Nonlinear dynamic analysis is a required step in seismic performance evaluation of many structures. Performing such an analysis requires input ground motions, which are often obtained through simulations, due to the lack of sufficient records representing a given scenario. As seismic ground motions are characterized by time-varying amplitude and frequency content, and the response of nonlinear structures is sensitive to the temporal variations in the seismic energy input, ground motion non-stationarities should be taken into account in simulations. This paper describes a nonparametric approach for modeling and prediction of non-stationary ground motions. Using Relevance Vector Machines, a regression model which takes as input a set of seismic predictors, and produces as output the expected evolutionary power spectral density, conditioned on the predictors. A demonstrative example is presented, where recorded and predicted ground motions are compared in time, frequency, and time-frequency domains. Analysis results indicate reasonable match between the recorded and predicted quantities.

This study mainly addresses the problem of estimating the prior earthquake damage on the response of reinforced concrete structures to future earthquakes. The motivation has arisen from the heavy damages or collapses that occurred in many reinforced concrete structures following two major earthquakes that recently occurred in the Marmara Region, Turkey. The analysis tool employed for this purpose is the package named IDARC2D. Deterioration parameters of IDARC&#039 / s hysteretic model have been calibrated using a search method. In the calibration process experimental data of a total of twenty-two beam and column specimens, tested under constant and variable amplitude displacement histories, has been used. Fine-tuning of deterioration parameters is essential for more realistic predictions about inelastic behavior and structural damage. In order to provide more realistic damage prediction, three ranges of parameters are proposed. Some damage controlling structural parameters have been assessed via a large number of two-dimensional section analyses, inelastic time history and damage analyses of SDOF systems and seismic vulnerability analyses of reinforced concrete buildings. Inelastic time history and damage analyses of numerous SDOF systems have been carried out to determine whether the loading history has an effect on damage and dissipated hysteretic energy. Then this emphasis is directed to the analyses of MDOF systems. In the analyses of the SDOF systems, various forms of constant and variable amplitude inelastic displacement reversals and synthetic ground motions composed of one of the four earthquake records preceded or followed by its modified records acted as a prior or successive earthquake, have been used. The analyses of two five-story R/C buildings have been caried out using synthetic accelerograms comprised of base input provided by the two recorded ground motions. It is shown that both damage progression and cumulative hysteretic energy dissipated along a path seem to depend on the number and amplitude of cycles constituting the path. However, final damage and accumulated hysteretic energy dissipated along a loading path are independent of the ordering of the same number and amplitude cycles along the path. There is a nonlinear relationship between the earthquake excitation intensity and final damage attained in the end. Increase in the acceleration amplitude leads to exponential increase in damage. As the prior earthquake intensity increases the damage from the succeding main earthquake decreases. A definite ground motion acting as prior and successive earthquake causes substantially different amount of damage. Prior earthquake damage does not substantially affect the maximum drift response in future larger earthquakes. A MDOF frame type structure with aprior damage suffers less overall damage in an earthquake in comparison with the one without a prior damage.