Gauging seismic resilience of existing structures considering new Pakistan building code (BCP 2021)

Abstract

Pakistan had its first legally enforceable building code published in 2007 in the wake of 2005 earthquake. Harsh lessons learnt from that earthquake made the Government realize the need for a stringent building code, resulting in the creation of Building Code of Pakistan 2007 (BCP 2007). Fourteen years later, Pakistan Engineering Council redeveloped the engineering code, titled Building Code of Pakistan 2021 (BCP 2021), to make it is in line with the modern advancements in earthquake engineering knowledge. The new code comprises computational methodologies based on data that is more robust. Literature available has relatively lacking information regarding assessment of a structure as per new and old building codes. This study aims to address this research gap by gauging the relative performance of a high-rise structure, situated in a seismically vulnerable region in Pakistan, with respect to BCP 2007 and BCP 2021. In this regard a high-rise structure situated in Islamabad has been analyzed using Equivalent Lateral Force method and Response Spectrum Analysis method. Maximum story displacement and story drift have been studied using a computer program known as ETABS (based on SAP 2000). Results have shown that BCP 2021 is relatively more structurally demanding than BCP 2007. For instance, maximum spectral acceleration calculated as per BCP 2021 for a high rise structure, situated in Islamabad, is about 24% greater than maximum spectral acceleration calculated using BCP 2007 guidelines. Furthermore, certain load combinations as per BCP 2021 produced maximum story displacement and story drift by more than 4% compared to BCP 2007. Thus, the new building code regulation would require structural retrofitting of high-rise structures built as per old building code.