The Influence of Soil Flexibility on Structural Seismic Behavior

The dynamic behavior of buildings during earthquakes is deeply influenced by the interactionbetween the structure and the supporting soil. This work investigates the influence of soil-structure interaction(SSI) on the seismic behavior of 3-, 6-, and 9-story reinforced concrete moment-resisting frames designed inaccordance with the Algerian seismic code RPA99 (Version 2003). The numerical analyses are carried out usingthe FLAC2D software, where the soil is modeled as a homogeneous profile with elastic perfectly plasticbehavior, and the structural components remain within the linear elastic domain. Two scenarios are compared: afixed-base model and a flexible-base model that accounts for SSI effects. The frames are subjected to threerecorded ground motions. The comparison is made in terms of spectral acceleration, top lateral displacements,and base shear. The results indicate that SSI modifies the dynamic response of structures and can induceresonance effects that amplify structural response, highlighting the necessity of considering these phenomena inseismic design.