Application of Endurance Time Method for the Seismic Assessment of an Isolated Viaduct

Endurance Time (ET) method is a dynamic analysis in which the structures are subjected to a predefined intensifying acceleration. The inherently dynamic nature of ET makes it applicable for various types of structures with different heights and degrees of freedom. The purpose of this study is to investigate the feasibility of ET method for analyzing an isolated bridge under different controlled systems. The optimal control force is calculated using both the Linear Quadratic Regulator (LQR) algorithm and Continuous Sliding Mode Control (CSMC). To this end, a five-span isolated viaduct is selected as a case study. Column-isolator-deck system is idealized as a two-degree-of-freedom lumped mass model. Three distinct control strategies are used including active, semi-active, and passive control systems. The deck displacements obtained from ET method are compared against the results of conventional time history analysis for different excitation levels. The ET results show good accuracy in predicting the seismic behavior of isolated bridge under different controlled systems. On top of that, this method substantially reduces the computational demands contrary to time history analysis.