Parametric analyses of dynamic interaction between three-dimensional soil and frame structure group under earthquake loadings

Dynamic interaction between soil and structure group (SSGI) is of great significance to the seismic design and evaluation of structures in densely built areas. However, detailed three-dimensional parametric analysis of the SSGI effect using realistic modeling on both the superstructure and soil is still limited. This study develops a three-dimensional numerical method to account for the SSGI effect and validates it against the shaking table test result. Subsequently, parametric analyses are conducted to investigate the SSGI effect for a three-dimensional soil and structure group, where key parameters include the structure height, number, and spacing, material properties of the soil, and spectrum distributions of seismic records. Compared with the dynamic interaction between soil and a single structure, the SSGI can reduce the structural base shear and story drift (up to 17% and 24%, respectively) in most cases. However, the level of reduction is below 5% when (1) structure spacing is greater than 2.0 times the width of the structure foundation or (2) the shear wave velocity of soil is no less than 300 m/s. Essentially, the SSGI changes the seismic demand of the concerned structure mainly by altering its local ground acceleration input at the base. The SSGI effect is more significant when structure spacing is reduced, structure number is increased, or the height of the central structure equals those of the surrounding structures. In contrast, the influence of soil property on the SSGI effect is minor under medium-level earthquakes.