Dynamic Numerical Analysis Of Pile-soil-structure Based On The Soil Soft Support Model

At present, a favorable reduction in structure response is always according to experience or recommendations, which is mostly based on the assumption of rigid foundation in the practical engineering seismic design. But some research shows that the extension of structure period is not always accompanied by smaller structure response, when considering the flexibility participation of pile-soil foundation and one-sided emphasis on SSI advantages can make too large computational errors to meet the needs of engineering design. The qualitative and quantitative analysis for pile-grouped-soil- structure interaction systems can be carried out efficiently with the combination of theory research and shaking table test. It is very helpful and significant for the SSI effect to be applied to practical engineering design and evaluation.This paper introduces the research history and situation about the analysis of pile- soil-structure interacyion system on home and abroad, the analytical methods and main problems to be solved; the simplied pile-soil-structure model and finite element model are summarized, then integral PGSS model based on pile-grouped nonlinear dynamic interaction is given, and the ANSYS units used in this model are simply introduced.The soil soft support model based on pile-grouped effct in layered foundation is focused on and the spring stiffness and damping coefficient of pile-soil and near filed soil-near filed soil are deduced. After that, a simplified plane interaction finite element analysis model of soil-structure is established and nonlinear dynamic time history analysis is performed for this model, and the comparision among linear analysis, nonlinear analysis and fixed base assumption are made. The analysis results and the existing test results are in good agreement.The three dimensional interaction finite element analysis model of soil-pure frame structure and soil-braced frame structure are established. Nonlinear dynamic numerical analysis is performed for these models under different seismic excitation and different conditions of pile-soil. The result shows that under certain ground motion and soil foundation conditions, nonlinear effect of the upper structure can be greater than fixed base assumption, and pile-soil soft support model also influences the weak layer position on upper structure. It is necessary to consider nonlinear dynamic effect of pile-soil-structure interaction system in engineering seismic design.Based on the parameters of the exsiting vibration test model, the corresponding pile-soil-pure frame structure and braced frame structure are established. A comparision between the analytical results of the above models is made. Both the changes of pile size and soil properties have effect on braced-frame-pile-soil interaction system, which is investigated in this part. The particularity of pile foundation can weaken or strengthen some universial characteristics of soil-structure interaction system, and even some new characteristics may emerge.A simplified numerical analysis method of pile-soil-structure dynamic interaction system based on soil soft support model is presented in this study, and by using structural units to solve computational problems in geotechnical engineering, the designers can carry out dynamic time history analysis and seismic evaluation for the superstructure rapidly and efficiently.