Abstract

Current American Association of State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO-LRFD) provided several equations for distribution factor of moment and shear of multi-cell box-girder bridges. However, the equations involved a large number of parameters, but the preliminary study shows that it is not compatible with finite element results. In many cases, the change in straining actions due to skew angle, continuity and effect of diaphragms result in tremendous errors in the results. So, this study aims at evaluating the accuracy of these equations by doing a parametric study to determine the effectiveness of various parameters on lateral distribution of live loads. To this end, three samples of numerical model bridges were considered and analyzed by means of finite element method. The results indicate that the span length, number of box, number of lanes and web spacing significantly had an effect on the exterior and interior moment distribution factor of bridges. Proposed improved equations were deduced accordingly for AASHTO-LRFD, (2007) moment loads. Results from the proposed equations are consistent with numerically derived results from grillage and finite element method.

Key words: Multi-cell, box-girder, distribution factor, skews bridges, grillage method, truck load.