Seismic Vulnerability Assessment of Reinforced Concrete Buildings with Vertical Setback Irregularities

Abstract

Many devastating Earthquakes have occurred in the recent past, which have caused a huge loss to life and infrastructure. The main reasons for high vulnerability especially in developing countries like Pakistan are low strength materials, poor design and poor detailing practices. Irregularities in elevation or plan of the building structures increase the risk of failure. Past experience indicates that the irregular buildings are more vulnerable than the regular buildings. This study aims to check the seismic adequacy of vertical setback RC building stock by using the vulnerability assessment frame work developed by Kyriakides (2007), after incorporating Building Code of Pakistan (BCP, 2007). Three, four and six storey buildings with different setback configurations are considered. Irregularities of the buildings are quantified by selecting irregularity indices available in literature. The buildings are modeled in DRAIN-3DX and their capacity curves are developed using nonlinear static method. Damage is quantified using a damage index based on normalization of secant period against collapse period. The derived vulnerability curves of setback buildings show that these experienced more damage than the corresponding regular buildings. It is found that the damage increases with an increase in irregularity. This study is very useful for researchers and practicing engineers dealing with building structures located in seismic zones of Pakistan.