Multi-Directional Fixed Crack Model Extended to Masonry Structures

The mechanical nonlinearity of a masonry structure depends on debonding and slip of masonry joints and the fracture of blocks like bricks and concrete. The present study proposes a behavioral simulation to idealize masonry joints by allocating three orthogonal planes, which are governed by the existing multi-directional crack model, and to represent the damage of blocks by using another three crack planes. The shear stiffness of the joint changes due to the disintegration of the infilling mortar caused by the shear slip of the joint, as well as the confining pressure dependence of the shear strength. Shear response analysis of a masonry structure considering this disintegration was carried out, and the applicability of the analysis model was validated. The following three types of structures were selected for validation: 1) masonry structures in which both joints and masonry blocks are damaged, 2) structures in which masonry blocks are primarily damaged but deformation is not concentrated in the joints, and 3) structures in which mortar joints are exclusively damaged but the masonry blocks are exempt of damage. It was confirmed that the proposed analysis model can analyze the damage mode of masonry structures. It evaluates yield strength as well and deformability is estimated on the safe side of an engineering viewpoint.