Metallic and fluid viscous dampers for seismic protection of infilled frame buildings

Seismic retrofit of reinforced concrete (RC) frame buildings should target a proper protection not only of the structural skeleton, but also of the non-structural elements interacting with it under lateral loads, and particularly of masonry infills and partitions. Hence, the response of the latter should be properly simulated in assessment analyses carried out in current state, and the rehabilitation strategies be selected in order to provide adequate combined enhancements of structural and non-structural performance. This topic is developed in the study presented herein, where a representative case is examined, i.e. a 6-storey residential building with RC frame structure situated in L’Aquila, Italy, designed in compliance with the 1986 edition of the Italian Seismic Standards. In the assessment and retrofit design analyses, infills and partitions are modelled by means of diagonal no-tension struts with multilinear pivot type hysteretic behaviour. Based on the response evaluated in current conditions, two different retrofit solutions are proposed, both consisting in a dissipative bracing system. In the former solution, the system is equipped with Added Damping and Stiffness (ADAS) steel devices, whereas in the latter with Pressurized Fluid Viscous (PFV) dampers. The paper reports: the characteristics of the case study building; the computational models adopted in the analyses; the design of the two protective systems; a performance valuation in current and retrofitted conditions; checks on the correlation of the response of the ADAS and PFV-equipped dissipative bracing systems with the hypotheses formulated in their sizing processes; and a comparison between the protection capacities offered by the two technologies.