CYCLIC BEHAVIOR OF RC BUILDING WITH SOFT STOREY

Abstract

Many urban multistorey buildings in India today have open first storey as an unavoidable feature. This is. primarily being adopted to accommodate parking or reception lobbies in the first storeys. The upper storeys have brick infilled wall panels. Due to sudden change of lateral storey stiffness in the -first storey, the first storey transform in soft storey and the inter storey drift in the soft first storey is large. So the soft storey building suffer sever damage due to concentration of deformation in the first storey during earthquake. Earthquake exposes the weakness in the structures. The structures, which may appear to be strong enough, may crumble like houses of cards during earthquake. Due to ignorance of the seismic behavior of the buildings, many wrong practices remain continued, till an earthquake exposes them. An experimental study has been done, to know the cyclic behavior and failure modes in the building open at the ground storey. For experimental study a three storey RC frame building with soft storey at the ground has been considered. The frame structure has been analyzed and designs by STAAD Pro,2001 software without consideration of earthquake loads, and then reduced at a `Scale (1: 4 )l. The detailing in all structural parts of the tested model done according to IS 456:2000. The effect of masonry infill wall has not considered during the designing of model, which we have as a equivalent diagonal strut during lateral loading. The model has been constructed on strong floor and subjected to alternate cyclic loading in the form of sinusoidal loading. The model has been tested upto ultimate failure. The hysteretic response, energy dissipation capacity, damping, degradation of stiffness at each stages of cyclic load has been studied. The results obtained from these test have been discussed in detail in the dissertation. During application of cyclic loading the cracks observed in the top and bottom portion of column in the first storey due to formation of plastic hinges. Each hinge must dissipate large amount energy, due to this the strength of column degrades and the column will make unable to support gravity loads, P-delta also increase the instability. There were no cracks in the upper storey columns and beams. The displacement ductility has been obtained from results was 3.99, which is less than any other RC frame building not open at the ground storey. From this study it is conclude that the buildings with sift storey are highly vulnerable to damage during earthquake shaking.