In this study, the seismic performance of an under construction building was evaluated. The building is part of the Sultan Qaboos University Hospital and is located in Muscat, Oman. It is a 6-story, flat-slab system combined with four shear walls and peripheral beams. The building is divided into four parts by expansion joints. In this study, a 3D numerical model of the structure was created in ETABS. Fifteen natural earthquake records were selected from the Pacific Earthquake Engineering Research Center (PEER) database. The selected records were matched to the response spectrum. Spectral acceleration based on the first-mode was chosen as the intensity measure, and the damage measure was considered as the maximum inter-story drift. Incremental Dynamic Analysis (IDA) was employed, and 9-11 time-history simulations were run for each record on varying scales until the collapse was recorded. Each simulation produced a single discrete Intensity vs Damage point. By employing interpolation of the points, single IDA curve for each record was created. The model was assessed for Immediate Occupancy and Global Instability limit states which were defined as the points where maximum inter-story exceeds 0.2% & 1%, respectively. The mean capacity curve of the building was determined using multiple IDA curves. Then fragility functions were derived. The results indicated that the structure is safe as per the provisions mentioned in Omani seismic code.