Integrated High‐Fidelity Soil–Structure‐Interaction Analysis of a Tall Reinforced Concrete Core Wall Building

This paper evaluates the influence of soil–structure interaction (SSI) on the seismic performance of a 25‐story reinforced concrete core wall building designed under performance‐based seismic design (PBSD) guidelines. A high‐fidelity three‐dimensional nonlinear finite element model was developed in OpenSees to capture nonlinear soil and superstructure behavior and explicit interaction among the superstructure, foundation, and surrounding soil. Nonlinear response‐history analyses were conducted for both the SSI model and a conventional fixed‐base superstructure model. Engineering demand parameters, including interstory drifts, floor accelerations, coupling beam rotations, wall strains, and core wall shear and moment demands, were compared to assess SSI effects. Results show that the two models produce broadly consistent predictions of seismic demands above ground level. The SSI model predicted up to 50% smaller shear force in basement walls due to interaction between the basement walls and surrounding soil. SSI primarily reduced short‐period floor acceleration spectra (<0.5 s) at the floor center of mass and localized demands at the ground level, where shear and moment responses in the reinforced concrete (RC) core differed by up to 10%. Moment demands imposed on the foundation were also reduced in the SSI model by up to approximately 10% and 20% beneath the RC core and basement walls, respectively. This relatively limited SSI influence is mainly attributed to the site's stiff conditions, where excavation of about 20 m of softer soils left a dense coarse‐grained layer ( V s ≈ 480 m/s) over bedrock at 30 m depth, resulting in a short site period and limited soil–foundation compliance. These findings indicate that fixed‐base modeling remains adequate for PBSD on shallow, relatively stiff soil sites, though SSI may warrant explicit consideration for low‐ to mid‐rise buildings, deeper or softer soil profiles, or design checks at or below ground level.