Degree of bending in steel tubular T-joints with concrete-filled chords subjected to axial loadings

Through-the-thickness stress distribution in a tubular member has a profound effect on the fatigue behavior of tubular joints commonly found in steel offshore structures. Such stress distribution can be characterized by the degree of bending (DoB). Although tubular T-joints with concrete-filled chords are commonly used in offshore tubular structures and the concrete fill can have a significant effect on the DoB values at the brace-to-chord intersection, no investigation has been reported on the DoB in tubular T-joints with concrete-filled chords due to the complexity of the problem and high cost involved. In the present research, data extracted from 162 stress analyses conducted on 81 finite element (FE) models subjected to brace tension and compression, verified based on available experimental data and parametric equations, was used to study the effects of geometrical parameters on the DoB values in tubular T-joints with concrete-filled chords. Parametric FE study was followed by a set of nonlinear regression analyses to develop four new DoB parametric equations for the fatigue analysis and design of axially loaded tubular T-joints with concrete-filled chords.