ARCH BRIDGES
-Arch bridges are one of the oldest types of bridges
-The arch is a shape of great natural strength
-The weight of the bridge is carried to the down and to the side by the arch
-All portions of the arch support the same weight
-Economically cheap
- Some arch bridges have a series of arches under the surface.
Arch Bridges vary in length because….
Length of span
Width of deck
Height above ground or water
Height of piers
Ratio of span to width of pier
Ratio of span to rise
Number of spans
Materials
Segmented or curved
Type of construction
Construction
Today, arch bridges are made of both steel and reinforced concrete. It is difficult to build arch bridges because the structure is unstable until the two spans are connected in the middle. A technique that is often used is called scaffolding, which involves supporting each span until they can be connected. Another technique that has been becoming more popular involves supporting the spans with cables that are attached to the ground on either side of the construction. This method allows construction to take place without any disruption of activities under the bridge, such as traffic.
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Sydney Harbour Bridge in Australia
-Longest single arch bridge in the world -Spans 550 meters of water -Held together by six million rivets -Chief Engineer was Doctor John Bradfield -Took nine years to build and opened in 1932 -39,000 tons of structural steel -Founded on sandstone rock excavated to 12m -Each half was built using cranes and attached in the middle -Connects Dawes Point and Milsons point |
Bixby Creek Bridge, California
-Made of reinforced concrete -110 meter main span -80 meters above water -Designed in 1931 by Buckland and Taylor -One of the largest single arch concrete bridges in the world
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