Abstract: Full-scale test modules are prepared to examine the mechanical performance of U- and V-shaped connection nodes of longitudinally distributed reinforcement in prefabricated reinforcement cage modules used in open-cut station structures. Indoor tests on bending-shear and double-point bending provide data on bending moment, strain, and crack development. The mechanical performance of U- and V-shaped lapped joints in prefabricated reinforcement cages of open-cut metro stations under pure bending and combined bending-shear loading conditions is investigated and compared with continuous reinforcement joints as a benchmark. The experimental results reveal the crack propagation patterns, material strain responses, and load-bearing characteristics of the different joint types. Key findings are as follows: (1) Under the pure bending condition, continuous reinforcement joints display ductile behavior, with a bending moment capacity increasing by 81.3% from crack onset (675 kN·m) to the ultimate state (1 224 kN·m), accompanied by an ultimate deflection of 12.1 mm. V-shaped lapped joints reach 80.2% (982 kN·m) of the ultimate bending capacity of continuous joints and show a comparable ultimate deflection of 11.94 mm. U-shaped lapped joints exhibit brittle failure behavior, with only a 31.7% strength increase (from 575 to 757 kN·m) and minimal deformation prior to failure. (2) Under the combined bending-shear loading condition, continuous joints maintain the highest ultimate bending moment (1 275 kN·m) and stiffness control, with a deflection of 7.5 mm. V-shaped joints complete full deformation cycles, reaching an ultimate deflection of 13.17 mm and 77.3% of the ultimate bending capacity of continuous joints. U-shaped joints experience early cracking at 775 kN·m, followed by strength stagnation, resulting in a final deflection of 6.8 mm, equivalent to 54.7% of the continuous joints′ capacity. (3) Comprehensive comparative analysis demonstrates that the V-shaped lapped joints exhibit significant performance advantages over U-shaped joints, achieving 82% of the ultimate load-bearing capacity, 85% of the ductility coefficient, and better failure control when compared to continuous joints. Therefore, V-shaped lapped joints are recommended as the preferred solution for connecting longitudinally distributed bars in prefabricated reinforcement cages.

Key words: open-cut metro station, prefabricated reinforcement cage, U-shaped lapped joints for distributed reinforcement bars, V-shaped lapped joints for distributed reinforcement bars, mechanical properties of joint