Seismic performance analysis of RC buildings with V-columns on sloping ground using nonlinear time-history and soil–structure interaction

Rapid urbanization in hilly regions has led to the increasing adoption of irregular structural systems such as V-column buildings, where seismic response is influenced by sloping ground conditions and soil–structure interaction (SSI). However, the combined effects of these factors are not well understood. This study investigates the seismic performance of a 15-storey reinforced concrete V-column building using nonlinear time-history analysis, considering different slope inclinations and soft-storey configurations. SSI is incorporated through an equivalent linear spring approach, and an energy-based time-history method is employed to evaluate damping evolution and energy dissipation. The results indicate that slope-induced geometric asymmetry and soil flexibility significantly affect structural response by increasing displacement, inter-storey drift, and torsional behavior. The position of soft-storey irregularity plays a critical role, with configurations having more uniform stiffness distribution exhibiting improved deformation control and reduced torsional effects. SSI further modifies dynamic characteristics through period elongation and enhanced damping. The energy-based approach provides additional insight into the evolution of damping and internal energy transfer mechanisms under seismic loading. The findings highlight the importance of accounting for slope, SSI, and vertical irregularity in seismic design, contributing to improved performance-based design strategies for irregular high-rise buildings.