Concrete Bi-Modulus Analysis in the Estimation of Stress State of the Normal Sections of Reinforced Bending Element

Special aspects of evaluating the cracking resistance of beams with prestressed reinforcement in the program of their bench tests

“…It should be noted that expressions (11)-(14) are deduced based on the traditional view of the behavior of reinforced concrete, based on which concrete is traditionally considered a homogeneous isotropic material, working with a modulus of elasticity in tension equal to the modulus of elasticity in compression. At the same time, the paper [10] points out objective reasons for the difference in the elastic moduli of a concrete when working in compression and tension and the validity of considering concrete a bimodular material in the behavior of a bending element [11,12], the compressed zone of which works with modulus of elasticity in compression, and stretched zone with modulus of elasticity in tension. Earlier, expressions (9), (10) refl ected the differentiated approach to the evaluation of stresses of compressed and stretched zones, taking into account the elastic moduli characterizing the operation of these zones.…”

“…As an alternative, block of expressions (11)-(14) were suggested as solutions. But in this case, the fact is important that the geometric characteristics, in particular, the reduced moment of inertia I bred in expressions (11), (12) is different in comparison with the moment of inertia in expressions (13), (14) both in quantitative terms and semantic content. As the block of expressions (11), (12) and the block of expressions (13), (14) characterize the effect of bend-ing moments of different sign on the beam, when it is quite likely that the concrete is bimodular in the bending structure.…”

“…But in this case, the fact is important that the geometric characteristics, in particular, the reduced moment of inertia I bred in expressions (11), (12) is different in comparison with the moment of inertia in expressions (13), (14) both in quantitative terms and semantic content. As the block of expressions (11), (12) and the block of expressions (13), (14) characterize the effect of bend-ing moments of different sign on the beam, when it is quite likely that the concrete is bimodular in the bending structure. Indeed, if at the prestressing stage, the concrete of the lower zone of the beam compresses and works with the modulus of elasticity in compression, then at the next test stage, when the beam is loaded with a vertical test load, the zones of compressed and stretched concrete are changed.…”