Assessment of local damages in box-girder bridges using measured dynamic responses by passing vehicle

Highway bridges are subjected to the dynamic tire forces of moving vehicles. This paper attempts to identify local damages in box-girder highway bridges from the dynamic responses induced by passing vehicle. The box-girder bridge is modeled using four-node iso-parametric flat shell element taking into account the transverse shearing deformation in the finite element model. The vehicle is modeled as a two degree-of-freedom system. The local damage is simulated by a reduction in the elemental Young´s modulus. In the forward analysis, a coupled bridge-vehicle system is built using the finite element analysis. In the inverse analysis, a dynamic response sensitivity-based finite element model updating approach is used to identify local damage in the element level. The solution is obtained iteratively with the penalty function method with regularization from the measured structural dynamic responses. A single-span box-girder bridge is studied as a numerical example. The effects measurement noise and measurement time duration on the identification results are investigated. Studies in this paper indicate that the proposed method is efficient and robust for local damages identification and good identified results can be obtained from the time histories of several measurement points.