Зчеплення арматурних стержнів різних діаметрів класу А500С з бетоном

Abstract

Наведено результати експериментальних досліджень зчеплення бетону з арматурою серповидного профілю (класу А500С) діаметрів 10, 14, 16, 18, 22 мм та запропоновано формули (2) і (3), які можуть бути використані для розрахунку анкерування арматури.

Summary. In the production of the reinforced concrete structures comparatively new reinforcement crescent profile (ДСТУ 3760 – 2006), the adhesion of which with the concrete is not studied enough, has been used in Ukraine since the early third millennium. According to the research of Prof. J.A. Klimov the value of relative shear area of the transverse lug, that influences the adhesion with the concrete in the bars crescent profile, is in 2.4 – 3.7 times less than the corresponding values of screw profile rod that was used before. Therefore, it is necessary to use the correction factors for calculation of the class A500S anchoring reinforcement. The most important factor, which provides mutual work of the reinforcement and concrete in the reinforced structures is the adhesion at the contact between them. According to the researched results, the adhesion strength depends on the adhesion in concrete performances on the periodic profile reinforcement surface; friction forces that are developed under the reinforcement and concrete, contact caused by its shrinkage; reinforcement and concrete cementing, caused by the cementing property of the adhesive gel. The greatest influence on the adhesion strength is the first factor – it provides about 75% of the total sliding resistance of the reinforcement in concrete. If the reinforcement is smooth, the sliding resistance decreases in 2 – 3 times. The results of experimental studies of the concrete adhesion with crescent profile (class A500S) reinforcement of 10, 14, 16, 18 and 22 mm diameters are presented in the article. Samples were made in the form of concrete prisms of square cross section with 15 cm sides. The prisms height was determined by the standard length of anchoring rods, which was 5d (d – diameter rods). Reinforcement rods were arranged in the prisms so that their longitudinal axes coincide, and protruding parts of rods made possible to be fastened in the clutch press on one side, and on the other (free) – to measure its displacement (sliding) toward the prisms end using a tracer. In the experiments it was revealed that the value of tangential stresses of concrete and reinforcement adhesion depends on its diameter and can be be taken into account by introduction of an additional factor kd, which can be found by the formula (3). The greatest shear area is for the 16 mm diameter rod, so the tangential stresses in them are the greatest. It is testified experimentally.