Seismic modelling and analysis of reinforced concrete structures with steel buckling-restrained braces

Most of the existing reinforced concrete buildings have been designed according to early seismic provisions or, sometimes, without applying any seismic provision. Some problems of strength and ductility, like insufficient shear strength or local mechanisms could characterize their structural behaviour. Therefore, the evaluation of the reinforced concrete (RC) building seismic capacity is an important topic in the engineering practice and also in the research field for both the assessment of the seismic vulnerability and the choice of appropriate retrofitting solutions to be applied. In particular, the seismic upgrading of RC framed structures can be carried out by means of the introduction of new structural elements capable of dissipating part or all of the energy transmitted by the earthquake. Among the possible seismic retrofitting strategies, the use of buckling-restrained braces (BRBs) has been analyzed in this work. In fact, the results and the experiences matured within the ILVA IDEM project (Mazzolani 2006) proved that BRBs can be one of the most effective systems for the improvement of the lateral capacity of RC frame structures. This work concerns the main modelling issues and the evaluation of the efficiency of steel bracing systems previously tested (Mazzolani, 2006). Namely, the effectiveness of the tested dissipative bracing in rehabilitating the analyzed buildings has been examined by means of non-linear analyses using various ground motion records.