Seismic performance assessment of tunnel form concrete structures under earthquake sequences using endurance time analysis

Abstract

A low-computational cost method is developed for seismic performance assessment of tunnel-form concrete structures under earthquake sequences. Using incremental dynamic analysis (IDA), a structure already damaged under a code spectrum-compatible mainshock is subjected to a set of aftershock events. The seismic reliability of the structure under successive earthquakes is then evaluated by comparing the fragility curves of the intact and the damaged structures. To achieve this, the newly developed endurance time approach is used to obtain the residual capacity of the structures to withstand aftershocks. The efficiency of the proposed method is demonstrated by using 5 and 10-storey 3D tunnel-form concrete structures as case study examples. It is shown that using endurance time method for seismic performance evaluation under mainshock-aftershock sequences generally leads to accurate results (less than 15% error), while it can significantly reduce (up to 90%) the computational costs of the conventional IDA method. The results also indicate that the application of the code design basis earthquake as the mainshock has no significant effect on the seismic performance of the tunnel form concrete structures under aftershocks, especially for the shorter systems. This highlights the excellent seismic resistance of tunnel-form structures under earthquake sequences.