Effect of the soil-structure interaction in the seismic response of a structural archetype with a combined system

Abstract

Soil-structure interaction (SSI) can significantly modify the seismic response of buildings; however, in structural design practice it is common to assume an idealized fixed-base condition. This study evaluates the effect of SSI on the seismic response of a structural archetype with a combined system of reinforced concrete frames and shear walls, designed with moderate energy dissipation capacity (MED). Three numerical models were developed: a fixed-base model and two flexible-base models that incorporate SSI through a foundation slab and a pile foundation system, respectively. The structural response was evaluated using modal response spectrum analysis and nonlinear static (pushover) analysis, considering variations in soil stiffness and structural adjustments associated with seismic demand. The results show that the inclusion of SSI increases the fundamental vibration periods and interstory drifts, with more pronounced effects in the pile foundation system. In addition, significant redistributions of axial loads and reductions in global ductility were observed, particularly in the case of deep foundations. These findings indicate that the fixed-base assumption does not always lead to conservative estimates and highlight the importance of explicitly considering SSI in the analysis and design of buildings with combined structural systems.