Seismic performance assessment of a non-ductile RC building retrofitted by steel bracing or fiber-reinforced polymers

This study investigates a displacement-based procedure for the seismic assessment and retrofitting of a six-storey RC structure, designed for gravity loads without specific earthquake-resistant provisions. The procedure is based on a simplified approach using nonlinear static pushover analyses and allows to compare alternative retrofitting strategies countering different structural deficiencies. Accurate numerical models were developed in order to provide reliable predictions of the behaviour of the building identifying the main structural deficiencies. Two retrofitting solutions based on alternative strategies were proposed for the RC structure. The introduction of concentric steel bracings decreased the displacement demand on the structure, thus reducing damage in structural members. A more uniform distribution of storey drift was observed throughout the height of the building. The application of FRP wrapping increased the deformation capacity of the columns and significantly enhanced the global ductility of the structure, without modifying the displacement demand. The validity of the simplified procedure and the effectiveness of the retrofitting interventions were assessed by nonlinear dynamic analyses.