МЕХАНИЗМ ОБРАЗОВАНИЯ ТРЕЩИН В КЛАДКЕ ЛИЦЕВОГО СЛОЯ НАРУЖНЫХ СТЕН ПРИ ТЕМПЕРАТУРНЫХ ВОЗДЕЙСТВИЯХ

Abstract

On the basis of the carried out experimental and numerical studies, the mechanism of crack formation in the masonry of the face layer with flexible ties under temperature influences has been established. Experimental studies were carried out for five years on a floor-high fragment of a building formed by external three-layer walls resting on a monolithic reinforced concrete slab. Numerical studies were carried out using the author's specialized program for calculating masonry structures, which implements the finite element method, taking into account structural nonlinearity. The program was verified by comparing the calculation results with the experimental data, as well as at the stage before the formation of cracks using the LIRA-SAPR program. It is shown that, depending on the ratio of the tensile strength of the masonry along the vertical joints and the cut along the horizontal mortar joints, different variants of crack development are possible. Vertical cracks, like expansion joints, reduce tensile and shear stresses. Cutting the masonry along the horizontal mortar joint at the base of the wall leads to a reduction in the length of the area of influence of the floor slab. Together, this leads to a decrease in the level of tensile and tangential stresses and damping of the crack propagation process. At the top of the wall, the effect of the floor slab on the stress-strain state of the masonry is relatively small and the temperature deformations there are close to free. This made it possible to apply a simplified methodology for assessing the crack opening width. A method is proposed for calculating the facing layer masonry for temperature effects and for assigning distances between vertical expansion joints.