Estimation of response of skewed bridges considering pounding and supporting soil

Abstract Skewed bridges are prone to large in-plane rotations of the girders, especially when seismically-induced pounding with the abutments occur. These rotations have been associated with increase in relative displacements, leading to potential unseating or permanent dislocation of the girders, especially in the transverse direction. The approach adopted in current design specifications for the seat lengths of skewed bridges is oversimplified and could potentially underestimate the relative displacements. Shake table tests were performed on a 1:20 scale bridge-abutment model with 0° (straight), 30°, and 45° skew angles. The effects of pounding, supporting soil, and ground motions simulated based on different soil conditions were considered. The bridge segment and abutments experienced spatially uniform excitations. The results were used to develop empirical formulae for estimation of the relative displacements of skewed bridges. Normalisation of the responses means that the proposed approach can be incorporated into design specifications – as an amplification or reduction compared to that calculated for a straight bridge. It was found that the empirical formulae proposed in this study are able to provide more conservative estimates of the expected relative displacements of the girders of skewed bridges.