Evaluation of Ductility Index of a Rectangular Beam Reinforced with Rebars Milled from Scrap Metal

Abstract

Ductility index is essential both in structures and structural elements in service. Its inadequacy may lead to brittle failure and jeopardize the lives of occupants. In reinforced concrete beams that experience large inelastic deformation in service, its ductility index cannot be over- emphasized. In Nigeria, the steel sector is now sustained through the recycling of scrap metal obtained mainly from municipal solid wastes which find application in the construction Industry. The study evaluated the ductility index of a rectangular concrete beam reinforced with rebars milled from scrap metal. This was achieved by designing the beam, produced samples and assessed its behavior under load experimentally and analytically with emphasis on the deflection ductility index. Eighteen (100 mm x 200 mm x 1000 mm) concrete beams reinforced with rebars milled from scrap metal were produced; six each with concrete strength of 20.33, 26, 30 N/mm2 and steel ratio (ρ) of 0.0058 to 0.012 respectively. The samples were tested under a four- point loading and analyzed using the Hognestad models for concrete and steel, theoretical equations of strain compatibility and equilibrium of forces at the beam section. Based on the test data obtained in the laboratory and analytical approach, the failure mode of most beams was classified as ductile flexural failure accompanied by yielding of the tension steel preceding the crushing of concrete. The flexural capacity of the test samples ranged from 43.25 to 88.25 Kn with a deflection ductility index of 1.72 to 2.80. The analytical load-deflection relationship compared with experimental values show good agreement. This confirms the applicability of the theoretical approach which provides a useful tool for evaluating the deflection ductility index and load-deflection response of concrete rectangular beams reinforced with rebars milled from scrap metal. Key words: Ductility index, concrete beams, Rebars, scrap metal, deflection response.