Bridges
What is a Bridge? A bridge is a structure built to span a physical distance without closing off the area underneath Used to transport people, cars, trains, and utilities across bodies of water, valleys, or roads.
Bridge Types Simple Beam Arch Truss Cantilever Cable Stayed Suspension
2Main Forces Tension – Pulling apart force that occurs on the bottom of a bridge when it dips Compression – Pushing together force that occurs on the top of a bridge when it dips
2 Main Forces When the tension force causes the bridge to break its called snapping. When the compression force causes the bridge to break its called buckling.
Beam Bridge Compression Tension The simplest type of bridge, these are just a horizontal structure with a support at each end. Beam bridges are limited with how far they can span between supports These bridges typically have a short span range, up to 200 feet
Arch Bridge Compression Tension Arch Bridges use one or more arches to distribute the compressional forces down through the vertical supports These bridges typically span 200-800 feet
Truss Bridge Compression Tension A truss bridge uses a lattice of triangular units to handle the compression tension forces These bridges typically have a short to medium span range, 100-400 feet
Cantilever Bridge Compression Tension Cantilever bridges use a horizontal beam supported at one end only They are often used in pairs These bridges typically have a medium span range, up to 1800 feet
Suspension Bridge Compression Tension Suspension bridges are held up by cables that extend from anchors at either end of the bridge. The cables pass over vertical supports (towers) in the middle and have more cables that extend down to the roadway These bridges typically span 2000-7000 feet
Cable Stayed Bridge Compression Tension Cable Stayed bridges have cables that extend from the towers directly down to the roadway These bridges typically have a medium to long span range
Other Forces Torsion forces are the twisting and rotating forces that are a particular concern for suspension bridges Shear forces are when two fastened structures are forced in opposite directions, ripping them apart Resonance is the vibration of a body at its natural frequency because of the action of a vibrating source at the same frequency
Tacoma Narrows Bridge Video
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