Seismic Performance Evaluation of Open Ground Storey Framed Building : A Simplified Design Solution

Open Ground Storey (OGS) framed buildings where the ground storey is kept open without infill walls, mainly for parking, is increasing commonly in urban areas. Vulnerability of this type of buildings was exposed in the past earthquakes. OGS buildings are conventionally designed considering a bare frame analysis ignoring the stiffness of the infill walls present in the upper storeys. This analysis ignoring the stiffness of infill walls underestimates the inter-storey drift (ISD) and thereby the force demand in the ground storey columns. Therefore a multiplication factor (MF) is introduced by various international codes to calculate the accurate design forces (bending moments and shear forces) in the ground storey columns. There is a wide range of disparity in the values of MFs and its scheme of application for design of open ground storey buildings proposed by various International codes. Present study is an attempt to study the performance of typical OGS frames designed with different scheme of MF and to arrive a simplified design solution based on reliability theories.