Comparative study of the code-prescribed design interventions for open ground storey buildings in India

Reinforced Concrete (RC) frame buildings with Open Ground Storey (OGS) have undergone severe to heavy damage, mainly in open storey columns resulting collapse of the entire building. Several national standards have recommended the design of open storey members with higher forces using some multiplication factors or stiffening elements like bracings to compensate open storey stiffness and strength irregularity. Aim of the manuscript is to assess the efficacy and ease of practice of several available design interventions prescribed by various national design standards to remove strength/stiffness irregularity in OGS buildings. An exhaustive comparative study has been carried out on the effect of design provisions recommended by various national seismic design standards on sets of mid-rise and high-rise infilled RC frame buildings with open ground storey designed as per relevant Indian standards, in deterministic, as well as probabilistic terms. The effect of relevant OGS design provisions on the seismic performance and consequent seismic fragility has been evaluated using pushover analysis in conjunction with HAZUS methodology. Design of OGS through higher forces using a multiplication factor ranging from 2.5 to 3 is found effective and more feasible solution in terms of seismic performance as well as ease of OGS building design for all practical purposes.