Splice Strength of Reinforcing Bars with High and Low Alternating Ribs

Abstract

This paper describes an experimental analysis of 41 beam specimens conducted to investigate the splice strength of reinforcing bars in a novel alternating high and low rib pattern. The newly developed reinforcing steel bars have equally spaced, alternating high and low ribs. The variables in the experiment are the reinforcing bar size-D19, D22, D25, and D29 (No. 6, No. 7, No. 8, and No. 9); the relative rib area (R-r), ranging from 0.065 to 0.140; the reinforcing bar position-top-cast reinforcing bar or bottom-cast reinforcing bar; the degree of confinement provided by transverse reinforcement; and the different deformation patterns, including conventional, high relative rib area, and alternating high and low rib-reinforcing bar structures. The experimental results demonstrate that splice strength from an alternating high and low rib reinforcing bar pattern with confinement is 34% higher than that from a conventional reinforcing bar pattern. Furthermore, the splice strength of an alternating reinforcing bar pattern without confinement is 18% higher than that of a conventional reinforcing bar pattern. Using these results and further investigation, it is confirmed that the developed alternating high and low rib-reinforcing bar pattern (R-r of 0.130) with confinement gives the possibility of reducing splice length by a maximum of 45% compared to a conventional reinforcing bar pattern (R-r of 0.072). The reduction in splice strength of a top-cast reinforcing bar relative to a bottomcast reinforcing bar using this alternating deformation pattern is 16% lower than that found in bars with conventional deformation. Based on our analysis, an expression is proposed to define R-r for bars with this kind of alternating deformation. Also, a design procedure to calculate the splice and development length of bars with alternating ribs is suggested.