The Structure Behind Bridges

shawlaskewvilleUrban and Civil

Nov 29, 2013 (3 years and 6 months ago)

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The Structure Behind Bridges

General Description


A bridge is a structure built to cross a valley,
road, railroad track, river, body of water, or
any other physical obstacle, for the purpose of
providing passage over an obstacle.


The designs of bridges vary depending on the
function of the bridge and the nature of the
terrain where the bridge is being built.


History of Bridges


The Romans were the most superior bridge
builders of their time.


They built arch bridges and aqueducts

that
could stand in conditions that would damage
or destroy earlier designs, some of their
structures still stand today.


The
Alcántara

Bridge in Spain is an example.

Alcántara

Bridge


Types of Bridges


There are six main types of bridges:


B
eam bridges


C
antilever bridges


A
rch bridges


S
uspension bridges


C
able
-
stayed bridges


T
russ bridges

Types of Bridges


Beam bridges
contain horizontal beams that
support at each end by piers.


The weight on top of the beam pushes straight
down on the piers at either end of the bridge.


Cantilever bridges
are built using cantilevers.
They are horizontal beams that only supported
on one end.


The largest cantilever bridge is the Quebec Bridge in
Quebec, Canada.

Quebec Bridge


Types of Bridges


Arch bridges
are arch
-
shaped and have
abutments at each end. The weight of the bridge
is thrust into the abutments at either side.



This method was first introduced by the Greeks.


Suspension bridges

are suspended from cables.


In modern bridges, the cables hang from towers that
are attached to caissons or cofferdams.


The longest suspension bridge in the world is the
Akashi
Kaikyo

Bridge

(12,826

feet.)

Akashi
Kaikyo

Bridge


Types of Bridges


Cable
-
stayed bridges
are held up by cables.


However, in a cable
-
stayed bridge, less cable is
required and the towers holding the cables are
shorter.


Truss bridges
are composed of connected
elements. They have a solid deck and a lattice of
pin
-
jointed girders for the sides.


They are made of metals such as wrought iron and
steel or sometimes of reinforced concrete.

Truss Bridge


Similarities/Differences of a Bridge


Bridges may be classified by how the forces of
tension, compression, and bending are
distributed through their structure.


Most bridges will employ all of the principal
forces to some degree, but only a few will
dominate.


F
orces may be distributed among a large
number of members, as in a truss.

Work Cited Page


“Bridges”
http://en.wikipedia.org/wiki/Bridge


“All About Bridges”
http://www.pbs.org/wgbh/buildingbig/bridge


“How Bridges Work”
http://www.howstuffworks.com/bridge.htm