Out-of-plane capacity equations for masonry infill walls accounting for openings and boundary conditions

A large part of 20th and 21st centuries' residential buildings is characterised by reinforced concrete, or less frequently steel, frames filled with masonry walls. Recent seismic events have shown that failure of infills may occur under moderate earthquakes, inducing a risk to life and limb of occupants, as well as to construction cost of the building. For this reason, researches have been devoted to the capacity of infill walls carrying out both analytical and experimental tests, also in the out-of-plane direction. These studies have identified the main parameters affecting the out-of-plane response of infill, such as the boundary conditions and the slenderness of the infill. In this study, a large data set of experimental tests is collected with the aim of investigating the influence of the main factors relevant for the infill response and to assess the suitability of different formulations proposed in the literature. It is found that, for the most part, such formulations underestimate the out-of-plane strength. Afterwards, numerical analyses are performed to investigate those situations that were scarcely considered in experimental campaigns, namely the presence of an opening (window or door) and of a gap between the infill and the top beam. Finally, taking into account all the considered parameters, a formula to predict the out-of-plane strength capacity of an infill is proposed.