Assessment of the out-of-plane resistance of masonry infill walls

Observation of damage after earthquakes has highlighted that out-of-plane failures of masonry infill walls may often occur even in the case of low or moderate earthquakes, causing both casualty risks for people and unfavourable situations affecting the overall structural response. In recent years, several experimental tests have been carried out trying to determine the relevance of different parameters that may affect the out-of-plane carrying capacity of infill walls, such as the slenderness ratio and the boundary conditions of the panel, the mechanical characteristics of the masonry, the stiffness of the surrounding frame elements and the presence of cracks arising from prior in-plane damage. Several analytical models have been developed too, and also included in code provisions; the application of these models to experimental data performed in this paper shows that the problem is still open and need further investigation. As a general observation, analytical models underestimate or overestimate the ultimate load carrying capacity according to the type of frame and infills under consideration, thus showing that the validity of each model is limited to specific configurations.