Steel bracing systems for the seismic upgrading of RC structures

Reinforced concrete constructions represent the largest part of the built heritage in the Euro-Mediterranean region because they characterize the related principal way of construction during the 20th Century. The widespread high seismic vulnerability of such constructions is mainly due to the fact that, primarily in the case of structures erected more than 20 years ago, they are usually designed to resist gravitational loads only. Hence, the possibility of resisting horizontal actions, e.g. seismic, is essentially due to overstrength effects. Considering the enormous diffusion of reinforced concrete constructions designed for vertical loads only, in recent years we have seen a growing interest in the establishment and development of innovative seismic protection systems able to improve the seismic behaviour of such constructions and also retain their original structural features. This paper describes the use of metallic bracing systems for the seismic retrofitting of reinforced concrete buildings designed for vertical loads only. Both the experimental and numerical results of the studies carried out on these systems within the scope of the ILVA-IDEM Italian research project and the PROHITEH EC-funded project are shown.