Strength Capacity Characteristics of Welded and Mechanical Couple Spliced Steel Bars for Reinforcing Concrete

Abstract

Lapping, the commonest technique used to splice reinforcement bars, needs no special instrument or skill to execute. However, their usage may result in excessive section reinforcement, which may result in a non-ductile response of the spliced region. The structural performance of reinforcement bar splices plays a critical role in ensuring the continuity and load transfer capacity of reinforced concrete members. This study experimentally investigated the tensile behaviour of steel reinforcement bars connected using threaded couplers and welded joints, with particular emphasis on the influence of connection development length and bar diameter. Tensile tests were conducted on 12 mm, 16 mm, and 20 mm diameter reinforcing bars with threaded engagement lengths of d, 3d, and 5d, and weld lengths of end-to-end, 3d, 5d, and 7d. The results show that connection length significantly affects the mechanical performance of both joining techniques. For threaded couplers, the 12 mm bars exhibited substantial reductions in yield and ultimate strengths at short thread engagement (d), achieving only 29–37% of the control strength. However, increasing the thread length to 3d and 5d significantly improved performance, with the 16 mm and 20 mm bars nearly recovering the full strength of the control specimens. In welded connections, increasing the weld length resulted in substantial strength recovery, with welded bars at 5d and 7d achieving strengths comparable to or slightly exceeding those of the control bars. The findings demonstrate that both threaded and welded reinforcement connections can achieve mechanical performance comparable to continuous bars when sufficient connection development length is provided. However, their efficiency varies with bar diameter and connection configuration.