This study investigates structure–soil–structure interaction (SSSI) effects on adjacent reinforced concrete buildings through systematic comparison of response spectrum analysis (RSA; Indian standard IS 1893:2016) and time history analysis (THA). Three-dimensional finite-element models of identical three-storey buildings separated by 50 mm were analysed in the SAP2000 software program for non-interaction analysis, soil–structure interaction (SSI) and SSSI scenarios using four Indian earthquake records. Results reveal SSSI causes force redistribution from −7% to +16% compared to SSI analysis, with maximum amplification at interface footings. Settlement increases up to 15.8% under gravity and 10.2% under seismic loading were observed. SSSI/SSI interaction ratios from THA exhibit ground motion-dependent variability (1.022 to 1.110), compared with 1.050 from RSA, indicating frequency-dependent SSSI amplification. RSA provides a reasonable envelope of SSSI force amplification but cannot capture duration-dependent settlement effects. Design recommendations include 15% force amplification for interface footings and increased seismic gaps based on soil conditions.
Singhai et al. (Fri,) studied this question.
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