Identification Of System Parameters And Analysis Of Seismic Response Considering Soil-Structure Dynamic Interaction

In this thesis, the study methods about SSDI (soil-structure dynamic interaction) are reviewed systemically. The field of SSDI is very important to civil engineering because of its complex study contents and much calculating methods. Though this field has been studied for several tens years, there are still some problems in the SSDI, such as, how to found soil foundation lumped parameters model about actual site, how to simulate the contact problem between soil and pile, how to identify the structural natural oscillation properties after considering soil-structure interaction in time domain, etc. There are four parts in the dissertation for Ph.D.In the first part, a forth-order staggered-grid finite difference approach is used to compute the seismic response of three-dimensional shallow site and the corresponding Fortran computing program is developed. This is a new method to analyze dynamic response of three-dimensional free-field site.In the second part, the identification of structural natural oscillation properties after considering soil-structure dynamic interaction is studied. Most of identification methods is only used in frequency domain in civil engineering now, the identification method in frequency domain will bring much deficiency, such as, some information of data will be lost when the recorded data in time domain is transformed to frequency domain, and the processing of transfer function will bring much errors. In the paper, the ARX (Auto-Regressive Exogenous) parameters model in time domain is used to identify the structural natural oscillation properties based on the seismic recorded data and a simple and effective way is offered to determine the order of ARX model parameters. The structural natural oscillation properties after considering the soil-structure dynamic interaction are identified using the ARX model.In third part, the parameters values of all types of soil foundation lumped parameters models are obtained by basing on uniform elastic half-space site, it may be bring much errors if these lumped parameters model is used to replace the actual soil foundation because the actual soil is heterogeneity, anisotropic and non-linear. In the paper, both damping least square method and modified EKF(Extend Kalman Filter) identification method are offered to resolve the problem how to found lumped parameters model in actual complex soil foundation. The modified EKF identification method can also be used to structure monitoring problems.In the forth part, soil-pile-structure interaction is studied. A modified Goodman contact element is offered in the paper to reduce the deficiency of original Goodman contact element. A finite element program in Fortran is developed and soil non-linear problem is considered using the Seed's equivalent linearization method. Some different examples are computed using the modified Goodman contact element.In summary, the contents and conclusions of the paper are including:1. The seismic response of free field is studied. The seismic response of one-dimensional site is computed using the second order finite difference method to simulate the earthquake wave propagating in free field. A three-dimensional free-field is analyzed here. The FDM (Finite Difference Method) program in FORTRAN is developed in the paper and the program offer a new way to analyze the free-field site seismic response.2. The identification of structural low order modal shape after considering soil-structure dynamic interaction is studied. The ARX parameters model is used and the identification program in Matlab is developed using the ARX model. Using the program, an actual structural oscillation properties in Alaska is identified according to the actual earthquake records. The identified results are compared with the results obtained in frequency domain. The compared results shows that this identification method has more identification precision and be easy to operate.3. The varied damping least square method is offered in the paper. The parameters of soil foundation two-degree-of-freedom lamped parameter model are identified by using this back analysis method and the corresponding program in FORTRAN is made in the paper.4. A modified EKF (Extend Kalman Filter) method is offered to identify the parameters in soil foundation two-degree-of-freedom lamped parameter model. The identified results obtained by the modified EKF are more credible. A iterative program in Matlab is developed to resolve the problem which the identified results are strongly depended on the original system model values.5. A new contact model of soil-pile interaction is offered in the paper based on the Goodman...