Analysis of Suspended Curved Girder

A method of analysis is presented for curved girders on flexible supports for an interchange structure where geometrics, underclearance, and aesthetics dictated a suspended system. The structure, Ramp G, is suspended from an upper level steel girder that carries the Southwest Freeway over South Capitol Street in Washington, D.C. The procedures established for design reduced the indeterminate system essentially into two problems: (1) Analysis of a straight continuous girder on flexible supports; and (2) resolution of torsional forces caused by curvature. To check the assumptions and design procedures, the structure was field tested. Dead load measured reaction results compared well with computed dead load reactions. A 35-ton truck was used to perform live load tests. Of particular interest was a test run of the truck at 40 mph and a sudden application of the brakes to test for side sway and vibration. No appreciable sway or deflections were observed.