Truss Bridge

by ce on December 29, 2014

A truss bridge is a bridge composed of connected elements (typically straight) which may be stressed from tension, compression, or sometimes both in response to dynamic loads. Truss bridges are one of the oldesd types of modern bridges. This type of bridge structure has a fairly simple design and is particularly cheap to construct owing to its efficient use of materials. For purposes of analysis most truss bridges may be considered to be pin jointed where the straight components meet. A more complex analysis may be required where rigid joints impose significant bending loads upon the elements.

The advantages of truss bridges is that it is economical, light, strong and uses short members. Truss bridges are strong, since they are made of triangles, which are ridged. Another advantage about truss bridges is that they can be built in a convenient area, then place over where it has to bridge, although this is not always possible. That makes the truss bridge is that itakes up more space and can sometimes become a distraction to drivers.

Different member configurations of truss bridges are commonly employed to suit construction materials, spans, construction procedures, intended purposes etc. The best known truss bridges are the Warren truss, the Pratt truss, and the Howe truss. The Warren truss is the most common as well as the simplest, being pretty much one triangle beside the other. The Warren truss without vertical supports is used to bridge smaller spans while the Warren truss with vertical supports is used to bridge larger spans. The Warren truss is usually used to span 50-100 m gaps. Pratt truss bridges are made with diagonal supports that slant downward and toward the middle, except for the very end supports. The Howe truss is the opposite of the Pratt truss, because instead of slanting downward to the middle, the supports slant upward to the middle. Because the supports slant in the opposite direction, they handle compression forces, making it expensive when made in steel and also rarely seen.

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