Bridges - Intro
-
Upload
syed-ahmed-kabeer -
Category
Documents
-
view
215 -
download
0
Transcript of Bridges - Intro
-
8/22/2019 Bridges - Intro
1/22
Bridge Engineering
K I SYED AHMED KABEERSE732/12J21
-
8/22/2019 Bridges - Intro
2/22
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
-
8/22/2019 Bridges - Intro
3/22
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
-
8/22/2019 Bridges - Intro
4/22
* 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
-
8/22/2019 Bridges - Intro
5/22
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
-
8/22/2019 Bridges - Intro
6/22
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
-
8/22/2019 Bridges - Intro
7/22
Beam Bridge
Basic Beam Bridge
Actual Beam Bridge
http://www.pbs.org/wgbh/nova/bridge/meetbeam.html -
8/22/2019 Bridges - Intro
8/22
Arch Bridges
Keystone the wedge-shaped stone of an arch
that locks its partstogether
Abutments thestructures that support
the ends of the bridge
-
8/22/2019 Bridges - Intro
9/22
Arch Bridges
Works by
Compression
-
8/22/2019 Bridges - Intro
10/22
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
-
8/22/2019 Bridges - Intro
11/22
Types of Bridges
Arch Bridge
-
8/22/2019 Bridges - Intro
12/22
Similar to Cable-Stayed
Different construction method
Suspension Bridges
-
8/22/2019 Bridges - Intro
13/22
Works by Tension and Compression
Suspension Bridges
-
8/22/2019 Bridges - Intro
14/22
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
-
8/22/2019 Bridges - Intro
15/22
Types of Bridges
Suspension Bridge
Actual Suspension Bridge
Golden Gate Bridge, San Francisco, CA
-
8/22/2019 Bridges - Intro
16/22
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
-
8/22/2019 Bridges - Intro
17/22
Works by Tension AND Compression
Cable-Stayed Bridges
-
8/22/2019 Bridges - Intro
18/22
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
-
8/22/2019 Bridges - Intro
19/22
Types of Bridges
Cable-stayed Bridge
Actual Cable-stayed Bridge
Clark Bridge, Alton, IL
-
8/22/2019 Bridges - Intro
20/22
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.
-
8/22/2019 Bridges - Intro
21/22
George P. Coleman Bridge A Swing Beam Bridge
-
8/22/2019 Bridges - Intro
22/22
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