ASSESSMENT OF THE RESISTANCE OF CONCRETE TO FORCE DEFORMATION AND DESTRUCTION

Abstract

A critical analysis of the creation and development of the theory of calculation of reinforced concrete structures was carried out, and the need for its improvement based on the deformation-force calculation model, which is implemented using full experimental diagrams of the deformation (state) of concrete, was substantiated. In particular, the descending section of the σb–εb (stress–strain) diagram is considered in order to highlight some critical values of concrete deformability. One of them is the εbR value, which fixes the starting point of the descending branch. The end point of the descending part of the full diagram can be fixed by the parameter eb,max – the limit deformation, which corresponds to its largest value reached at the end of the concrete deformation diagram, and the residual strength of concrete Rb,min corresponding to this deformation. As numerous experiments show, the development of concrete deformations and the shape of the σb–εb diagram significantly depend on the change in the rate of deformation during tests. It was established that the nature of the descending branch, in particular its length, largely depends on the rate of deformation. For absolutely identical concretes, by changing the rate of deformation, it is possible to obtain different ultimate deformability at the end of the σb–εb diagram. If you test high-strength concretes with a low rate of deformation, you can record a much larger such deformation at the end of the descending branch than for concretes of lower strength tested at a higher rate. The regularity of the dependence of the deformations at the end of the complete diagram on the rate of force deformation is substantiated: if this rate approaches zero, the limit deformation of such a diagram at the corresponding level of stress reduction will tend to infinity. Directions for improving the considered model by introducing various transformed diagrams of the state of concrete, reinforced and reinforced structural elements are also proposed. Such diagrams are modeled through experimental dependences of concrete parameters σb–εb, taking into account the influence of various physical, technological, power and other factors.