Effects of soil-structure interaction on seismic response and damage of isolated structures

Based on the Winkler foundation theory and wave theory, the dynamic impedance of group soil-pile to the upper structure is calculated, and the effects of soil-structure interaction (SSI) on structural responses and non-linear damage of isolated high-rise structures is studied. The horizontal stiffness coefficient of foundation around pile is calculated first, then by equivalence of group piles to single pile using an improved Penzien model, the horizontal stiffness coefficient of top pile is calculated with consideration of certain length of pile. According to the magnitude of structural vibration frequency and basic frequency, the influence of the material damping and radiated damping is considered. In case of an isolated building, the dynamic impedance is calculated according to the actual arrangement of group piles and conditions of soil layer, and the seismic responses of the building is calculated by using the equivalent linear model of the structure and the response spectrum method. The effects of SSI on an isolated structure are discussed, and the effects of SSI on the damage of structural main members are calculated using non-linear seismic response analysis. Analysis results indicate that effect of SSI decreases with the increase of the story number. The displacement of isolation layer and pressure of bearing are increased by considering the effect of SSI, and there is no effect on story drifts of super structure. The damage of coupling beam is decreased, while the damage of column and shear wall is more serious by considering the effect of SSI. The effect of SSI is increased when the structure is subjected to long period earthquake motion.