Importance

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Abstract

The roll beam girder system for bridges has beams constructed from two end sections and a keystone center section. The two end sections have a top rolled steel beam welded to a bottom rolled steel beam, the top beam comprising about two-thirds of the total height of the section, the top beam being shorter than the bottom beam at the end joining the keystone section, the projecting end of the bottom beam having a slight camber. The keystone section has a top girder and triangular bottom key sections. The end sections and the keystone section have mating 45.degree. ends, with the ends of the top beam of the keystone section resting on the top of the projecting end of the bottom beam of the end section, a compression splice being formed by a row of nine bolts through the flanges on either side of the web of the mating end section and keystone section beams. Because of the slight camber of the projecting end of the end section and the nature of the compression splice, the bending moments are fixed, there is a slight curvature at the keystone section, and the load is borne by the end supports. Precast reinforced concrete planks may be welded transversely between the beams to form the floor of the bridge, which may optionally be smoothed with a two inch layer of concrete to form the roadway. The beams are supported by end supports. In this manner a roll beam bridge having a single span from 60 feet to 150 feet may be constructed.

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First Claim