SEISMIC VULNERABILITY ASSESSMENT OF NON- SEISMICALLY DETAILED LOW-RISE INFILLED RC FRAME BUILDINGS IN PAKISTAN

Abstract

Abstract Pakistan is an earthquake-prone and seismically active region of the world. Typical RC frame buildings in Pakistan have poor confinement of beams and columns as their design is based primarily on gravity loads and equivalent lateral force procedure. These non-seismically detailed buildings are more vulnerable to seismic damage as compared to seismically detailed buildings. This study presents the seismic vulnerability assessment of low-rise non-seismically detailed infilled RC frame buildings in Pakistan. These buildings are then seismically detailed by providing confinement to beams and columns’ cross-sections following guidelines of NEHRP. Three existing low-rise case study buildings are selected, representing typical RC frame buildings in Pakistan. Two non-linear models for each case study building are created in ETABS, one model is based on poor confinement of beams and columns’ cross-sections representing existing buildings of Pakistan, and another model of the same case study building with seismic detailing of beams and columns’ cross-sections representing the improved buildings. Models are validated for brick masonry walls with an experimental investigation. Incremental dynamic analysis is performed to estimate the parameters required to develop the fragility curves. It can be observed that the seismic detailing has no effect on the achievement of slight damage (DS1) while at the design PGA level, seismic detailing (confinement of RC frame sections) reduces the probability of exceeding moderate (DS2) and extensive damage (DS3) from 86% to 50% and 41% to 3%. At MCE level PGA, probability of exceeding collapse (DS4) is reduced from 32% to 2% after seismic detailing of RC frame sections.