IMPROVEMENT OF THE DEFORMATION MODEL FOR THE CALCULATION OF BENDING ECCENTRICALLY STRETCHED REINFORCED CONCRETE BEAMS

Abstract

The study of the processes of formation and development of cracks in exploited reinforced concrete structures remains to this day one of the most urgent and at the same time the most complex issue in the theory of reinforced concrete. As practice shows, for the majority of exploited reinforced concrete structures, the onset of the limiting state is not due to the exhaustion of the bearing capacity, but to the formation and excessive crack opening at the operating load levels.In this article, the authors investigated the cracking of bent eccentrically stretched reinforced concrete beams. After processing of the experimental data with the help of an effective computer program COMPEX, mathematical models of longitudinal tensile forces were obtained, causing the appearance of normal cracks in stretched and later compressed bending fibers. The authors also analyzed the models obtained, which showed that the eccentricity of its application exerts a decisive influence on the magnitude of the longitudinal force that causes the appearance of normal cracks. Comparison of the calculated values of the longitudinal force with the help of the layered deformation model adapted by the authors, which causes the occurrence of normal cracks in this or that zone of the beam, with experimental data confirmed the need to take into account the initial technological damage of the concrete of the elements under study, since it significantly (by 10 ... 20%) reduces them real crack resistance.It is established that the eccentricity of the longitudinal force affects the strength of the prismatic sites of the prototypes indifferent ways.
Thus, the strength of inclined sections of eccentrically stretched beams with an increase in the relative eccentricity e / h _0 from -0.25 to +0.25, on average, decreases by 38%.