Analysis of Curved Girder Bridges

Geometric, aesthetic, and economic considerations have led to the increased use of horizontally curved girders for highway bridges and interchange facilities which involve curved alignment. Despite the slightly higher fabrication costs associated with curving the girders, the net costs for such bridges, in certain cases, are lower than those for curved bridges with straight beams placed along the chords of the curved roadway. This overall economy is a result of the elimination of many substructure units (piers) and simplified form work necessary for the roadway slab. Since curved girders may be classified as linear elastic structures, all the various methods of linear structural analysis may be applied to the design of curved bridges. Although considerable analytical work has been done in this area, no attempt has been made to correlate the various methods of analysis or evaluate the degree of approximation inherent in several of the design procedures. The purpose of this paper is twofold. First, the fundamental differences between the behavior of individual straight girders and curved girders loaded normal to the plane of curvature will be established. Second, numerical results obtained from an approximate method of analysis widely used in the design of curved bridges3 will be compared with a rigorous analysis of curved grid systems.