16-DOF Finite Element for FRCM Reinforced Masonry Arches Subjected to Debonding: Preliminary Results at Structural Level

A 16-dof 1D finite element suited to study masonry arches reinforced with FRCM is presented. The nonlinearities are concentrated in matrix layers of the reinforcement, at the interface between substrate/reinforcement and matrix/fiber, and in mortar joints. Bricks are modeled with elastic elements, whereas the reinforcement is constituted by three trusses in parallel representing external matrix, central fiber, and internal matrix layers, mutually exchanging tangential stresses by means of shear springs applied at the extremes of the element, and finally the joints are interface elements working both under mode 1 and 2. A linear softening with residual tangential strength is assumed as constitutive law for the interfaces between substrate/reinforcement and matrix/fiber. Matrix is assumed elastic with linear softening in tension and infinite resistant in compression. The internal matrix layer is connected to the support by means of two elastic springs applied at the element nodes. The procedure is benchmarked on masonry pillars reinforced with FRCM and tested in lab, for which experimental data and a variety of previously presented results obtained through numerical models characterized by different levels of complexity are available, and on an arch made by bricks tested in situ. From the thorough analysis carried out on the global force displacement curves so obtained and an exhaustive study of non-linearities that develop in matrix layers, at the interface between substrate/reinforcement and matrix/fiber, and in mortar joints, the robustness and consistency of the method proposed are evaluated.