Improving the Seismic Resilience of Existing Braced-Frame Office Buildings

The concept of seismic resilience is defined as the capability of a system to maintain a level of functionality or performance in the aftermath of an earthquake event. In the research reported in this paper, a methodology for the seismic resilience assessment of existing braced-frame office buildings was developed. In this context, damage levels were defined as function of performance levels associated to earthquake intensity. Furthermore, fragility curves were derived from incremental dynamic analysis (IDA) curves obtained from time-history analyses using computer software and both aleatoric and epistemic uncertainties were considered. To illustrate the previously mentioned concept, a walkthrough of the methodology is presented in a case study comprising of existing 3-story and 6-story concentrically braced-frame (CBF) office buildings located in eastern Canada (Montreal and Quebec City) and western Canada (Vancouver). These buildings were designed in agreement with Canadian national code requirements. The proposed retrofit strategy is according to a United States standard and the retrofitted office buildings should meet the so-called basic safety rehabilitation objective class. In addition, all studied retrofitted buildings show enhanced earthquake resilience.