Crack resistance of centrally stretched combined re-enforced reinforced concrete elements

Abstract

Reinforced concrete structures, in which during normal operation the sudden appearance of cracks is not allowed occur in the practice of erection of buildings and structures in many cases

Such constructions, as a rule, are executed with prestressing of working rod armature that leads to additional power expenses. In the practice of construction, combined reinforced concrete structures are beginning to be used, in which rod work reinforcement and volume dispersed reinforcement with steel fiber are used at the same time. In such structures, the resistance to tensile forces from external loads increases significantly, but the use of such structures is limited due to the lack of methods for their calculation and determination of rational parameters of disperse reinforcement.

The article presents a method for determining the parameters of volume dispersion reinforcement with steel fiber of a centrally stretched reinforced concrete element on the example of calculating the wall of a cylindrical tank, in which during normal operation the formation of cracks is not allowed.

The method is grounded on a mathematically planned experiment, based on which a mathematical model was obtained to determine the strength of reinforced concrete and crack force in the wall depending on the main factors of influence: concrete strength, length of steel fiber and volume dispersion reinforcement. For a cylindrical tank for liquid with a diameter of 18 m and a height of 4.8 m based on the analysis of the obtained mathematical model of wall resistance to cracking and taking into account the expense of fiber per 1 cubic meter of concrete, the rational parameters of its volumetric disperse reinforcement are: when using concrete class C30 / 35 fiber length 60 mm with a expense of 50 kg per cubic meter of concrete; when using concrete class C32 / 40 fiber length 50 mm with a expense of 39 kg per cubic meter of concrete.

The final choice of the parameters of dispersed reinforcement from the above two must be determined by cost, based on the actual conditions of construction of the tank