Some Design Problems of Large Box Girder Bridges

First, the procedures for analyzing asymmetrical transverse loads on box girders and the related problem of intermediate diaphragm trusses were analyzed. Three different methods were used to cross-check the results: one based on influence lines derived by the accurate elastic analysis of box girders and two approximate methods with simplified statistical model where box girder is transformed to an equivalent plate girder. Second, the stability problems of thin plates forming the box girder were investigated. Using buckling coefficients now available for different geometry and stress conditions of the panel under consideration, the spacing of longitudinal stiffeners was obtained graphically. Transverse stiffeners were designed in two different ways: (1) as verticals of a double Pratt truss; and (2) as intermediate stiffeners for two adjacent panels.