Stochastic Modeling of Ground Motions Matching Spectral Acceleration, Cumulative Arias Intensity and Duration

Abstract eng:
In performance-based earthquake engineering, a large number of ground-motion time histories are needed for analyzing the distribution of dynamic response of nonlinear systems. In current design practice, ground motion effects on structures are represented by an elastic response spectrum, yet the response spectrum doesn’t contain other important ground-motion features such as energy build-up, duration as well as ground-motion nonstationarity, which are found to be important in the analysis of certain types of structures. In this study, a stochastic ground-motion simulation and modification technique is developed to generate energy-compatible and spectrum-compatible (ECSC) synthetic motions through wavelet-packet characterization and modification. The ECSC method significantly advances traditional ground-motion modification approaches, because it generates ground motions that not only match target spectral accelerations, but also match other important parameters such the Arias intensity, its temporal accumulation, as well as measures of ground-motion duration. A salient feature of the ECSC method is that ground motions are modified in both frequency and time domain iteratively. The great similarity between the ECSC simulated motions and the actual recorded motions is demonstrated through one-to-one comparison of a variety of intensity measures. Furthermore, nonlinear structural responses subjected to the ECSC ground motions and their recorded counterparts are compared using a 12-story reinforced concrete perimeter frame model. The numerical analyses demonstrated that the NGA and ECSC ground motions result in very consistent structural responses. The ECSC method can be easily implemented in the generalized conditional intensity measure (GCIM) framework to directly simulate a set of motions following a targeted distribution of multiple intensity measures. The simulation can be repeated for many realizations such that a collection of the simulated motions will follow the targeted distribution of spectral accelerations, duration and Arias intensity for a specific earthquake scenario. Therefore, the ECSC method has great potential to be used in performance-based earthquake design and analysis.

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