Effect of cross-sectional rigidity on intermediate diaphragm spacing of steel-box girder bridges

Abstract

To control the distortion of box girder bridges and minimize the distortional stresses due to the torsional behavior when eccentric live loads are applied, it is necessary to install intermediate diaphragms in the box sections in the design of box girder bridges. This study estimated the distortional bi-moments and stresses of single-span rectangular steel box girder bridges by conducting a three-dimensional finite element analysis (FEA) considering various cross-sectional rigidities of the box girder sections. Based on the FEA, improved design equations for determining the distortional stresses and the appropriate intermediate diaphragm spacing were established considering various design parameters, such as cross-sectional rigidity, live load combination, normal stress ratios, and magnitude of the torsional moment. Finally, design recommendations were presented for the intermediate diaphragm spacing based on various design parameters.