Random Vibration Theory Based Seismic Site Response Analysis

Abstract eng:
In this paper, an alternative approach for seismic site response analysis is presented. This approach is based on Random Vibration Theory (RVT) and works in frequency domain. With this approach, the need for time history generation is eliminated and the responses are computed at the selected confidence level. This approach follows the SHAKE theoretical framework and is based on closed form solution of one-dimensional wave propagation. The main difference with the commonly used approach in the program SHAKE are as follows: • • • • The calculation starts by computing the power spectral density (PSD) function of the design acceleration response spectrum. Following the computation of frequency domain transfer function for the repose of the interest, the PSD of the response is obtained. The peak factors for the PSD responses are computed and the statistical means of the maximum responses are computed. The maximum shear strain in each soil layer is used to iterate on soil properties using the strain-dependent soil properties of each layer based on the equivalent linear method until convergence is reached for all soil layers. After the final iteration on soil properties, the maximum responses of interest such as acceleration response spectra, peak shear stress and strains are obtained. This approach does not require time history as input and the design response spectra can be used directly in the analysis. This approach has been implemented in a new computer program named P-SHAKE and has been used successfully in recent projects. This paper provides the theoretical basis of the approach and presents a comparison of the P-SHAKE and SHAKE results and describes the advantages and limitations of the new method.

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