STUDY ON THE INFLUENCE OF FOUNDATION STIFFNESS ON THE SEISMIC PERFORMANCE OF HIGH-RISE BUILDINGS

A structural analysis model, which considers the influence of both the pile foundation stiffness and the restraint provided by the soil around the basement, is established in this paper. The associated principles of determining the vertical stiffness of pile, as well as the method of calculating the stiffness of the springs for the soil around the basement, are proposed. Through the time-history analyses of three shear wall structures with different stories (i.e., 21, 32 and 43) under 7 ground motions, the effects of foundation stiffness and soil spring stiffness on the seismic performance of structures are investigated. The results indicate that if the foundation stiffness is taken into consideration, the vibration periods and the inter-story drift ratios of the structure increase, while the horizontal shear forces and overturning moments slightly decrease. The reaction force acting on the exterior basement external walls provided by the soil significantly increases, while the amplitude of the variation of the top reaction force for the piles decreases. For the buildings with rectangular plane, the influences of foundation stiffness on the short edge direction are much larger than those on the long edge direction. In addition, the influence of foundation stiffness increases with the increasing of the building height and aspect ratio. Due to the relatively high aspect ratio, the lateral stiffness is generally regarded as the critical control factor for tall building. Hence, the influence of foundation stiffness on the seismic performance of structures requires further attention.