Experimental Investigation and Calculation Method on Axial Compression Properties of Unbonded Prestressed Mortise–Tenon Precast Concrete Mid Joint

This study examines the axial compression performance of unbonded prestressed mortise–tenon beam–column joints (MTPC). The MTPC joint employs a mortise–tenon configuration, achieving tight compression through unbonded prestressed steel strands at the column's center, enhancing prefabrication efficiency. Three axial compression test models were fabricated and subjected to axial monotonic loading, with experimental phenomena and results analyzed. The results show the optimized MTPC joint achieves approximately 90% of the column‐end axial capacity, while MTPC joints reinforced with ultra‐high‐performance concrete (UHPC) surpass the column‐end capacity, fulfilling the “strong joints, weak components” design principle. Minor gaps during assembly require axial pressure for tight component contact, but the assembled joint demonstrates excellent integrity, stable axial stiffness, and effective load transfer. A calculation method for the axial load‐bearing capacity of MTPC joints is proposed, along with a finite element model. Comparison with experimental results validates the model's accuracy. Theoretical calculations, experimental data, and finite element analysis collectively confirm the proposed method effectively predicts the axial compression capacity and mechanical behavior of MTPC joints under axial loading. This research highlights the MTPC joint's potential for enhancing construction efficiency and structural performance in prefabricated systems.