Experimental Study and Numerical Modeling of the Lap Strength of Reinforcing Steel Bars Milled from Recycled Scrap Metals

Abstract

The study aimed to assess the lap strength of reinforcing steel bars milled from scrap metals in beams. Lapping of reinforcing bars is generally inevitable in concrete members such as beams, slabs and columns due to construction dictates and such bars are required to effectively transfer stresses between them. The study explored the influence of different lap lengths on structural performance, considering variables such as rebar diameter and spliced length. Experimental work was carried out involving both four-point load bending (4PB) and three-point load bending (3PB) on twelve (12) reinforced concrete beams with varying lap lengths. The reinforcing steel bars ranged from 10mm to 20mm in diameter. The experimental setup included measurements and testing of the bars' yield and ultimate stresses, as well as the preparation and curing of concrete specimens. Findings indicated that larger reinforcing bars and longer lap lengths had enhanced load-carrying capacity and stiffness, and also longer lap lengths reduced deflections. The research contributes insights into suitable lap strength, crack behavior, and failure modes in reinforced concrete beams, offering valuable recommendations for improved design practices. Finite Element Analysis of the beams was conducted by modeling them into ABACUS and validated with the experimental results. The findings from FEM confirm that longer lap lengths enhance load transfer and stiffness, and larger diameter bars improve load-carrying capacity and stiffness. The study concludes with recommendations for good design option, highlighting on longer lap lengths and the use of larger diameter bars for lapping. Additional recommendations include ensuring adequate shear reinforcement (stirrups) to prevent premature shear failure.