EM-115 | Simple Suspension Bridge

Suspension bridges are among the oldest of all bridge designs. Their main supporting element is a flexible cable. Since cables are able to absorb high tensile forces while themselves having little dead-weight, they enable wide-span suspension bridges to be constructed. This makes it possible to bridge longer distances with no supporting pillars, such as over wide gorges. The sag of suspension bridge supporting cables is parabolic in shape, as the weights are attached at relatively short, constant intervals by way of vertical cables to the main supporting cables. The experimental setup represents a suspension bridge. The bridge consists of two parallel supporting cables with a roadway suspended between them. U-shaped hangers serve as vertical cables. They are attached to the main supporting cables at regular intervals, and hold the roadway. Deflection rollers act as pylons. The roadway acts upon the supporting cables as a distributed load, and can be loaded by additional weights. Two roadways with different stiffness are available: one rigid and one elastic roadway. The rigid roadway has a hinge in the middle. The hinge permits internal moments in the roadway occurring in response to uneven loading to be visualized – the roadway buckles. The experimental setup without roadway deals with free-hanging cables. Cables with different dead-weights are studied by attaching additional point loads directly to the supporting cables. The tensile forces in the supporting cables are determined with the aid of weights. The maximum sag is measured using a scaled rule. The scaled rule is fixed to a cross-arm.