Seismic design of existing buildings equipped with fluid-viscous dampers according to two different systems: inter-storey dissipative braces and dissipative links to a stiff tower

Most of the buildings designed in the past often need seismic retrofitting to ensure the safety standard imposed by the technical codes. Fluid-viscous dampers represent an option to protect buildings also against high intensity seismic actions. This thesis focuses on the seismic improvement of an existing building in which the dissipation of the earthquake energy is assigned to an additional system of fluid viscous dampers (viscous energy dissipation) and the plasticization of structural elements (hysteretic energy dissipation). Fluid-viscous dampers are sized according to the Direct Five Step Procedure (DFSP). The seismic response of the building in several configurations has been evaluated by means of Time-History analyses. The idea is to analyze the behavior of the naked structure and compare it to the behavior of the structure equipped with dampers to see, globally and locally, whether the target performances imposed through the DFSP have been achieved in terms of response reduction factors. Dampers were designed according to two types of configurations: •Placed as inter-storey braces, leading somehow to a Stiffness Proportional Damping system. •Connected as dissipative links to an external tower adjacent to the structure, leading somehow to a Mass Proportional Damping system. A third solution has been studied being composed by the same dampers used in the SPD system but placed according to the MPD system. All the benefits that such systems bring to the building were analyzed and quantified, and we can state that: •Globally, the results show that the initial performance objectives have been achieved. •Locally, when the focus is on selected structural elements, still some criticalities remain on which further attention needs to be paid and specific local interventions should be envisaged aimed at strengthening the critical parts of the structures. The best results are given by the MPDSPD-Dampers configuration, since the efficiency of the system.