Experimental study on axial compression performance of mortise-and-tenon precast concrete beam–column joints

Mortise-and-tenon precast concrete (MTPC) beam–column joints utilize a mortise–tenon structure with longitudinal prestressing to secure their connections. This approach offers advantages such as dry construction, easy assembly, a short construction period, and the possibility of disassembly. To meet the “strong joint” requirement, this study enhances the core areas of the joints through ultra-high–performance concrete (UHPC) reinforcement and rebar enhancement. First, the structure and assembly method for MTPC joints are introduced. Subsequently, five distinct specimens are fabricated for testing: two UHPC-reinforced models, one rebar-enhanced model, one standard MTPC joint model, and one cast-in-place joint model. All specimens are then subjected to monotonic axial compression tests. The results show that the optimized MTPC joints exhibit significantly improved axial compressive strength, reaching 90% to 100% of the capacity of the cast-in-place joint. With regard to the optimization methods, whereas increasing rebar ratios enhances axial strength, it does not fully achieve the “strong joint” criterion. By contrast, UHPC reinforcement significantly boosts axial compressive capacity, achieving the desired “strong joint” standard. After axial load is used to compact the assembly gaps in MTPC joints, the overall integrity is made strong, axial stiffness remains stable, and the load transfer path becomes clear. With UHPC reinforcement, force transmission through the MTPC joint components becomes more reliable, with the tenon bearing more axial load; however, the tenon should not be used as the main vertical force transmission section. Finally, it is found that the axial compressive load capacity calculation method recommended by the Chinese code can accurately and safely predict the axial compressive load capacities of MTPC joints.