Tensile performance of eccentric flange joint for CHS steel tubes

This paper presents experimental studies aimed at proposing a refined design for eccentric flange-bolted joints in steel pipes. The proposed design involves the removal of the externally exposed flange to protect the external finishing material from potential damage. To assess the stability of the eccentric flange joint, a series of comparative specimens, comprising typical centric flange-plate (CFP) joints and eccentric flange-plate (EFP) joints, are meticulously manufactured and subjected to comprehensive tensile performance evaluations. A total of 42 specimens, consisting of 12 CFP joints and 30 EFP joints, are prepared, varying the thickness of the flange plate and the number of bolts. Specifically, flange plate thicknesses of 3.2, 4.0, 4.5, 6.0, 8.0, and 9.0 mm, as well as 3, 4, 5, and 6 bolts, were considered. The structural performance of the flange joints was thoroughly analyzed, taking into account parameters such as yield strength, tensile strength, stiffness, and failure mode. The study further encompasses theoretical calculations and finite element (FE) simulations to introduce eccentric-magnification factors (EM factors) that establish a clear relationship between CFP and EFP designs, while providing a comprehensive understanding of the behavior of the flange plate under tensile forces. Notably, the majority of cases exhibited increased yield strength and maximum strength as the flange plate thickness and the number of bolts were augmented. Moreover, the study proposes stiffness reduction values and flange EM factors through a meticulous comparison of experimental and theoretical results. While acknowledging that these factors were derived from detailed guidelines that account for minimal edge clearance, the proposed flange joint design, characterized by its commendable tensile performance, offers valuable insights for future design guidelines.