Influence of scour on dynamic impedances of bridge shallow foundations

Many bridges in earthquake-prone countries cross waterways and have foundations in riverbeds, and thus are exposed to flood, which may cause scour and a change of the bridge dynamics. The present study illustrates a modeling strategy for investigating numerically the influence of scour on the dynamic behaviour of bridges with scoured shallow foundations. The proposed strategy is based on the evaluation of the impedance functions of a massless rigid foundation resting on an elastic half-space under increasing depths of scour. The derived impedance functions are used to evaluate the effects of scour on the dynamic behaviour of a Soil-Foundation-Structure system representative of a bridge pier. In particular, the changes in the fundamental vibration period due to scour are investigated. The results of the study can be used for developing vibration-based scour detection techniques and for investigating the seismic response of scoured bridges.