Modeling maximum live load effects on highway bridges

The HL-93 live load model of the AASHTO LRFD was developed using a 1975 truck data set collected at a single site in Ontario Canada (Nowak; 1999). Because truck traffic volume and weights have increased and truck configurations have become more complex and because of site-to-site variations, the Ontario data may no longer be representative of current U.S. vehicular bridge loads. Therefore, U.S. Federal and State highway authorities are reviewing methods for updating the HL-93 load model and live load factors so that the design of new bridges and the safety assessment of existing bridges would be more consistent with current loading conditions.