Dynamic Stiffness Identification of Portal Frame Bridge–Soil System using Controlled Dynamic Testing

Abstract

Short-span portal frame bridges are predominant in Swedish railway lines. Although it is well known that the dynamic response of these partially-buried rigid structures is governed by the surrounding soil, the effect of the soil is usually neglected in the train-induced vibration analysis due to the expensive computational costs. This paper focuses on studying the effect of the surrounding soil conditions on the dynamic response of portal frame railway bridges. The study aims to validate the accuracy of simplified numerical models in evaluating the dynamic stiffness and modal properties of the bridge–soil system. To achieve this aim, a model updating method was used for FE model calibration of a full–scale portal frame bridge using measured frequency response functions. Both measured and computed responses identify the substantial contribution of the surrounding soil on the global damping of the system and highlight the importance of the soil–structure interaction on the dynamic response of these structures.