EXPERIMENTAL INVESTIGATION OF THE PERFORMANCE OF FIBROUS REINFORCED CONCRETE DEEP BEAM WITH VARIOUS SIZE OF SQUARE WEB-OPENING

Abstract

This study aims to experimentally investigate the performance of steel fiber-reinforced concrete deep beams with various sizes of square web-opening applied to shear and shear-bending control loading scenarios. Twelve specimens were distributed to two groups according to loading control (shear & shear-bending). Each group consist of three beams prepared of fibrous concrete and others prepared of normal concrete. The three specimens consists of one that is solid as a reference and others containing various-sized square web openings (200 mm & 300 mm). The test results show that all the tested beams failed as shear failure except for the solid beams under shear-bending control, which failed as flexural failure. The presence of square openings with sharp corners and edges leads to high stress concentration, especially when these openings are located in the natural load transmission path. Steel fibers maintain the linear behavior in deep beams with openings until late loading stages, as evident in load-deflection curves. Fibrous beams with openings remained nearly identical. Unlike normal concrete beams, there was a large difference in the load-deflection curves since the early stages of loading. The tested beams failed after yielding of steel reinforcement, as the steel strain of fibrous specimens was lower than that of normal concrete. Steel fibers contributed to reducing stresses in reinforcing steel. Fibrous beams exhibit higher stiffness than normal beams, largely due to the presence of steel fibers. These fibers provide additional tensile strength, resisting shear cracks. Additionally, fibers increase the ductility index and absorption energy, redistributing stresses and provide warning before failure