Shear capacity of reinforced concrete beams with recycled steel fibers

Abstract

This study investigates the effect of using recycled steel fibers (RSFs) extracted from cut tires with dimensions of 0.8 and 40 mm in diameter and length, respectively. Different percentages of fibers were used, which are 0.5, 1, 1.5, and 2%. Ten beams with dimensions of 150 mm × 240 mm and a length of 1,700 mm were tested, two of which are control beams without stirrups and using stirrups at a distance higher than the upper limit (d/2), which is a distance of 250 mm. In the case of using steel fibers without a stirrup, it is noticed that shear resistance increases gradually, but the type of failure remains shear. When using a minimum stirrup with steel fibers, the shear resistance increased significantly by 11.1, 23.7, 33.3, and 41.4%, respectively, compared to the reference beam without steel fibers so that the increased shear capacity in the presence of the minimum stirrups and optimal ratio of steel fibers of 2% reaches 122%, compared to the reference beam without stirrup and steel fibers, as well as converting the type of failure from shear failure to pure bending failure. When using a stirrup, this effect will be greater. The presence of RSF reduces deflection at cracking load, while increasing deflection at the ultimate load. Therefore, the stiffness and ductility ratio increased with the presence of steel fibers by 41.5 and 50.3%, respectively. Also, steel fibers delayed the appearance of beam cracks and reduced their widths.