The Applicability of Different Earthquake Intensity Measures to the Seismic Vulnerability of a High-Speed Railway Continuous Bridge

Abstract

There are two common intensity measures (IM), i.e., the peak ground acceleration (PGA) and the spectral acceleration (Sa), for earthquake waves. PGA is a simple peak value of wave, while Sa considers more complex spectral characteristics. And it is necessary to identify which one is suitable for evaluating the seismic vulnerability of high-speed railway (HSR) bridges rapidly developed in the world. A finite element model of a (48 + 80 + 48)m continuous girder HSR bridge with track structure was built by OpenSEES software, and was calculated via an incremental dynamic analysis using both PGA and Sa. The seismic fragility curves of bridge and track components were developed by comparing the seismic demand and capacity of components. The comparison results, respectively, using PGA and Sa, show that both PGA and Sa are suitable for evaluating the seismic vulnerability of HSR bridges, and the using of PGA obtains more conservative fragility curves. Those severely nonlinear components, such as the sliding layer and the sliding bearings, etc., do not have constant local natural vibration periods and their seismic responses are not sensitive to the spectral characteristics of earthquakes. The dispersion of engineering demand parameters (EDPs) using PGA is larger or less than that using Sa for those severely nonlinear components. However, the dispersion of EDPs using PGA is always larger than that using Sa for those linear or slightly nonlinear components.