Experimental reemergence of the beams in two spilt, non-surface concrete beams for their low-cycle repetitive and familiar dressing

Abstract

In the article the results of tests of two-pass non-separable reinforced concrete beams under the influence of low cycle repetitive and sign-loaded loads, in which features of the change of the stress-strain state, changes of reference and spin bending moments and deformations of concrete and reinforcement in the process of loads are revealed in comparison with one-time static load. According to the results of experimental research of indecomposable reinforced concrete beams, the mechanism of deformation, the nature of the formation of cracks, their further development, as well as the redistribution of forces in the sections of beams from the beginning of loading to destruction, are also established. In the course of low-cycle repetitive loads, the process of changing these values stabilizes by 5-6 cycles. With regard to the deformation of indistinguishable beams for the effect of low-cycle shift loads and changes above the specified parameters, then there is a completely different picture. Analyzing the stress-strain state of beams at such loads, it should be noted that there is no clear stabilization above the above parameters. All this can be explained by changing the stiffness of the sections from the cycle to the cycle of alternating loads, as much as the cracks cross-section beams cut almost completely, dividing the beam into separate blocks. And from the cycle to the cycle, the number of cracks and their width of opening are increased, thereby reducing stiffness and increasing the curvature. All of the above has a significant effect on the nature of the redistribution of effort, that is, the reference and span moments. But when the limiting strains in the reinforcement on the support in the span are reached, the bending moments before the destruction are almost identical. Only, it should be noted that their values vary, depending on the nature and modes of loading, that is, the load bearing capacity is different, how much force at which the beams were destroyed different, as shown in Tables 2 and 3, where the forces at which the beams were destroyed by the actions of low cycle repeated loads F_u = 11,1 kN, and for the effects of low-cycle interchangeable loads F_u = 7.81 kN. At the same time, the beams loaded with a one-time static load collapsed at a force of F_u = 12.8 kN.