Keywords: structural modelling, composite materials and structures, buckling load, carbon fibre reinforced polymer, seismic retrofit, masonry.

This paper reports on the results obtained by a numerical analysis carried out on a multiple leaf stone masonry very often used in ancient masonry walls, characterized by two or more rigid external leaves made from calcareous rock or blocks and mortar joints, with a very poor inner core leaf in mortar and stone aggregate. Firstly the numerical model was calibrated in order to determine the maximum load that the multiple leaf masonry can bear in the presence of eccentric loads by taking into account both the buckling phenomena and the mechanical behaviour of the no-tension strength of the material. The results, highlight a behavior significantly influenced by the elastic modulus of the materials, particularly that of the inner core. The numerical approach was carried out by considering the inner core either as a cohesion free material or a linear elastic material. Then, the enhancement of the global behaviour of the multi-leaf stone masonry reinforced by a technology based on the use of carbon fibre reinforced polymer (C-FRP) bars was evaluated with respect to both the unreinforced model and the traditional technique consisting of inserting some transverse masonry bricks that work as a tie. In the presence of reinforcement, the original scheme of a beam supported at the ends, which has been assumed for the wall is modified. The transverse ties connect the two external leaves forming a symmetrical system of two vertical elements connected by horizontal rods. The benefits in the limit of the buckling load determine an increase in the load-bearing capacity even in the presence of a higher elastic modulus of the inner leaf. The proposed reinforcement technology consists in inserting some transversal C-FRP bars through the thickness of the wall. The C-FRP ribbon obtained was glued on the masonry surface using a C-FRP strip glued around the C-FRP ribbons. From the results obtained it can be seen that the C-FRP reinforcement shows an excellent resistance, while those in stone (tuff) have a low tensile strength. The proposed technique provides an enhancement of global resistance of more than three times greater that of the original model .

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