Seismic performance evaluation of underground structures using endurance time analysis

The endurance time analysis (ETA) is an efficient seismic performance evaluation method characterized by developing series of seismic response compatible acceleration time histories whose amplitudes increase with the duration. The artificial endurance acceleration time histories are used as the input for engineering structures to perform nonlinear dynamic analyses. ETA can effectively capture the entire dynamic response of the structure from elastic to plastic till finally collapse, and can be used as an alternative approach to evaluate the seismic performance of structures. In order to study the applicability of this method in the seismic performance evaluation of underground structures, the Dakai subway station is taken as the prototype, and a two-dimensional finite element model considering soil-structure interaction is established. Three endurance time acceleration functions (ETAFs) are generated based on the design response spectra of Chinese seismic design code. The seismic response characteristics of the Dakai subway station subjected to three ETAFs and 15 real ground motions are compared in this study. The numerical results show that the responses of ETA generally fall between the envelopes of incremental dynamic analyses (IDA) using the real ground motions. The average response of the subway station using ETA is also in good agreement with the average results using IDA. Therefore, ETA provides a new computationally efficient alternative for seismic performance evaluation of the underground structures other than the traditional nonlinear IDA. Besides, the response spectrum corresponding to the fundamental period of the soil-structure interaction system is more preferable than the peak ground acceleration as the seismic intensity measure for the performance evaluation of the underground structures.