Bridge Building History & Bridge Types
Jan 19, 2016
Bridge BuildingHistory & Bridge Types
History
Essential in the development and exploration of North America
Allowed pioneers & explorers to move goods and services from one area to another in shorter periods of time◦Without bridges they would have to wait for
flooded rivers to recede/dry up or go miles out of their way
◦Crossing river beds was often dangerous Wheels were skinny Sank into river beds losing lives and goods
History
Early bridges occurred naturally (were fallen logs, not good for movement of goods)
Earliest known man-made bridge was a primitive rope bridge◦Pre-cursor to suspension bridges
Bridge Types
Rope BridgesStone Arch BridgesSteel Arch BridgesSuspension BridgesTruss BridgesCantilever Bridges
Rope Bridges
Rope bridges (China) still used today◦Strengths (cheap, relatively easy to build, move
goods w/ pack animals)◦Weaknesses (susceptible to high winds, not big
enough to move vehicles)
Stone Arch Bridge
Stone arch bridges◦Strongest and most durable◦Stones are in compression◦Key Stone!
Expensive (stones and cost of labour)
Steel Arch Bridge
Steel arch bridges◦Capable of covering great spans◦Often combined with other bridge components
(trusses, cables, etc.)◦Arch in compression (cables in tension, trusses
in both)
Suspension Bridges
Suspension bridges◦Can span the longest◦Extremely efficient (material wise)◦Use cables under tension to support bridge
deck
George Washington Bridge
George Washington Bridge◦2 cables – 3 feet in diameter, 1 mile long◦Each cable has 26,000 strands; together is 107,000
miles (4x around the earth)◦Can support 80,000 tons
Truss Bridge
Truss bridge – distribute the load ◦Wood
Easy to build Capable of carrying heavy loads (rigid & strong)
◦Steel Not as good for long spans Can be quickly assembled or pre-fabricated Can support great loads Used typically for railway bridges
Cantilever Bridge
Cantilever bridge◦Type of truss bridge◦Built towards centre from each bank and joined
with a middle section◦Most challenging is setting centre section in
place