On the Influence of Earthquakes and Soil Characteristics on the Seismic Response and the Performance of Isolated Bridges

Abstract

AbstractSeismic isolation technology is an effective mean of reducing seismic risk and enhancing the structural seismic performance. However, some parameters affect and mitigate the efficiency of this technology: earthquake inputs and soil characteristics. The main purpose of this study is to investigate the simultaneous effects of different records and flexible soils on isolated bridges. For this reason, an isolated bridge is assumed to be at different distances from the ruptured fault (Rrup) to represent the near-fault (NF) and far-field (FF) situations. These records are extracted on different soils which are categorized based on their shear velocity to represent different soils’ behaviors and characteristics. Nonlinear time history analyses (NTHAs) are carried out on a typical isolated bridge model with the SAP2000 software. Responses in terms of deck acceleration, base shear, displacement and the performance of the isolation units are studied. Results demonstrate that for NF zones, the consideration of the soil effects is imperative. In soft soils, all seismic responses are amplified, leading to higher force and displacement demands. In such zones, not considering this fact during the design, results in largely insufficient displacement and force capacities of the isolated bridge system are seriously harming its seismic performance.KeywordsSeismic isolationEarthquake characteristicsNear-faultFar-fieldSoil effectsSeismic responseBridges