Seismic retrofitting of buildings with damped braces by using a computer-aided design procedure

Damped braces (DBs) can be an easy and not expensive retrofitting solution of reinforced concrete (r.c.) framed buildings, in order to attain a designated seismic performance for a given intensity of the ground motion. Most of the current dis-placement-based design (DBD) procedures of DBs only consider the capacity curve of an initially undamaged structure. However, structures may be initially damaged by previous earthquakes, so the proportioning of DBs should include the effects of the cumulative damage induced by previous loading cycles. In this study, a displacement-damage-based design (DDBD) procedure of hysteretic damped braces (HYDBs) is implemented in an automated application named DAMPERS. It is divided into six electronic sheets, each one having blank boxes editable by the user and grey boxes showing the outcome of the automated evalu-ation. A six-storey r.c. framed building, representative of the Italian residential housing stock constructed during the 1990s, is retrofitted with HYDBs designed through the proposed DDBD procedure with the support of DAMPERS tool. In order to assess the relevance of damage due to previous earthquakes, the retrofit-ting solutions are also obtained with a simplified DBD procedure. Three structur-al configurations are considered for the original and retrofitted structures: i.e. bare frame, with nonstructural MIs; infilled frame, with a uniform in-elevation distri-bution of structural MIs; pilotis frame, with no MIs at the ground floor and struc-tural MIs at the other floors. To check the effectiveness of the HYDBs, nonlinear seismic analysis of the test structures is carried out using the computation plat-form OpenSees.