Near-fault ground motions, and the response of elastic and inelastic single-degree-of-freedom (SDOF) systems

In order to investigate the response of structures to near-fault seismic excitations, the ground motion input should be properly characterized and parameterized in terms of simple, yet accurate and reliable, mathematical models whose input parameters have a clear physical interpretation and scale, to the extent possible, with earthquake magnitude. Such a mathematical model for the representation of the coherent (long-period) ground motion components has been proposed by the authors in a previous study and is being exploited in this article for the investigation of the elastic and inelastic response of the single-degree-of-freedom (SDOF) system to near-fault seismic excitations. A parametric analysis of the dynamic response of the SDOF system as a function of the input parameters of the mathematical model is performed to gain insight regarding the near-fault ground motion characteristics that significantly affect the elastic and inelastic structural performance. A parameter of the mathematical representation of near-fault motions, referred to as 'pulse duration' (T-p), emerges as a key parameter of the problem under investigation. Specifically, T-p is employed to normalize the elastic and inelastic response spectra of actual near-fault strong ground motion records. Such normalization makes feasible the specification of design spectra and reduction factors appropriate for near-fault ground motions. The 'pulse duration' (T-p) is related to an important parameter of the rupture process referred to as 'rise time' (tau) which is controlled by the dimension of the sub-events that compose the mainshock. Copyright (C) 2004 John Wiley Sons, Ltd.