Studies On Seismic Performance Evaluation Of Structure-foundation-ground Interaction

Soil-structure interaction is not considered in most of present structure seismicdesign and analysis. But studies have showed that soil-structure interaction hassignificant influence on seismic response of structure. Normally, it can prolong thefundamental period and enlarge the top displacement of structures. In recent years，capacity spectrum method which has aroused many scholars，interests, is a method ofperformance-based seismic design, but it is mainly based on the assumption of rigidfoundation. Capacity spectrum method considering soil-structure interaction is studiedin the paper.The soil-structure interaction is applied to the capacity spectrum method to obtainthe performance point of structure, which is divided to flexible foundation effects,kinematic effects and foundation damping effects according to FEMA440. Firstly, thepaper makes a pushover analysis to an eight and a fifteen storey reinforced concreteframe structure models which consider the influence of the soil-structure interactionby using the “m” method to obtain base shear and top displacement curve, and withsome transformation, the curve is transformed into capacity curve of SDOF systemwith spectral displacement and spectral acceleration as horizontal axis and verticalaxis respectively. Secondly, through some amendment considering kinematic effectsand foundation damping effects to initial demand spectrum that are chosen fromstandard spectrum and14real seismic spectrum suitable for Ⅱ,Ⅲ class site, demandspectrum considering soil-structure interaction are obtained. Lastly, performance pointof structure is obtained through the performance point locus method. Performancepoint of structure without consideration of soil-structure interaction and performancepoint just with consideration of flexible foundation effects are also obtained. Byanalyzing their difference, the influence of soil-structure interaction is pointed out.The structure model is analyzed by the nonlinear time-history method, taking14real earthquake motion records as input. And comparison is made from the aspects offloor displacement, storey drift, storey shear and plastic hinge, the results show thatfloor displacement and storey drift which are calculated by the capacity spectrummethod that considering soil-structure interaction are larger than the time-historymethod, and story shear are smaller. The research of this paper could give some suggestions to structure design considering soil-structure interaction and be helpful toexperimental studies in the future.