Integrated seismic and slope stability evaluation of reinforced concrete buildings constructed on sloping ground

Abstract

Rapid urbanization in seismic-prone hilly regions has led to an increasing demand for reinforced concrete (RC) buildings constructed on sloping ground, where structural irregularity and slope instability jointly govern safety. This study presents an integrated assessment of the seismic performance and slope stability of step-back (SB) and step-back–setback (SSB) RC buildings in hilly terrain. Eight structural configurations incorporating basements, shear walls, and bracing systems were analysed at slope angles of 20° and 25° in accordance with IS 1893 (Part 1): 2016. Structural response was evaluated using response spectrum analysis in ETABS, while slope stability was assessed using the Morgenstern–Price limit equilibrium method implemented in GeoStudio (SLOPE/W), enabling simultaneous consideration of structural demand and ground safety. Results indicate that maximum top displacements (approximately 35–47 mm) for all models remain within the code limit, although simple step-back buildings on 20° slopes approach borderline safety. Inter-storey drift ratios for all configurations remain below the permissible limit of 0.004, with shear wall systems exhibiting localized drift concentration in upper storeys due to stiffness irregularity. Base shear demand is strongly influenced by structural stiffness, increasing from about 2–3 kN in flexible step-back frames to 17–18 kN in step-back–setback buildings with combined shear wall–basement systems, thereby imposing higher foundation demands. Soil–structure interaction analysis reveals that setback configurations promote more uniform base reaction distribution compared to step-back buildings. Slope stability results demonstrate high sensitivity to slope angle in weak soils, with factors of safety reducing to near-critical values at 25°, while stronger residual soils maintain adequate stability. The study highlights critical trade-offs between seismic safety, soil response, and construction economy, providing practical guidance for the design of RC buildings in seismic hilly regions.