2Table of contents What is a bridge.? Different types of bridges. Descriptions.History Working.CulvertsType of culvertsDepictionReferences.
3BridgeBridge is a structure built to span a valley, road, river, body of water, or any other physical obstacle.Designs of bridges will vary depending on the function of the bridge and the nature of the area where the bridge is to be constructed.
4Great Stone Bridge in China History of Bridge Development100 B.C. Romans2,104 years ago700 A.D. Asia1,304 years agoClapper BridgeRoman Arch BridgeTree trunkStoneArch designevenly distributesstressesNatural concretemade from mudand strawGreat Stone Bridge in ChinaLow bridgeShallow archAllows boatsand water to passthrough
5History of Bridge Development 19001920Truss BridgesMechanics of DesignWood2000Suspension BridgesUse of steel in suspending cablesPrestressed ConcreteSteel
6Basic ConceptsSpan - the distance between two bridge supports, whether they are columns, towers or the wall of a canyon.Force -CompressionTensionCompression –Tension -Concrete has good compressive strength, but extremely weak tensile strength. What about steel cables?
7Basic Concepts Beam - a rigid, usually horizontal, structural element PierPier - a vertical supporting structure, such as a pillarCantilever - a projecting structure supported only at one end, like a shelf bracket or a diving boardLoad - weight on a structure
8Types of Bridges There are six main types of bridges: beam bridges cantilever bridgesarch bridgessuspension bridgescable-stayed bridges andtruss bridges
9Bridge Design Engineering Considerations Ground conditions Availability of materialsAesthetic properties
10Beam BridgesConsists of a horizontal beam supported at each end by piers. The weight of the beam pushes straight down on the piers.The farther apart its piers, the weaker the beam becomes.This is why beam bridges rarely span more than 75m.
11Box Girder Bridge Box shaped cross section Good in torsion More expensive to maintainCommonly precast
17Arch bridges The arch has great natural strength. Thousands of years ago, Romans built arches out of stone.Today, most arch bridges are made of steel or concrete, and they can span up to 800 feet.
18Arch BridgesForcesThe arch is squeezed together, and this squeezing force is carried outward along the curve to the supports at each end.The supports, called abutments, push back on the arch and prevent the ends of the arch from spreading apart.
20Suspension BridgesThis kind of bridges can span 800m to 2500m -- way farther than any other type of bridge!Most suspension bridges have a truss system beneath the roadway to resist bending and twisting.
21ForcesIn all suspension bridges, the roadway hangs from massive steel cables, which are draped over two towers and secured into solid concrete blocks, called anchorages, on both ends of the bridge.The cars push down on the roadway, but because the roadway is suspended, the cables transfer the load into compression in the two towers.The two towers support most of the bridge's weight.
27Truss Bridge Typical Span Lengths 40m - 500m World's Longest Pont de QuebecTotal Length863mCenter Span549mA Matsuo Example2nd Mameyaki BridgeAll beams in a truss bridge are straight. Trusses are comprised of many small beams that together can support a large amount of weight and span great distances
29Floating BridgePontoon bridges are supported by floating pontoons with sufficient buoyancy to support the bridge and dynamic loads.While pontoon bridges are usually temporary structures, some are used for long periods of time.Permanent floating bridges are useful for traversing features lacking strong bedrock for traditional piers.Such bridges can require a section that is elevated, or can be raised or removed, to allow ships to pass.