Dynamic Analysis of Vertical and Horizontal Irregular Reinforced Concrete Structure Considering Soil Structure Interaction

Abstract

Numerous studies have examined soil-structure interaction (SSI) effects on the seismic response of high-rise buildings, comparing them to fixed-base models. These investigations have integrated SSI into dynamic analyses and highlighted key provisions in major seismic codes. However, most research focuses on regular structures with uniform mass, stiffness, and strength distribution, while only a few addresses geometric irregularities. (Stewart, 2012 & J-Priyadarshini, 2013). This study employs ROBOT Structural Analysis 2019 to numerically model an irregular 8-storey reinforced concrete structure (with horizontal and vertical irregularities) under seismic loading, considering SSI and comparing its response to that of a regular structure. The soil is modeled as a homogeneous, linearly elastic medium using spring elements. Four dynamic analyses are performed: one with a fixed base and three incorporating SSI for different soil types per the Algerian Seismic Code (RPA 2024) . These analysis results are compared with those of the fixed-base structure. The findings indicate that the effect of the ISS on the dynamic modal response (particularly the fundamental period) grows with soil flexibility and becomes even more pronounced in irregularly shaped structures. Thus, both structural irregularity and the flexibility of soil amplify the ISS’s impact on dynamic behavior. Regarding seismic response, fixed-base assumptions lead to overestimated internal forces in walls and columns for all building types, while relative displacements are underestimated in regular buildings and show a more significant increase in irregular ones. The results demonstrate that soil-structure interaction significantly affects the seismic performance of buildings, particularly those with irregular geometry