Seismic Performance of RCC Buildings on Hill Slopes: Determination of Threshold Ground Slope

The performance of reinforced cement concrete (RCC) hill buildings under seismic loading is less studied when related to the effects of varying ground slopes, especially to identify the critical threshold ground slope at which seismic demands and structural behavior change drastically. In the present study, building models on slopes ranging from 0° to 60° (in 7.5° increments) were analyzed, considering stepback-setback configurations. Key seismic parameters such as interstory drift, base shear, roof displacement, and overturning moment were evaluated to identify critical shifts in structural behavior through nonlinear time history analysis using representative ground motion records scaled to the maximum considered earthquake (MCE) level. Performance points were determined using demand-capacity curves obtained from pushover analysis to assess structural resilience. The findings revealed that up to 30° ground slopes, hill buildings under consideration exhibited predictable seismic responses with manageable drift, roof displacement, base shear, and overturning moment demands. However, beyond 30°, structural performance deteriorated due to increased stiffness irregularities, localized stress concentrations in short uphill columns, reduced energy dissipation, and heightened torsional effects. These shifts indicate a transition from ductile to brittle behavior, making buildings on steeper slopes increasingly susceptible to damage.