Innovative method to simulate design earthquake motions by controllingearthquake motion phase and proposal of new performancedesign criterion

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Both the amplitude and phase characteristics of earthquake motion provide key information needed to evaluate the aseismic capacity of designed structures. In this research we proposed a simple method for modeling the phase characteristic of earthquake motion based on group delay time (the first order derivative of an earthquake motion phase with respect to the circular frequency) and wavelet analysis. Existing data sets of observed earthquake motions and wavelet analysis are used to calculate the group delay time of each earthquake motion. Regression equations for the mean group delay time and standard deviation of group delay time in each frequency band defined in the used wavelet are obtained as functions of the earthquake's magnitude and several source parameters, hypocenter distance as well as local soil conditions. After confirming that the uncertainty of the group delay time could be expressed by the normal distribution, we developed a simulation method of group delay time. To re … More duce complexity of this method we also developed a method to simulate the group delay time based on a first order of the stochastic differential equation. A sample phase spectrum was obtained by integrating a sample group delay time with respect to the circular frequency.Using the sample phase spectrum an earthquake motion compatible with the elastic design response spectrum is then simulated, and its characteristic is investigated using the yield strength demand spectrum. Through this investigation we found that the yield strength demand spectrum was strongly affected by the phase spectrum used for an analysis. If we used a different sample phase spectrum a different yield strength demand spectrum produced even though its elastic response spectrum satisfies the same design elastic response spectrum. To solve this problem we therefore proposed a method to simulate a unique design earthquake motion, which is simultaneously compatible with both the given elastic response spectrum and the yield strength demand spectrum.We also developed a method to simulate realistic earthquake motions using only the information of a phase spectrum taking into account the causality criterion of earthquake motions. Less