A study to evaluate the performance of the existing building by the development of fragility curves was introduced in this paper. A typical five-story residential government RC building becomes the target building, designed based on BS 8110 without incorporating any seismic action. It consists of plan and elevation irregularities. The target building was analyzed by performing Incremental Dynamic Analysis (IDA) and excited by several ground motion records through equally scaling from 0.1 g to 0.8 g with every 0.1 g increment. Nonlinear time-history analysis was executed using STERA 3D software and recorded the structural response in terms of maximum inter-story drift ratio (IDRmax). This study initiated two different methods of developing fragility curves: (1) using a limit state of five levels of performance-based seismic designs, and (2) the conditional probability of IDRmax exceeded the specified limit state of IDR with the aid of static pushover analysis. Both X- and Y-directions were examined to investigate the irregularity effect of the target building. Findings indicated that X-direction is weaker than Y-direction for both methods to reach or exceed specific performance levels and for the conditional probabilities of exceeding the targeted limit state at a given peak ground acceleration (PGA).
Keywords: Fragility curve, performance levels, limit state, incremental dynamic analysis