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.