Axial tensile performance of a novel self-locking plug-in and unlockable inter-module connection for modular steel buildings

Inter-module connections are critical to the structural performance and construction efficiency of modular steel buildings, while existing self-locking connections often involve complex mechanical components and stringent fabrication or assembly requirements. This study proposes a novel self-locking and plug-in and unlockable (SLPU) inter-module connection featuring rapid assembly, convenient unlocking, and tolerance to fabrication deviations. The feasibility of the self-locking and unlocking mechanisms was first verified through assembly tests, followed by axial tensile tests on three full-scale specimens to investigate the tensile behaviour and load-transfer mechanism. All specimens failed by shear fracture of the trapezoidal protrusions of the sliding blocks, while the main connection components remained essentially undamaged. Increasing the sliding-block thickness from 16 to 20 mm increased the ultimate tensile resistance by approximately 28%. Refined finite element (FE) models were then developed and validated against the experimental results. The analyses revealed that fabrication deviations mainly affected the engagement sequence and local load-transfer behaviour of the protrusions, while having a limited influence on the overall failure mechanism. Parametric analyses further identified the sliding-block thickness and chute base-plate thickness as key parameters governing the tensile resistance and failure-mode transition of the connection. Based on the identified load-transfer mechanisms and potential limit states, an analytical method was developed to predict the tensile resistance of the SLPU connection. The predicted resistances agreed well with the experimental and FE results. The proposed connection and analytical method provide a practical basis for the design and application of self-locking inter-module connections in modular steel buildings.