Out-of-plane large displacement analysis of unreinforced masonry façades

The buckling behavior of slender unreinforced masonry (URM) walls subjected to axial compression and out-of-plane lateral loads is investigated through a simplified “homogenized” procedure. After a preliminary analysis performed on a unit cell meshed by means of elastic FEs and non linear interfaces, macroscopic moment-curvature diagrams so obtained are implemented at a structural level, discretizing masonry walls by means of rigid triangular elements and non linear interfaces. The non linear incremental response of the structure is accounted for a specific quadratic programming routine where second order effects are suitably accounted through geometrical stiffness matrix. The finite element model, applicable under various load and restraint conditions, incorporates material and geometric nonlinear analysis of slender URM walls and has the capability of capturing post-cracking and post-buckling behavior of the URM walls in an approximate but suitable way. As validation of the approach proposed, buckling behavior of some existing experimental pre-compressed four-point bending tests is reproduced.