Coupling strength of class a500с rod reinforcement with steel fiber concrete of beam type specimens

Abstract

The coupling of reinforcement with concrete ensures their joint work from the beginning of loading of the structural element until its destruction. It depends on a number of factors that affect the reliability of anchoring rods in reinforced concrete, which must be taken into account when designing structures.

Fiber reinforcement can be considered as a type of indirect reinforcement that affects the bond strength with concrete. In this study, fiber reinforcement with bent ends of the HE1050 type, 50 mm long and 1 mm in diameter, was used.

It is known to use the three-factor design of the Box-Behnken experiment to obtain the regression equation, the function of which is the shear bond strength of the unloaded end of the rod 0.1 mm fb, and the arguments are the parameters affecting these stresses. This experimental plan was also used to study issues of crack resistance of composite reinforced steel fiber concrete stretched elements. In previous studies, we used a full four-factor experiment, and accepted the hypothesis of a linear influence of factors on the coupling stress fb. According to the results of experiments on pulling out rods of class A500C Ø 8 and Ø 12 mm from fiber concrete prisms 150 x 150 x 200 mm, the regression equation was obtained.

In this work, the beam method of tests for pulling out rods from fiber concrete is used. Evaluation of the experimental values ​​of  proved that the theoretical values ​​of , are greater than the experimental ones. The ratio of experimental values ​​to theoretical values ​​is within 0,79 – 0,88. Therefore, it is proposed to accept the right-hand side of the regression equation obtained from the results of experiments on pulling rods from prisms with the average value of this ratio of 0.84. This makes it possible to approximate experimental and theoretical data, and the mentioned ratio will be in the range of 0.95 - 1.05, which can be considered quite satisfactory.

In addition, in order to evaluate the effect of fiber reinforcement on the bond stress , two twin samples were made, which did not contain fibers. Stress  of fiber concrete samples exceeded the corresponding stress of concrete by 14-40% depending on  and  .