Beam Bridges
- A beam bridge is the simplest kind of bridge
- The farther apart its supports, the weaker a beam bridge becomes
+ Cheap and cheerful
+ Easy to manufacture
- Not very beautiful
- Beam needs careful design
+ Easy to manufacture
- Not very beautiful
- Beam needs careful design
Box Girder Bridges
- Similar to beam bridges
- With well designed girders will be stronger than a simple beam bridge
+ Cheap and cheerful
+ Easy to manufacture
- Not very beautiful
- Girder needs careful design
+ Easy to manufacture
- Not very beautiful
- Girder needs careful design
Supporting Beams
- To improve the performance of a simple beam bridge the beam has to be supported
- There are three basic ways to do this:
- Arches
- Trusses
- Cables
Arch Bridges
- Arch bridges are one of the oldest types of bridge and have great natural strength
- Instead of pushing straight down, the weight of an arch bridge is carried outward along the curve of the arch to the supports at each end
- These supports (called abutments) carry the load and keep the ends of the bridge from spreading out
+ Very strong if well designed
+ Can be very beautiful
- Tend to be very heavy
- Need very strong abutments
+ Can be very beautiful
- Tend to be very heavy
- Need very strong abutments
Truss Bridges
- Are mostly empty space, but very effective
- Solid components (beams, arches etc.) are replaced by triangulated assemblies of thin (usually metal) members
+ Very good strength to weight performance
+ Possibility of lots of repeated parts reduces manufacturing costs
+ Can be incorporated into almost any design
+ Can be very beautiful
- Lots of parts to be manufactured
+ Possibility of lots of repeated parts reduces manufacturing costs
+ Can be incorporated into almost any design
+ Can be very beautiful
- Lots of parts to be manufactured
Suspension Bridges
- Apart from the towers, all the highly stressed parts of a suspension bridge are in tension
- A suspension bridge suspends the roadway from huge main cables, which extend from one end of the bridge to the other
- These cables rest on top of towers and are secured at each end by anchorages
+ Aesthetic, light and strong
+ Can span distances far longer than any other kind of bridge
- The most expensive bridges to build
- Susceptible to “wobble” if badly designed
+ Can span distances far longer than any other kind of bridge
- The most expensive bridges to build
- Susceptible to “wobble” if badly designed
Suspension Bridge Wobble
Cable Stayed Bridges
- In suspension bridges, the cables ride freely across the towers, transmitting the load to the anchorages at either end
- In cable-stayed bridges, the cables are attached to the towers, which alone bear the load
+ Undeniably beautiful
+ Compared to suspension bridges…
+ Require less cable
+ Are easier and faster to build
- Need stronger towers
+ Compared to suspension bridges…
+ Require less cable
+ Are easier and faster to build
- Need stronger towers
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