Seismic Performance Assessment of Buildings Located on Hillside Slope

In the seismically active Indian Himalayan region, lack of available flat lands and ever-increasing housing needs have led to widespread construction of multi-storey reinforced concrete moment frame buildings on hilly slopes. Such buildings have foundation at different levels and columns of varying height to accommodate ground slope, introducing stiffness irregularity over the height of the structure. During an earthquake, this can lead to stress concentration in structure and may make them more vulnerable to collapse as compared to their regular counterparts. The primary objective of this study is to evaluate the seismic performance and factors influencing collapse capacity of buildings on hilly slopes designed as per modern Indian seismic building codes, which is not extensively investigated in past. To this end, two-dimensional numerical building models capable of simulating flexural and shear failure are created in OpenSEES for modern Indian seismic code compliant reinforced concrete special moment resisting frames located in city of Aizwal in the Himalayan region of India. The collapse capacity of the nonlinear building models is evaluated using incremental dynamic analysis for a suite of site specific ground motions. The seismic collapse fragility curves are developed as a metric to assess the seismic vulnerability of buildings. Buildings located on slope have lower median collapse capacity as compared to buildings located on flat grounds. The seismic response of buildings located on slope is particularly influenced by type of configuration and building height. The median collapse capacity [Sa(T=1s)] decreases by 20% to 42% with increase in slope angle from 5º to 30º as compared to building on no slope