THE DETERMINATION OF PARAMETERS OF COMBINED REINFORCEMENT OF STRETCHED AND BENDING REINFORCED CONCRETE ELEMENTS WITH THE SPECIFIC CRACK RESISTANCE

Abstract

Recently, there has been an increase in the use of reinforced concrete structures withcombined reinforcement in construction, which makes it possible to increase the resistance of suchstructures to deformation and cracking. Dispersed reinforced concrete was used to cover roads, flooring in industrial buildings, the manufacture of curbs and more. For the construction of publicand industrial buildings, the use of combined reinforced structures has not been widely used, as noperfect method of their calculation has been developed.Combined reinforcement structures include concrete structures that are reinforced with steelrods and steel fiber, which is randomly arranged in the mass of concrete. The strength of reinforcedconcrete depends on such factors as: the strength of concrete, reinforcement with rod reinforcement,the type of fiber and its characteristics, the volume of fiber per unit volume of concrete, the size ofthe cross section of the elements. These factors affect the tensile strength of reinforced concrete bothdirectly and by their interaction. Therefore, determining the effective parameters of dispersedconcrete reinforcement is a complex multivariate task, its solution is proposed to be achieved byperforming mathematically planned experiments.When choosing the parameters of dispersed reinforcement of centrally stretched and bendingreinforced concrete elements (lower truss belt, arch tightening, cylindrical tank wall, beams, slabs),it is advisable to choose the strength of concrete fck, fiber length lf and volume dispersion coefficient.The optimal choice of values of these parameters is proposed to be performed using quadraticregression equations, which are based on the results of three-factor three-level mathematicallyplanned experiments, which are based on the matrix of the Box-Behnken plan.The obtained mathematical models make it possible to analyze the influence of dispersereinforcement parameters on crack formation forces in combined reinforced concrete elements andto determine their optimal values. The use of combined reinforcement allows increasing the crackresistance of reinforced concrete elements in two or more times.