Out-of-plane seismic assessment of URM infills accounting for in-plane/out-of-plane interaction in a non-linear static framework

In the Mediterranean area, Reinforced Concrete (RC) buildings are usually provided of Unreinforced Masonry (URM) infill wall panels. When subjected to the seismic action, these non-structural elements are sensitive to the displacements produced in the In-Plane (IP) direction and to the acceleration in the Out-Of-Plane (OOP) direction. The damage due to IP displacements reduce the OOP capacity and vice-versa: this phenomenon is called IP-OOP interaction. In this paper, an Eurocode-based out-of-plane safety assessment is carried out on the infills of case study new RC buildings for different infill layouts, in order to define PGAs activating the first OOP infill collapse. This “code-based” approach neglects the IP-OOP interaction and the primary RC structure non-linearity. The OOP seismic safety assessment is then carried out in a non-linear static framework (“reference approach”) accounting for IP-OOP interaction and structural non-linearity by applying appropriate literature acceleration floor spectra and relationships for the OOP strength degradation due to IP actions. The PGAs associated to the first OOP infill collapse estimated through the reference approach and through the code-based approach are then compared, showing their significant overestimation if a code-based approach is applied.