Evaluation of existing prestressed concrete bridges considering the randomness of live load distribution factor due to random vehicle loading position

Abstract

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.