Influence of Masonry Infills on Seismic Performance of an Existing RC Building Retrofitted by Means of FPS Devices

The safety assessment of existing structures in areas with a relevant seismic hazard is one of the major topics for engineers since many existing reinforced concrete structures have been realized disregarding seismic design with minimal details with respect to present practice. In this context, seismic assessment is a primary issue in order to identify the best retrofitting solution with the aim of enhancing the efficiency of existing buildings. In recent years, with the aim to enhance the seismic behavior of reinforced concrete (RC) structures (with particular care to existing ones), the system of seismic isolation adopting friction pendulum (FPS) devices proved to be among the most diffuse and effective solutions. The purpose of this paper is to explore the effectiveness of the refurbishment using FPS with single concavity devices on the performance of one irregular existing RC building placed in a highly seismic area of central Italy. First, the geometric and material characteristics of the building have been determined within the approach based on the "knowledge levels". Second, a suitable numerical model based on a fiber-modeling approach has been established using SAP2000, including relevant mechanical non-linearities. Then, a set of 21 natural seismic inputs, inclusive of 3 accelerations over vertical and horizontal directions, was adopted with the aim of performing non-linear (NL) dynamic simulations. The NL dynamic simulations have been performed considering the structural system, both inclusive and not inclusive of the FPS isolator devices. The influence of the actual distribution of infill masonry panels on the overall behavior of the structure has also been evaluated in both of the cases mentioned above. Finally, the outcomes deriving from the NL dynamic simulations were helpful in assessing the advantages of the intervention of retrofitting to improve the seismic performance of the building, highlighting the influence of masonry infills.