Seismic Vulnerability of Reinforced Concrete Hillside Buildings in Northeast India

Abstract eng:
In northeast India, rapid urbanization and limited available land has led to the construction of multi-story, reinforced concrete frames with masonry infill walls on steep hillsides of weak soils. Recent earthquakes in neighboring regions suggest that these buildings may be highly vulnerable to earthquake damage. This paper analyzes the seismic performance of archetypical hillside, reinforced concrete buildings with stepped foundations in Aizawl, Mizoram using incremental dynamic analysis, quantifying collapse risk and identifying potential failure mechanisms. The results show that shear critical columns exacerbate structural vulnerabilities created by stepped hillside configurations. In an earthquake, structural failure likely will begin with axial failure of the half-length base columns at the top of the slope, followed by sequential failures in downslope columns. Collapse is predicted to occur from exceedance of column shear capacity in the stories on stepped foundations. Sensitivity studies of alternative structural and material configurations confirm that current practice of increasing column dimensions at downslope column lines improves lateral strength, relative to uniform column configurations. In addition, utilizing larger transverse reinforcing bars changes column failure mechanisms and increases collapse margin for the expected seismic hazard. The findings demonstrate that improved column shear capacity and abovecode detailing may mitigate the seismic vulnerability of Aizawl’s hillside reinforced concrete buildings.

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