THE IMPACT OF THE DISPERSIVE REINFORCEMENT OF THE STREIGHT AREA IN REINFORCED CONCRETE BEAMS ON THEIR CRACK RESISTANCE

Abstract

The requirements for operational qualities of reinforced concrete structures – strength, resistance to cracks, stiffness, and survival probability are constantly increased. The way to upraise the reinforced beams resistance to cracks is to use dispersive reinforcing of under layer of concrete. In this case, operational qualities of reinforced concrete structures will mainly be affected by the percent of volumetric reinforcement with fiber, the thickness of the dispersive reinforced concrete layer, the percent of reinforcing with longitudinal armature and its mechanical behavior.

Although, until the present, the impact of dispersion-reinforced layer on operational factors of beams neither theoretically nor experimentally wasn’t explored.

In this article was developed a calculated model of the cross-cut of the reinforced concrete beam with dispersive reinforced concrete layer in lengthy area, based on stress-strain technique of calculation of the reinforced concrete constructions were received formulas for the definition of the tensely deformed condition of the cross-section and the moment of cracking.

For description of the mechanical condition diagram of the common and dispersive reinforced concrete was accepted function "stress-deformation" as fifth degree polynomial.

There was performed numerical mathematically designed experiment based on matrix of Box-Behnken plan. The percent of volumetric reinforcing, the percent of longitudinal reinforcing and the thickness of the dispersive reinforced concrete layer in beam lengthy area were accepted as an impact factors, and moment of cracking in beams – as an initial parameter. As a result of the performed calculations we have received full quadratic regression equation (mathematical model) for definition of the cracking moment in beam depending on investigated impact factors. The relevancy of regression coefficients were set by Student’s criterion, and the equation, by itself, describes the results of the investigation adequately. The mathematical model we have received, gives as the permission to take gauge in amount of the investigated factors impact on beams’ cracks resistance and to choose their optimum values. It was proved that, the existence of dispersive reinforced concrete layer in beam lengthy area can magnify their crack resistance two times and more.