NEAR-FAULT GROUND MOTIONS WITH PROMINENT ACCELERATION PULSES PART 1: EVALUATION OF PULSE CHARACTERISTICS AND THE STRUCTURAL DAMAGE POTENTIAL

Recent major earthquakes (Northridge 1994, Kobe 1995 and Chi-chi 1999, etc.) have shown that many near-fault ground motions possess prominent acceleration pulses. Some of the prominent ground acceleration pulses are related to the large ground velocity pulses, others are caused by mechanisms that are totally different from those causing the velocity pulses or fling steps. Various efforts to model accelerat ion pulses have been reported in the literature. In this paper, we summarize some research results from our recent study of acceleration pulse prominent ground motions and analysis of acceleration pulse induced structural damage effects: (1). Temporal characteristics of acceleration pulses (2). Ductility demand spectrum of simple acceleration pulses with respect to equivalent classes of dynamic systems and pulse characteristic parameters (3). Estimation of fundamental period change under the excitation of strong acceleration pulses. By using the acceleration pulse induced linear acceleration spectrum and the ductility demand spectrum, a simple procedure has been developed to estimate the ductility demand and the fundamental period change of an RC structure under the impact of a strong acceleration pulse