Analytical Modeling and Design Resistance of Axially Loaded CHS XX Joints

The design axial resistance for circular hollow section (CHS) XX joints is typically calculated as the product of the CHS X joint resistance and a multiplanar factor. A simple function has been used as the multiplanar factor, which is independent of the joint geometry parameters. In this study, it is first shown that the geometry-independent multiplanar factor does not properly reflect the true behavior of CHS XX joints, resulting in an overly conservative design for joints with large braces. Therefore, an analytical ring model is developed that more accurately captures the effect of the two important nondimensional geometric parameters, namely the brace-to-chord diameter ratio (beta) and chord diameter-to-thickness ratio (2 gamma). Subsequently, extensive test-validated numerical parametric analyses are performed, including a wide range of geometric and loading parameters, to propose an improved design resistance based on the developed analytical ring model. The formulated design resistance showed a better accuracy compared to the current code design resistance.