Análise dos mecanismos de transferência de esforços de cisalhamento em peças de concreto armado convencional e reforçadas com fibras de aço e PVA

Abstract

Despite being the most used material in construction, there are still difficulties in estimating the shear strength of reinforced concrete, especially when fibers are used. The present study analyze the ultimate shear strength and cohesion, aggregate interlock, friction and dowel action mechanisms in the transfer of these forces. Four concrete mix ratios were used: CC1 a conventional concrete with gravel 1, CC0 a conventional concrete with gravel 0, CRFA a concrete reinforced with 0.5% steel fibers and CRF-PVA a concrete reinforced with 0.5% PVA fibers. Twenty-four cylindrical specimens were molded to determine compressive, traction and elastic modulus strengths and 12 push-off specimens for direct shear tests, three for each trait, with is a variant the presence of longitudinal reinforcement, its adherence condition and the characteristic maximum diameter of the coarse aggregate used. The results showed that the addition of steel fibers provided a significant increase in the compressive strength, traction and shear strength of the concrete, while the PVA fibers increased the compressive strength, but did not increase the shear or traction strength. Analyzing the proportional variation from one specimen to another of the same mix ratio, it can be seen that the presence of fibers negatively interferes with the adherence of the steel bar with the concrete. The results of conventional concretes were compared with some empirical expressions, having been located within the expected resistance range.