Influence of ground motion characteristics on seismic response of skewed bridges

Abstract

Abstract Skewed bridges are bridges with longitudinal axes at an angle to the abutments. They are more susceptible to damage during seismic events due to in-plane rotations of the girders induced, especially when pounding occurs. Most current design standards do not consider many factors that could significantly affect the response of skewed bridges, such as the skew angle and effect of the supporting soil. A bridge-abutment model with 0°, 30°, and 45° skew angles were subjected to shake table tests. Ground motions were simulated based on the New Zealand design spectra for Class C and E soil conditions. The effects of the different characteristics of ground motions on the seismic response of skewed bridges considering presence of pounding and the supporting soil were investigated. The results were also used to evaluate the recommendation of girder seat lengths specified in design specifications, e.g. the New Zealand Transport Agency (NZTA) Bridge Manual. It was found that the NZTA recommendation for seat length could potentially significantly underestimate the out-of-plane movements of the girders. In the worst case, the displacement of the skewed bridge was up to 3.48 times that of the straight bridge – much larger than the recommended value of 1.25 times.