MECHANISM OF NORMAL CRACKS LEVEL FORMATION AND OPENING IN BENDING REINFORCED CONCRETE ELEMENTS

Abstract

This article is devoted to experimental and theoretical studies of the main regularities and features of the normal cracks sequential formation and opening process in bending reinforced concrete elements. Experiments have confirmed that the real process of normal cracks formation in bending elements is multilevel. The most important characteristics of the test beams are given. According to their tests results, it was established that when calculating the normal cracks opening width in bending reinforced concrete elements, it is possible to limit the first two levels of their formation. For each of all the detected crack formation levels, the corresponding values ​​of not only the loads, but also the internal forces, the step and the normal cracks opening width have been established. A general and simplified method of calculating multi-level formation and opening of normal cracks in bending reinforced concrete elements is proposed. According to the research results, the feasibility of calculating the normal cracks opening width by successive accumulation of mutually displaced concrete and reinforcement is substantiated. The priority role of the non-linear function of the average stress adhesion of reinforcement with concrete in practical calculations of the bending elements crack resistance is confirmed. The developed calculation methods of normal cracks multi-level formation and opening in bending elements are also evaluated due to their comparison with existing methods. The effectiveness of those calculation methods in which the rate of normal cracks formation is directly related to the forces (stress) of the reinforcement to the concrete adhesion is statistically confirmed.