a bridge itself---the dead load.

* If you stand at the middle of the plank, it sags even more.So, you must provide for the weight of whatever yourbridge is designed to carry---the live load.

* Also, when you walk across the plank, it bounces under you,illustrating the effect of a moving live load.

* Finally, there is a wind load. A strong wind pushes againstthe sides, lifts the deck, shakes the whole structure.Certainly the force of the wind is something to keep in mind.

Introduction


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Classification can be based on

Its function or purpose

The materials of construction Their nature of life

Their relative position of floor

Their type of superstructure

Their method providing clearance

Types of bridges


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A beam or "girder" bridge is the simplest and mostinexpensive kind of bridge.

In its most basic form, a beam bridge consists of ahorizontal beam that is supported at each end bypiers. The weight of the beam pushes straight downon the piers.

The beam itself must be strong so that it doesn't bendunder its own weight and the added weight ofcrossing traffic.

When a load pushes down on the beam, the beam'stop edge is pushed together (compression) while thebottom edge is stretched (tension).

Beam Bridge


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Beam Bridge

Basic Beam Bridge

Actual Beam Bridge
http://www.pbs.org/wgbh/nova/bridge/meetbeam.html


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Arch Bridges

Keystone the wedge-shaped stone of an arch

that locks its partstogether

Abutments thestructures that support

the ends of the bridge


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Arch Bridges

Works by

Compression


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Arch Bridge Arch bridges are one of the oldest types of bridges

and have great natural strength.

Instead of pushing straight down, the weight of anarch bridge is carried outward along the curve of thearch to the supports at each end.

These supports, called the abutments, carry the load

and keep the ends of the bridge from spreading out.

Types of Bridges


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Types of Bridges

Arch Bridge


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Similar to Cable-Stayed

Different construction method

Suspension Bridges


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Works by Tension and Compression

Suspension Bridges


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Aesthetic, light, and strong, suspension bridges canspan distances from 2,000 to 7,000 feet -- far longerthan any other kind of bridge.

They also tend to be the most expensive to build. True to its name, a suspension bridge suspends the

roadway from huge main cables, which extend fromone end of the bridge to the other.

These cables rest on top of high towers and aresecured at each end by anchorages.

Inside the anchorages, the cables are spread over alarge area to evenly distribute the load and to preventthe cables from breaking free.

Types of BridgesSuspension Bridge


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Types of Bridges

Suspension Bridge

Actual Suspension Bridge

Golden Gate Bridge, San Francisco, CA


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Cable-Stayed Bridges

Piers the vertical supporting structures Cables thick steel ropes from which the decking is

suspended

Decking the supported roadway on a bridge


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Works by Tension AND Compression

Cable-Stayed Bridges


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Cable-stayed Bridge Cable-stayed bridges may look similar to suspensions

bridges -- both have roadways that hang from cablesand both have towers.

Two bridges support the load of the roadway in verydifferent ways.

The difference lies in how the cables are connected tothe towers. In suspension bridges, the cables ride freely

across the towers, transmitting the load to theanchorages at either end. In cable-stayeded bridges, the cables are attached to

the towers, which alone bear the load.

Types of Bridges


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Types of Bridges

Cable-stayed Bridge

Actual Cable-stayed Bridge

Clark Bridge, Alton, IL


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Moveable Bridge

has a deck that moves.

A swing bridge has a deck that rotates around acenter point;

a drawbridge has a deck that can be raised andlowered;

a bascule bridge deck is raised withcounterweights like a drawbridge;

the deck of a lift bridge is raised vertically like amassive elevator.


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George P. Coleman Bridge A Swing Beam Bridge


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Importance

Bridge is the KEY ELEMENT in a TransportationSystem

It controls the capacity of the system

Highest cost per km

If a bridge fails the system fails

Documents

Bridges - Intro