Shear Strength of Conventional and Lightweight Concrete I-Beams with Fibrous Webs

Abstract

This study investigates the behavior of the shear strength of fibrous concrete I-beams made from normal and lightweight concrete that have the same compression strength, of about 30 MPa. Lightweight aggregate concrete was made by replacing 75% of the coarse aggregate with lightweight aggregate (Bonza stone). Fourteen concrete I-beams with dimensions of 1000×210×175 mm were divided into two groups. In the first group, the web area was reinforced with steel fiber added in 0.5%, 1%, and 1.5% of the mix volume. The second group was reinforced with glass fiber added in the same percentage as the steel fiber. The results showed that the shear strength of a Normal Concrete Beam with Steel Fibers (NCSF) is increased by 3.5%, 13.5%, and 13.3% for the addition ratios of 0.5%, 1%, and 1.5%, respectively, compared to the Normal Concrete Beam without Fibers (NC). Webs with glass fibers gain an increase of about 3.7% and 14.05% for the addition ratios of 0.5% and 1%, respectively, while the shear strength decreased by 6.21% for the addition ratio of 1.5%. On the other hand, the Lightweight Concrete Beam with Steel Fibers (LWCBSF) achieved greater shear strength than the Lightweight Concrete Beams without Fibers (LWCB) by 4.8%, 13.5%, and 10.9%; for the three additional percentages, respectively. The shear strength increased by 8.4% and 11.04% for the Lightweight Concrete Beam with Glass Fibers (LWCBGF) at 0.5% and 1% ratios, while the shear strength decreased by 11.9% for the 1.5% glass fibers ratio compared to the Lightweight concrete Beam without Glass Fibers (LWCB). The best performance, according to the ultimate load, was achieved when fibers were added at a ratio of 1% in normal and lightweight concrete compared to other ratios.