Probabilistic assessment of an irregular existing RC structure: The effectiveness of the retrofitting intervention using FPS

The seismic assessment of existing structures is an issue of high relevance for researches and practitioners. In general, design codes of the past (e.g., during the ’60-’70) have not been conceived for seismic design and they report just limited recommendations for detailing of main members as columns and beams. With the aim to fulfil performance requirements of existing RC structures against seismic action (both concerning serviceability and ultimate limit states) several intervention approaches are available (e.g., active and/or passive control techniques). Over the last years, one of the most diffused technique is the use of passive seismic protection by means friction pendulum system (FPS). The purpose of this investigation is to investigate, with a probabilistic approach, the efficiency of the retrofitting intervention using single concave friction pendulum system (SC-FPS) on an existing RC structure placed in an area subjected to high seismicity. The herein considered existing RC building presents irregular configuration both in plan and in elevation and has been built without appropriate seismic detailing. Several non-linear dynamic analyses have been performed using fibermodelling approach and adopting multiple seismic records characterized by accelerometric components in three directions. The seismic performance has been evaluated for the structure with and without the retrofitting intervention by SC-FPS highlighting its effectiveness also in the case of irregular buildings.