The Analysis of Stress Deformation State Peculiarities of Masonry Units and Bed Joints

In this paper, the analysis of various effects that have influence to the mechanical properties of masonry is made. Masonry is nonhomogeneous and anisotropic material composed of two materials with different stiffness properties. In order to analyze masonry deformations it is necessary to evaluate all effects that have influence to masonry mechanical properties (Table 1). The analysis of stress-strain state of masonry is presented in this paper. During the analysis of stressstrain state, the mechanical properties of masonry units and mortar were defined from experimental investigation of samples of unit and mortar materials. The following conclusions were reached based on the analysis of experimental data: 1) The deformations and stresses along the height of masonry unit distributes unevenly. The stresses and deformations near the bed joint are higher than in the middle of the unit (4 pav). 2) From experimental data it was determined that the deformation of bed joints mostly depend on contact zone between units and mortar. The contact zone deformation contains about 80…90% of all bed joint deformation. 3) The elastic modulus of mortar inside the composite is different from modulus of mortar specimens cast separately due to different laying and curing conditions. The elastic modulus values performed from composite were 15…25 times less than the values from standard mortar prisms (EN 1015-11). It is advisable to use real (defined from experiments) masonry units and mortar properties when detailed, numerical stress-strain analysis is performed. 4) Experimental analysis showed that bed joints have big influence to vertical deformation of masonry in axial compression. Masonry units have influence to mechanical properties of mortar joints. The experiment was carried out, during which dry and wet masonry units were used. Units were wet out to eliminate there absorption characteristics. Extra wet out units had an effect to the stiffness of bed joints (12 pav).