Assessment of flexural lateral load distribution methodologies for stringer bridges

Methods for determining flexural lateral load distribution have received significant attention in recent years as a result of the transition from the traditional “ s -over” approach of the AASHTO Standard specification to the semi-empirical based approach of the AASHTO LRFD. This attention has included evaluation of in-service behavior, the development of simplified equations, and assessment of contributing parameters. It is evident that an understanding of load distribution behavior is critical for both design and load rating of stringer bridges because the magnitude of this load sharing determines the resistance that must be provided by the primary load carrying members. However, methods of determining lateral load distribution behavior have potential discrepancies that need to be addressed including relationships of member load effects, influence of secondary members, and impact of boundary conditions. This study investigates a number of methods used by researchers to determine load distribution factors for slab–girder bridges with the goal of determining the appropriate methods for analysis purposes. Results from the investigation, indicate that current methodologies yield similar trends, but potential errors may arise without proper consideration of boundary conditions and internal member load effects.