BridgesBridges

Mr. O’RourkeMr. O’Rourke

TechnologyTechnology

What is a Bridge?What is a Bridge?

A structure built to span a valley, road, body of A structure built to span a valley, road, body of water or other physical obstacle for the purpose water or other physical obstacle for the purpose of passing over the obstacle.of passing over the obstacle.

HistoryHistory

The first bridges were made by nature itself. ex- The first bridges were made by nature itself. ex- a fallen tree over a stream.a fallen tree over a stream.Humans then began placing logs or planks Humans then began placing logs or planks across gaps they wanted to cross across gaps they wanted to cross

History History (cont’d)(cont’d)

The first complex bridges built were done by the The first complex bridges built were done by the ancient Greeks and Romans in the 13ancient Greeks and Romans in the 13 thth century. century. Some of these are still standing!Some of these are still standing!

Beam Bridge:Beam Bridge:

Horizontal beams supported at each end Horizontal beams supported at each end by piers. The weight at the top of the by piers. The weight at the top of the beam pushes straight down onto the piers.beam pushes straight down onto the piers.

Arch Bridge:Arch Bridge:

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

Truss Bridge:Truss Bridge:

Trusses are used to stiffen and support a Trusses are used to stiffen and support a bridge by distributing the loads and forces bridge by distributing the loads and forces acting upon the bridge based on the acting upon the bridge based on the positions of the vertical, horizontal and positions of the vertical, horizontal and diagonal chords. diagonal chords. 

Suspension Bridge:Suspension Bridge:

Has cables suspended between towers, plus Has cables suspended between towers, plus vertical suspenders which carry the weight of the vertical suspenders which carry the weight of the deck (load bearing portion).deck (load bearing portion).

Cable-Stayed Bridge:Cable-Stayed Bridge:

Like suspension bridges, cable-stayed bridges are held Like suspension bridges, cable-stayed bridges are held up by cables. However, in a cable-stayed bridge, less up by cables. However, in a cable-stayed bridge, less cable is required and the towers holding the cables are cable is required and the towers holding the cables are proportionately shorter. proportionately shorter.

Forces Acting On A Bridge:Forces Acting On A Bridge:

Compression Tension Bending Torsion Shearing

Big Sur Bridge, CaliforniaBig Sur Bridge, California

Millau Bridge, FranceMillau Bridge, France

Donghai Bridge, ChinaDonghai Bridge, China

Tappan Zee Bridge, NYTappan Zee Bridge, NY

Battle Ground Bridge, WashingtonBattle Ground Bridge, Washington

Brooklyn and Manhattan Bridge, Brooklyn and Manhattan Bridge, NYC.NYC.

Pont De Quebec Bridge, CanadaPont De Quebec Bridge, Canada

Grant Memorial Bridge, OhioGrant Memorial Bridge, Ohio