Influence of damage and boundary conditions on the modal properties of unreinforced masonry infill walls in reinforced concrete frames

Unreinforced masonry (URM) infill walls in reinforced concrete (RC) buildings are prone to seismic damage due to combined in-plane (IP) and out-of-plane (OOP) loadings. In particular, damage due to IP displacement demands promotes OOP collapse of URM infills (IP-OOP interaction). Thus, an experimental campaign based on static, cyclic and dynamic tests has been initiated to assess the influence of IP damage on the OOP response of masonry infills in RC frames. The present paper investigates the OOP dynamic response of 2D frames with URM infills in healthy state, when no cracking is present in the masonry panel as a result of IP static or cyclic tests, and after damage. The influence of damage on modal properties is assessed through the analysis of the variations of the experimental modal properties as well as by comparing the experimental results with those provided by a finite element model of the frames. Starting from the results of experimental tests and numerical models, sensitivity analyses are also carried out to assess the relative influence of material properties and boundary RC elements on the OOP dynamic response of the panel.