Exact distortional behavior and practical distortional analysis of multicell box girders using an expanded method

This paper presents an expanded method for exact distortional behavior of multicell box girders subjected to an eccentric loading. This method decomposes the eccentric loading into flexural, torsional and distortional forces by using the force equilibrium. From the force decomposition, the complex behavior of the multicell box girders can be decomposed and in turn the distortional behavior can be considered independently. Based on the method, a thin-walled box beam finite element, which can be applied to practical distortional analysis of straight multicell box girder bridges, is also developed in this study. The present box beam element possesses nine degrees of freedom per node to consider each separate behavior of multicell box girders. The validation of the present box beam element is demonstrated through a series of comparative studies using a conventional shell element and a box beam element proposed by other researchers. From the independent consideration of exact distortional behavior, the present box beam element unlike shell element will be useful for practicing engineers to easily determine distortional bimoments and stresses of multicell box girders.