Seismic response of randomly infilled reinforced concrete frames with soft ground storey

Abstract

ABSTRACT Multistoried masonry infilled concrete (RC) frame with open ground storey has been recognized as a serious stiffness irregularity that has led to typical soft storey collapse of many buildings in past seismic events. Present study represents extensive static and dynamic analyses to investigate the seismic behavior of masonry infilled soft storied RC buildings. Several soft storied 2D frames with variation in number of storeys, number of spans, percentage of infilled frame panels, height to horizontal extent ratio as well as randomness of infill positions have been analyzed and the behavior of frames is investigated. Effect of variation of these parameters on base shear, natural period of vibration, storey drift etc. are studied. Results show that the base shear is significantly increased in presence of structurally active infill panels as compared to static analysis while randomness in the distribution of infill shows no appreciable influence. The findings show that seismic forces obtained from static analysis leads to significantly under-designed ground storey columns in soft storey buildings and are vulnerable during earthquake. Magnification of base shear as a function of amount of infill number of storeys are presented which may act as a guideline for the engineers towards safer design of columns and other elements of buildings with open and soft ground storey in a rational manner.