Nonstationary ground motion model and applications to analysis and design of earthquake-resistant structures

To account for the uncertainties that are inherent in the definition of earthquake ground motions, this investigation is carried out in a probabilistic framework. A new, versatile, stochastic earthquake ground motion model is developed to represent the multifold characteristics of actual earthquake ground motions. This earthquake model is formulated in continuous-time and can also be extended in discrete-time; therefore, it is usable for both analytical random vibration and Monte Carlo simulation studies of structural response. An existing nonparametric adaptive method is extended to estimate the temporal variation of the intensity and frequency content of real earthquake ground motions. The nonlinear least square identification technique is used to calibrate the earthquake model against real earthquake records. Explicit closed-form solutions are derived for the time-varying power spectral density functions and nonstationary correlation functions of the response of linear elastic multi-degree-of-freedom systems subjected to this new earthquake excitation model. Monte Carlo simulation studies are conducted to gain insight into the effects of earthquake ground motion nonstationarities on linear and nonlinear structural response. The effects of the frequency nonstationarity of earthquake ground motions on the inelastic response and related damage of structures is examined. The long-term goal of this research is to improve the reliability of seismic codes for the design of safer and more economical structures