Analysis of the distortion of cantilever box girder with inner flexible diaphragms using initial parameter method

In this paper, the distortion of cantilever box girders with inner flexible thin diaphragms is investigated under concentrated eccentric loads using initial parameter method (IPM), in which the in-plane shear strain of diaphragms is fully considered. A high-order statically indeterminate structure was established with redundant forces, where the interactions between the girder and diaphragms were indicated by a uniform distortional moment. Based on the compatibility condition between the girder and diaphragms, solutions for the distortional angle and the warping function were obtained by using IPM. The accuracy of IPM was verified by finite element analysis for the distortion of cantilever box girders with 2, 5 and 9 diaphragms under three diaphragm thicknesses, respectively. Taking a lifting mechanism as an example, parametric studies were then performed to examine the effects of the diaphragm number and thickness, the ratio of height to span of the girder, the hook's location and the wheels' positions on the distortion of cantilever box girders. Numerical results were summarized into a series of curves indicating the distribution of distortional warping stresses and displacements for various cross sections and loading cases.