Quantifying near-fault impulsive effect on inelastic displacement ratios of self-centering SDOF systems using spectral-equivalent ground motions

Self-centering structures, which aim at minimizing post-earthquake residual deformations, have drawn increasing attention. Near-fault ground motions are known for their impulsive characteristics and may impose high seismic demands on self-centering structures compared to ordinary ground motions. This study investigates the near-fault impulsive effect on inelastic displacement ratios (C_R, i.e., inelastic to elastic peak displacement ratio) of self-centering single-degree-of-freedom (SDOF) systems by developing the impulsive amplification ratio (A_p) spectra. First, the near-fault impulsive effect is quantified in isolation from the effect of elastic spectral shape by using spectral-equivalent pulse-like and ordinary ground motions. Constant-strength spectral analyses are conducted to develop the A_p spectra. Then, the probabilistic characteristics of A_p are analyzed, and systematic lognormality tests are conducted to evaluate the effectiveness of the lognormal distribution model for representing the probabilistic characteristics of A_p. The results show that the A_p spectra exhibit a complex multi-peak shape with strong dependence on the normalized period (T/T_p) and the hysteretic parameters of self-centering SDOF systems. Moreover, the lognormal distribution model can properly represent the probabilistic characteristics of the A_p index with superior robustness over variant combinations of the hysteretic parameters of self-centering SDOF systems. Finally, the probabilistic prediction model for the A_p spectra is proposed using artificial neural network techniques, and the sufficiency of the model for assessing the near-fault impulsive effect under various probability levels is confirmed.