TO THE MASONRY STRENGTH DETERMINATION UNDER COMPRESSION

Abstract

Experimental samples of various shapes and sizes, which are proposed to determine the compressive strength of masonry, are considered. The nature of its destruction and the value of the ultimate load are analyzed. The results of our own experimental studies of brick pillars are described. Materials of studies of masonry plates, prisms and piers under axial compression are presented. The given dimensions, their ratio and the shape of the samples that are recommended by various researchers for testing in order to establish the compressive strength of masonry as its main characteristic. It certifies that there are no uniform requirements for the test procedure. The following cases of destruction of masonry under compression have been identified: shear along an inclined plane; double-sided crushing-splitting (tearing-off cracks in the middle of the height of the element, the formation of seal wedges under the load areas, the indentation of wedges into the body of the element). The influence on the strength of adding 15% Ceresite to the cement-sand mortar was established. Strength problems are solved for the described cases of failure. As a theoretical basis, the variational method of the theory of plasticity, developed at the Department of Building Structures at the National University «Yuri Kondratyuk Poltava Polytechnic», was used. Plastic strain is considered to be localized in thin layers on the failure surface, which is characteristic of the ultimate state of concrete under the shear. Neighboring regions are assumed to be completely rigid. Kinematic failure schemes are presented for these cases. Formulas are provided for determining the value of the ultimate load at a minimum power of plastic strain on the shearsurface. The need for further research has been established in order to make a reasonable choice of the shape and dimensions of the basic prototype to determine the compressive strength of masonry.