Interface modeling in load transfer mechanisms of multi-leaf masonry panels

Masonry heterogeneity and manufacturing imperfections affect structural behaviour of constructions; these unpredictable aspects are amplified in multi-leaf masonry walls by interfaces which play a main role on load transfer mechanisms and on global behaviour. In this paper, the performances of multi-leaf masonry walls subjected to compressive loads are investigated using experimental and numerical approaches. 9 experimental tests were performed on three-leaf specimens constituted by external leaves made of a regular pattern of brick elements and mortar joints, and a disaggregate internal core made of brick potsherds and mortar. FE models were developed to assess the interface interaction among layers through model updating procedure based on dynamic parameters experimentally identified at incremental load conditions, keeping fixed the mechanical parameters of external layers. FE models were updated by 13 parameters: i) unidirectional stiffnesses of 12 springs located between external layers and core; ii) elastic modulus of core. Updated models were tested through non-linear static analysis and results were compared with structural performances of multi-leaf masonry panels. Interface effectiveness regulated by different stiffness hierarchies among layers and between bricks and mortar joints handles the load transfer mechanisms and failure scenario. Compressive load is transferred through out-of-plane mechanisms triggered by maximum tensile stresses by 20% of failure load. In the plane the load is transferred with maximum compressive stresses at the ends (30% of failure load) decreasing centrally. Tangential stresses among layers are maximum near to load application and are linearly distributed in the plane of panels.