Structural performance of splice sleeve connector with vertical and spiral reinforcement bar under direct tensile load

A splice sleeve connector is used to splice two reinforcement bars with their ends aligned adjacently, ensuring continuity in load transfer between them. Its tensile resistance relies on the interactions among reinforcement bars and bonding material. In this study, a series of twenty seven splice sleeve connectors with vertical and spiral reinforcement bars were tested under incremental tensile load until failure. The proposed specimens were different between each other in terms of quantity of vertical bars used and diameter of spiral. They were provided to resist the grout from slipping out of the sleeve. Their performance under direct tensile load was evaluated based on the load-displacement relationship, ultimate loading capacity, displacement and failure mode. Basically, four modes of failures were observed through the testing; (1) bar fractured, (2) bar slippage (3) grout fractured and (4) bar slippage and grout fractured as bond failed. The results show that the specimens with three and four vertical bars were better than the specimens with two vertical bars. Despite of providing interlocking effect to resist the grout from slipping out of the sleeve, these spiral and vertical bars also responded to the inclined stress that was generated due to force diversity caused by the splice bar, inducing excessive compressive stress to the sleeve connector. From the load-displacement curves and failure modes, eighteen of the specimens presented satisfactory result because of the long development length and the configuration of spiral and vertical bars had created more confinement effect to keep the grout and reinforcement intact. Finally, the understanding of the causes of failure obtained from the study provided essential information for further study in developing more reliable splice sleeve connector.