The live load distribution factor is a very important parameter in both the design of new bridges and the evaluation of in-service bridges. Studies have shown that there can be large discrepancy between the actual load distribution factors of field bridges and the load distribution factors predicted by bridge design codes. In addition, the load distribution factor is always treated as a constant in bridge assessment even though it is a random variable with certain statistical properties. In this study, the reliability indexes of 15 prestressed concrete girder bridges designed following the AASHTO LRFD code are calculated by considering the randomness of the load distribution factors induced by the random vehicle transverse position. It is found that there is a considerable increase in the calculated bridge reliability indexes, especially for short-span bridges, when the load distribution factor is modeled as a random variable with the statistical properties obtained from numerical simulations. This suggests that vehicle transverse position is one important factor that can be considered if a refined analysis is desirable when traditional evaluation methods predict unsatisfactory bridge assessment results. The findings in this article also highlight the importance of considering the actual vehicle transverse position in the evaluation of existing bridges.

Recent years has witnessed a steady increase in the issued overweight vehicle permits. Damage and deterioration of bridges caused by overweight vehicles have received increasing attention. Most previous studies on overweight vehicles have focused on the routing and weight regulation of overweight trucks while little attention has been paid to the determination of the optimal transverse position for overweight trucks to cross highway bridges. This article aims to investigate the optimal transverse position for overweight trucks to cross the simply supported multi-girder bridges and provide suggestions for the management of overweight vehicles. Finite element analysis is performed for a group of prefabricated concrete bridges commonly used in China under the action of overweight trucks with varying transverse positions, and the optimal transverse position is determined based on the maximum bending stress of the girders. The effects of a few important factors, including the superstructure configuration, length of bridge spans, number of girders, type of girder connections, and support conditions, on the optimal transverse truck position are also investigated. The findings in this article highlight the importance of the transverse position of overweight trucks when crossing multi-girder bridges.