Serviceability Moment Capacity of Bolted Endplate Minor-Axis Connections in Prefabricated Steel Frames: Role of Column Web Yielding and Numerical Verification

This paper aims to systematically investigate the out-of-plane yield performance, structural reliability, and sensitivity boundaries of minor-axis joints under construction overloads. To achieve this objective, a high-fidelity three-dimensional non-linear finite element framework incorporates precise solid continuum elements, contact non-linearities, and multi-linear material models, which is successfully validated against referenced experimental curves. Utilizing efficient Latin Hypercube Sampling integrated with response surface surrogate methodologies, a comprehensive stochastic parametric scanning is conducted to map the multi-dimensional scatter profiles and probabilistic capacity responses at targeted elastic thresholds. Furthermore, based on the upper-bound theorem of plasticity, closed-form analytical formulations defining the competition between independent and global plastic mechanisms are established and rigorously validated against extensive numerical parametric matrices. The core mechanical insights demonstrate that the column web thickness tw and column section depth b overwhelmingly dictate nearly 60% of the joint’s elastic-limit resistance by directly defining the out-of-plane bending span. While the divergence between the two competitive plastic mechanisms remains minute under severe flange constraints, the research uncovers a critical localized interaction: in connections with a relatively thick tw, the extended endplate thickness tep and endplate flexibility trigger a dynamic migration of the rotation axis between the longitudinal boundaries L0 and La, significantly shortening the effective internal lever arm. For practical design applications, calibrating these formulations with a partial safety factor γM = 1.25 successfully establishes a dependable lower-bound design strength, providing a verified safety red-line for temporary cantilevered scaffolding installations.