Seismic assessment and selective retrofitting of an underdesigned RC frame

The seismic performance of a reinforced concrete (R/C) frame tested in the European Laboratory for Structural Assessment – ELSA of the Joint Research Centre – JRC (Ispra, Italy) has been recently assessed through nonlinear dynamic and static pushover analyses. The frame was designed only for gravity loads, since it was intended to be representative of the typical design and construction practice in many Southern European countries in the 1960’s. As reported in this paper, accurate numerical models were developed to reproduce the seismic response of the above-mentioned R/C frame in both the original and retrofitted configurations, and comparisons with experimental results were carried out. Seismic assessment procedures based on nonlinear dynamic analyses were applied to investigate the ductile and brittle mechanisms of the frame according to Eurocode 8 and to Italian Seismic Code (OPCM 3431). A simplified approach using nonlinear static pushover analyses was also adopted for the seismic verification of the global performance of the frame. The numerical predictions obtained by means of two seismic assessment procedures were compared and verified on the basis of the experimental results, and the effectiveness of selective retrofitting interventions aimed at increasing the capacity and ductility of the columns was evaluated as well. A detailed description of the seismic assessment procedures used to evaluate the seismic performance of the bare and retrofitted R/C frames is presented together with the most significant findings of the entire research project.