Effects of Pile Group Configuration on the Seismic Response of Buildings Considering Soil-Pile-Structure Interaction

Abstract

Mid-rise buildings supported by different configurations of end-bearing pile foundations can fulfil the design requirements addressed in the modern building codes and selecting the most efficient configuration is a challenging task. In this study, the influence of group configuration (but keep the area replacement ratio constant) on the seismic response of mid-rise buildings resting on end-bearing pile foundations considering seismic soil-pile-structure interaction (SSPSI) is investigated. A soil-pile-structure system is simulated in FLAC3D to carry out the fully nonlinear seismic analysis in the time domain. The elastic-perfectly plastic structural behaviour is considered while the variation of soil shear modulus due to cyclic shear strain and the corresponding damping ratio is simulated adopting hysteretic damping algorithm, and the soil plastic behaviour is modelled using Mohr-Coulomb criterion. The results of the seismic pile responses, namely the envelopes of shear forces and bending moments along the piles and the lateral pile displacements, and the building responses including the base shear, and the lateral building displacements are reported and discussed. It is observed that for the cases analysed, the pile group configuration influences the seismic response of the system. Provided that the same volume of concrete (i.e. constant area replacement ratio) is used for all cases, by increasing the number of piles but with smaller diameters, more seismic loads may be attracted to the system due to the kinematic interaction between the piles and the surrounding soil and consequently causing the increase in the base shear and lateral displacements of the building.