Behavior of RC Buildings Located on Hill Slopes under Earthquake Shaking

Abstract

Buildings on hill slopes have suffered significant damage from past earthquakes due to poor design and construction practices. Therefore, Indian building code restricts the natural period of building on slopes based on their shortest height. Different building configurations located on hill slopes perform differently in the event of an earthquake, making it necessary to check the applicability of provisions using elastic and inelastic analyses. This study investigated a spectrum of two-dimensional (2D) RC moment frame building configurations (with or without including infill walls as an equivalent strut), including (1) type of building configuration; (2) angle of slope; (3) boundary conditions; and (4) varying height of buildings using modal analysis, equivalent static analysis, and response spectrum analysis. Mass participation (from 80% to 37%) and base shear decrease due to extreme short columns, which demand massive forces; interstory drift decreases for buildings on hill slopes, but increases drastically by varying the boundary conditions. The responses from nonlinear static and dynamic time-history analyses were studied based on the capacity curve, performance point, and level of damage toto structural elements under the maximum considered earthquake (MCE). The presence of struts increases lateral stiffness and lateral strength for building on slopes, resulting in less damage to structural elements than regular buildings (BC1). However, damage to beams and columns is more common in bare-frame buildings than in buildings with struts, because the struts sustain more damage. Although a few building configurations on slopes incurred less damage (e.g., step-back setback buildings, due to decreased stiffness along the height), more damage is evident in the struts of other buildings on slopes. Thus, strut failure may cause a building to behave like a bare-frame building under MCE demand, sustaining more damage; this also was demonstrated with a three-dimensional (3D) building on slope. Thus, designing buildings based on code-based natural periods by assuming the sloped region to be rigid may not be valid for all building configurations. It is necessary to account for other critical parameters while placing restrictions on the building code provisions.