Nowadays, seismic codes are regularly updated with new knowledge and a better understanding of the earthquake phenomenon. With these updates, existing buildings require a reevaluation of their stability and a process of reinforcement and/or retrofitting. This study investigated the effects of two types of ground improvement which use cement-mixing soil surrounding the foundation structure to reduce and redistribute forces acting on piles. This is especially important when the reevaluation of high-rise buildings leads to increased forces in the piles. Typically, buildings are designed while assuming fixed base boundary conditions at the foundation level, without considering soil–pile–structure interaction (SPSI). SPSI significantly influences the response of high-rise buildings supported by soft soil. Increasing the lateral resistance of the surrounding soil can reduce the influence of SPSI. In this study, a detailed dynamic numerical analysis was used to investigate the dynamic response of an SPSI system of a high-rise building under seismic load. A dynamic analysis was conducted on a modified layout of a real building, using real-time earthquake motion. The finite element program DIANA FEA was used to perform nonlinear 3D FEM numerical simulations, taking into account the essential SPSI phenomena, gap-slip between the piles and the soil, and free-field boundary conditions. A comparison of the data suggests that the bending moment and shear forces in the piles are reduced in magnitude and evenly distributed along the upper part of the pile, which reduces the stress concentration of the bending moment and shear forces at the contact between the piles and the pile cap.

This study presents the numerical simulation of flexible wall barrel soil-pile-structure interaction analysis. Soil-Structure Interaction (SSI) is usually assumed beneficial during an earthquake. However, SSI can also increase permanent deformation and decrease the stiffness of the pile foundation system which affects seismic response and displacement in the overall structure, especially high-rise buildings. Non-linear 3D FEM models with a gap/slap mechanism have been developed in ABAQUS to simulate the effect of soil-pile-structure interaction (SPSI). The objectives of this research are to study the effect of SPSI on soil response, kinematic properties of the superstructure, and the modeling of SPSI problem with the superstructure, and to increase horizontal stiffness of foundation system by using the cement-mixing method. The analyses in this study include superstructure analysis with fix-based, SPSI, and SPSI with cement-mixing. The constitutive models in this study are Mohr-Coulomb for soil material and Linear-elastic for the upper structure. The calibration of the flexible wall barrel modeling technique was successfully calibrated with a shaking table reference case with some variation of the results. It is observed that SPSI provides flexibility and damping to the superstructure. The gap/slap mechanism is clearly observed on the contact surfaces between soil and superstructure at a shallow level. Cement-mixing soil improvement increases horizontal stiffness resulting in a stiffer response of superstructure and reduction of pile stress during earthquakes. The influence of SPSI on superstructure and comparisons between simulation cases are then discussed. However, this study does not consider consolidation and the contraction properties have been simplified.