Impacts of structural and soil parameters on the seismic response of neighbouring buildings: a numerical investigation

This paper presents a numerical investigation of structure-soil-structure interaction (SSSI) effects on the seismic performance of adjacent buildings. Unlike previous studies that focused primarily on small-scale experimental models or limited parametric ranges, the present work introduces three novel aspects: (i) evaluation of SSSI effects at farther normalized building distances (d/a = 4 and 5) beyond those previously tested, (ii) quantification of seismic response changes due to asymmetric building orientations, and (iii) comparison of box versus equivalent pipe column cross-sections under identical soil and seismic excitation conditions. A finite element model was developed and validated against existing experimental data (Ali Al-Gharbi earthquake, PGA = 0.1 g), showing acceptable convergence with a PGA difference of approximately 13.4%. Subsequently, a parametric study was conducted using the Koyna earthquake record (PGA = 0.33 g) on large-scale, three-story adjacent steel buildings with one embedded story. The major quantified findings justify the following conclusions: (1) The peak ground acceleration (PGA) and roof displacement are maximized at a normalized distance of d/a = 4 (1.37 g and 151.5 mm, respectively), representing increases of 33% and 1.4% compared to d/a = 2, indicating a critical distance threshold for seismic design. (2) Asymmetric building orientation increases PGA by 14.6% but reduces frictional shear stress by 5.2%, revealing a trade-off that can be exploited in dense urban planning. (3) Replacing box columns with equivalent pipe columns increases PGA by 20.4%, roof displacement by 2.25%, and frictional shear stress by 3.0%, demonstrating the superior seismic performance of box sections. These findings provide directly actionable design guidance for minimum separation gaps, orientation strategies, and column section selection in earthquake-prone urban environments, thereby advancing both the scientific understanding and practical application of SSSI in seismic engineering.