Bridges

Important Words• Span: the distance between two bridge supports

(column, tower, canyon walls…)• Abutment:

a. The part of a structure that bears the weight or pressure of an arch. b. A structure that supports the end of a bridge. c. A structure that anchors the cables of a suspension bridge.

• Girder: a beam, made of steel, wood, or reinforced concrete, used as a main horizontal support in a building or bridge – can be a box girder or truss girder

More Important Words

• Compression: a force that acts to compress or shorten the thing it is acting on.

• Tension: a force that acts to expand or lengthen the thing it is acting on.

http://www.howstuffworks.com/bridge.htm

Beam Bridge• A rigid horizontal structure that is resting on two

piers, one on each side.Load

Compression

Tension

Reaction Force Reaction Force

http://www.brantacan.co.uk/starterpages.htm

Beam Bridge• Typical Span

Lengths: 10m - 200m• World's Longest:

Ponte Costa e Silva, Brazil

• Total Length: 700m• Center Span: 300m

Truss Bridge• Supporting lattice

work added to many types of bridges. Trusses are skeletal structures made up of many small beams (normally in the shape of triangles). As the size of a beam bridge increases, so must the size of the truss

Cantilever Bridge• Cantilever bridges

are a modified form of beam bridge, with the support being placed not at the end, but somewhere in the middle of the span. A cantilever is a structure or beam that is unsupported at one end but supported at the other, like diving boards. 

http://www.richmangalleries.com/cantilever_bridges.htm

Forces in a Truss Bridge

Truss Bridge• Typical Span

Lengths: 40m - 500m

• World's Longest: Pont de Quebec

• Total Length: 863m

• Center Span: 549m

www.sepaq.com/Photos/J380/batPontQuebecC.jpg

Arch Bridge• An arch bridge is a

semicircular structure with abutments on each end. The arch naturally brings the weight (a force) of the load from the roadway to the abutments. Used by the ancient Romans. Can be made out of brick or stone.

Load

Compression

Reaction Force

http://www.matsuo-bridge.co.jp/english/bridges/index.shtm

Arch Bridge

• Typical Span Lengths: 40m - 150m

• World's Longest: New River Gorge Bridge, U.S.A.

• Total Length: 924m

• Center Span: 518m

Suspension Bridge• The deck of the bridge is held up by cables that are

strung across the water or canyon. In modern suspension bridges, there are two towers over which the main cables are strung. Numerous vertical or hanging cables (rods) support the road and are attached to the main cables. Thus, the towers are supporting the majority of the road deck’s weight. The main cables must be anchored on either end of the bridge.

Load

Compression

Reaction Force

Tension

http://www.brantacan.co.uk/starterpages.htm

Suspension• Typical Span

Lengths: 70m - 1,000m+

• World's Longest: Akashi Kaikyo Bridge, Japan

• Total Length: 3,911m

• Center Span: 1,991m

www.bergen.org/.../2002/wp_bridge/akashi.jpg

Cable Stayed Bridge• A continuous beam with one or more towers built

above piers. From these towers, cables stretch down diagonally (usually to both sides) and attach to the girder to support the bridge deck. The cables can all attach at the top of the tower (fan) or at various points along the tower (harp).

LoadTension

Compression

Reaction Force

http://www.brantacan.co.uk/starterpages.htm

Cable Stayed

• Typical Span Lengths: 110m - 480m

• World's Longest: Tatara Bridge, Japan

• Total Length: 1,480m

• Center Span: 890m www.kawadaken.co.jp/jigyo/image/04_tatara.jpg