Seismic performance assesment of reinforced concrete framed buildings in Sri Lanka : a case study)

Abstract

Sri Lanka is considered to be in an aseismic zone (zone 0) away from major plate boundaries or any active faults. However, the first Earthquake hazard recorded on 14th April 1615 in Colombo with about 2000 deaths and destroying 200 houses. Since then, there have been many seismic events in Sri Lanka and neighbouring areas which are small to moderate in magnitude of which the tremors were felt by the people in some of the regions in Sri Lanka. Therefore, Sri Lanka has to be considered to be situated in higher seismic zones with respect to the seismic risk for the structures. Despite the above situation in Sri Lanka, almost all the buildings have not been designed and detailed for earthquake resistance. Hence, it is high time to commence not only the design and detailing of the buildings for seismic resistance but also the seismic assessment and retrofitting of the existing important buildings. Nevertheless, detailed seismic performance assessments considering the in-situ conditions of die buildings are new to Sri Lanka. Therefore, as an initiative for such future assessments, this study appraise the applicability and importance of pushover analysis for seismic assessment of a medium rise reinforced concrete framed building having a large floor area incorporating all As-built details. Pushover analysis procedure given in ATC 40 and FEMA 356 guidelines were used to carry out the performance assessment using SAP 2000. It is found from the study that the building performs at Immediate Occupancy performance level for serviceability earthquake in seismic zone 1 (CA=0.06, Cv=0.09). In addition, found that the building can safely withstand a maximum ground motion having acceleration coefficients of Ca=0.11 and Cv=0.17 performing at Immediate Occupancy performance level. Furthermore, it concludes that the pushover procedure is applicable and realistic results can be obtained for the building considered.