Bridge rating modification to incorporate fatigue damage from truck overloads

Abstract

As the number of requests for permits to use bridges by heavy trucks increases, there is a concern over the potential for rapid fatigue damage to the affected bridges. The damage may especially become critical for bridges that have been designed for lower truck loads than those currently used in practice. To limit damage, and to indirectly impose a cap on the number of overload permits, a modification factor in the bridge rating equation to incorporate the fatigue damage potentials from overloads is introduced. This factor is derived based on the amount of damage that a specific overload may cause and is found to be mainly affected by the current bridge age and the percentage of overloads in the entire truck load population. For single and continuous span steel girder bridges with welded cover plates, simple forms of this modified equation have been proposed and introduced in the paper.