Design procedure for the seismic retrofit of existing RC buildings with viscous dampers: a case study

This paper describes a study for the seismic retrofit of an existing RC hospital building using fluid-viscous dampers. The structure, located in Italy, was built in the earlier 70s and it was designed without considering the seismic action. Due to a change in the seismic classification of the territory, the location is now classified as a seismic zone. The building is characterized by eight storeys and by an asymmetric “T” shaped plan. The seismic assessment of the structure was performed by developing a non-linear model and by applying pushover procedures. The analyses showed that the existing structure is not adequate to sustain the design seismic actions. The considered retrofit strategy is based on the insertion of non-linear fluid-viscous dampers at each storey. Two options were examined for the rehabilitation: introduction of supplemental dampers only and combination of dampers and new shear walls. The design of the damping system was performed according to a procedure based on energy criteria and considering the non-linear behaviour of the structure. Moreover, due to the irregular configuration of the building, the design of the damping system was extended considering the spatial model and different vibration modes