A 8-DOF TRUSS ELEMENT FOR FRCM RETROFITTING OF MASONRY WALLS IN-PLANE LOADED

A 8-DOF non-linear truss finite element specifically conceived to study an FRCM reinforcement applied to in-plane loaded masonry walls is proposed. The reinforcing package is modelled considering separately the central elastic fibre grid and the two upper and lower inelastic matrix layers; matrix and fibre are considered in a monoaxial state of stress, mutually exchanging shear stresses at the interface. The truss element is therefore constituted by three constant stress trusses mutually connected by shear springs located at the nodes, representing the interfaces between contiguous layers. The constitutive relation assumed for the interface exhibits softening with residual strength. The internal matrix layer exchanges also tangential stresses between the reinforcement and the underneath masonry by means of an elastic interface. The accuracy of the finite element proposed is evaluated on various examples of masonry walls in-plane loaded.