Flexural performance of RC beams with prefabricated steel reinforcement cage using mechanical sleeves

Based on ribbed steel bar direct rolling straight thread and the hot-forged double lock nut mechanical sleeve connection process, an innovative prefabricated reinforcement cage-cast-in-situ concrete (PRC-CISC) beam is proposed. Four groups of twelve reinforced concrete (RC) beams were fabricated with longitudinal bar strength, rebar connection methods, and loading modes as analysis parameters, to study their flexural behavior and the working performance of the rebar connectors (couplers). Firstly, the results show that all specimens exhibit typical bending failure modes, and the steel reinforcement cage connection method affects their failure morphology and causes the phenomenon of main crack migration. The load-deformation relationship, equivalent stiffness, and ductility of the PRC-CISC beams are similar to those of the reference specimens, indicating that the coupler's stress is reliable and the specimens have sufficient strength and stiffness. Furthermore, The mid-span deflection of all 4 groups of specimens at yield is less than 0.50 %, meeting the deformation requirements under normal service limit states. The strain in the mid-span of the PRC-CISC beams with full-section sleeve connections is much lower than that of the control specimens, indicating that the increase in effective tensile area of the sleeve reduces the stress it bears. Finally, the cracking behavior and stress mechanism of PRC-CISC beams are analyzed based on experimental research and theoretical models.