Parameter identification and nonlinear earthquake response analysis of soil-structure interaction system

Abstract

This dissertation presents a systematic procedure for the earthquake response analysis of a soil-structure interaction system incorporating the identification of the system stiffness parameters based on forced vibration test (FVT) data. This study is in conjunction with the Hualien large-scale seismic test structure that was recently built in Taiwan for international joint research. The parameters identified are the shear moduli of several sub-domains of the near-field soil regions as well as the Young````s moduli of the shell sections of the structure. The soil-structure interaction system is modeled by the finite element method combined with the infinite element formulation for an unbounded layered soil medium. Preliminary investigations are carried out on both the results of the static stress analysis for the soil medium and the results of the in-situ tests in order to divide the soil-structure system into several regions with homogeneous properties and to determine the lower and upper bounds of the parameters for the purpose of identification. Then two sets of parameters are identified for two principal directions based on the forced vibration tests by minimizing the estimation error using the constrained steepest descent method. The simulated responses for the forced vibration tests using the identified parameters show excellent agreement with the test data. Utilizing the identified soil properties as the initial linear values, earthquake responses are predicted for the measured earthquakes using the equivalent linearization technique based on the strain dependent characteristics of the shear moduli and damping ratios. The earthquake responses are analyzed by using the substructured wave input technique. Three components of ground acceleration time histories are artificially generated through an averaging process of the Fourier amplitude spectra of ground accelerations measured near the test structure and they are used as the control motions for earthquake...