Earthquake Response of Reinforced Concrete Frame with Open Ground Storey

Abstract

Open ground storey buildings have consistently shown poor performance during past earthquakes across the world. For example during 1999 Turkey, 1999 Taiwan and 2003 Algeria earthquakes, a significant number of them have collapsed. For instance, the city of Ahmedabad alone has about 25,000 five-storey buildings and about 1,500 eleven-storey buildings; majority of them have open ground storey. There are huge numbers of such buildings in urban areas of moderate to severe seismic zones of the country. The collapse of more than a hundred reinforced concrete frame buildings with in Ahmedabad (~225km away from epi-centre) during the 2001 Bhuj earthquake has emphasised that such buildings with open ground storey are extremely vulnerable under earthquake shaking. The presence of walls in upper storeys makes them much stiffer than the open ground storey. Still Multi storey reinforced concrete buildings are continuing to be built in India which has open ground storeys. These buildings are not designed as per the earthquake resistant design. It is imperative to know the behaviour of soft storey building to the seismic load for designing various retrofit strategies. Hence it is important to study and understand the response of such buildings and make such buildings earthquake resistant based on the study to prevent their collapse and to save the loss of life and property. Based on the above an attempt is made in this paper to assess the seismic performance of the soft storey reinforced concrete building by shake table test. EVASTATING earthquakes strike at a regular interval in various parts of India. About 60% of India's land area is reported to be under the threat of moderate to severe seismic hazard. Reinforced concrete frame buildings are built in India which has open ground storeys. Owing to the high cost of land and small sizes of plots, parking is often accommodated in the ground floor area of the building. Frame bays in the ground floor are not infilled with masonry walls, as it is done in the upper stories. These buildings are normally not designed as per the earthquake resistant design proposed in the BIS codes.