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Simple Beam BridgeA simple Beam design with a single span of approximately 6 metres.A beam or "girder" bridge is the simplest and most inexpensive kind of bridge. In its most basic form, a beam bridge consists of a horizontal beam that is supported at each end by piers. The weight of the beam pushes straight down on the piers. The beam itself must be strong so that it doesn't bend under its own weight and the added weight of crossing traffic. When a load pushes down on the beam, the beam's top edge is pushed together (compression) while the bottom edge is stretched (tension). Pre-stressed concrete is an ideal material for beam bridge construction; the concrete withstands the forces of compression well and the steel rods embedded within resist the forces of tension. Pre-stressed concrete also tends to be one of the least expensive materials in construction. But even the best materials can't compensate for the beam bridge's biggest limitation: its length. The further apart its supports, the weaker a beam bridge gets. As a result, beam bridges rarely span more than 80 metres. This doesn't mean beam bridges aren't used to cross great distances -- it only means that they must be daisy-chained together, creating what's known in the bridge world as a "continuous span." |
Structure information
Submitted by
Mike Hume
Location
Foss Basin, York
Date photo taken
April 2003
Materials used
reinforced concrete
Categories
Bridge
