MODELING BASICS OF MULTILEVEL NORMAL CRACKS FORMATION IN REINFORCED CONCRETE ELEMENTS AND STRUCTURES

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The model of consistent multilevel normal cracks formation is an integral part of the generalized deformation and force model of reinforced concrete elements and structures resistance by force influences. It is based on the most important patterns of reinforcement adhesion with concrete. It is based on the fundamental relationships of the mechanics of a deformed solid, which are expressed by the generally recognized system of static, geometric, and physical relations. To reveal the internal static uncertainty of the reinforced concrete elements cross-section, this system is supplemented by the analytical dependence of the state diagram of the reinforced concrete element and the function of compressed concrete boundary deformation.The first normal cracks occurrence of the first level in the reinforced concrete element is determined by the boundary deformations of the stretched concrete, which are fixed by the extreme criterion of its strength.The distances between the cracks are determined by the equilibrium of the maximum forces in the stretched concrete and the active adhesion forces in the area between the cracks. The force of reinforcement active coupling with concrete is proposed to be calculated by the nonlinear function of the average stresses of this coupling, justified by the power of expression. It is shown that for a centrally stretched reinforced concrete element, the distance between the first level cracks is inversely proportional to its reinforcement coefficient. The magnitude of the normal stresses in the tensile reinforcement at which cracks of the second level will begin to form is established.It is substantiated why for bending reinforced concrete elements the distances between normal cracks of new and previous levels will always differ from each other. In the developed model, the width of the most dangerous normal crack opening is calculated from the positions of successive accumulation of reinforcement and concrete mutual displacements.The developed technique is the basis of the engineering method of calculating the formation and discrete cracks opening at the operational stages of reinforced concrete elements deformation.