Reinforced concrete (RC) moment-resisting frames located in liquefaction-prone areas may experience foundation settlements shortly after strong earthquakes, when the structure has already undergone inelastic deformation and residual damage. In current engineering practice, settlement effects are often evaluated assuming an undamaged structural configuration, potentially leading to unconservative post-earthquake assessments. This study investigates the influence of seismic-induced damage on the subsequent settlement response of RC frames through a decoupled sequential analysis framework that preserves the residual mechanical state attained at the end of the earthquake. Two-storey and four-storey, three-bay RC frames representative of modern Strong Column/Weak Beam and older Strong Beam/Weak Column design philosophies are analysed. Seismic damage is first introduced by nonlinear dynamic time-history analyses using spectrum-compatible ground motions. Foundation settlements are then imposed through nonlinear static analyses by prescribing vertical displacements at the supports via compression-only soil–structure interface elements. The results show that global settlement mechanisms, including axial force redistribution and alternative load paths, are primarily governed by structural geometry and settlement profile, and are only marginally affected by prior seismic damage. Conversely, the local response is strongly influenced by the residual seismic state: permanent curvatures and plastic deformations accumulated during the earthquake significantly reduce the available ductility during the settlement phase. The findings highlight the limitations of settlement assessments based on undamaged models and support the adoption of sequential analysis strategies for a reliable post-earthquake evaluation of RC frames.
