Structural Weakness of OGS Buildings: A Seismic Fragility Study in Urban India.

Open ground story (OGS) buildings, prevalent in urban areas of countries like India, are structurally unique due to the absence of infill walls in the ground floor. This characteristic increases their seismic vulnerability. Traditional design practices often neglect the stiffness contribution of upper-story infill walls, leading to inadequate ground floor column design, which cannot withstand the amplified bending moments and shear forces during an earthquake. This study identifies the most vulnerable story in OGS buildings through a comprehensive seismic fragility analysis. The findings from the probabilistic seismic demand model (PSDM) log-log graph reveal that the ground floor is the most vulnerable, exhibiting significantly higher inter-story drift (ID), compared to upper levels, due to its reduced lateral stiffness from the absence of infill walls. ID, used as the demand variable in a power law model, captures this vulnerability, providing critical insights into the ground floor's heightened risk during seismic events. [ABSTRACT FROM AUTHOR]