Fatigue Behavior of T-Joints: Square Chords and Circular Braces

Abstract

Hollow sections are generally either circular-to-circular (CCHS) or rectangular-to-rectangular (RRHS). Structures with circular braces and rectangular chords (CRHS) may have advantages in certain applications, combining a simple joint geometry for fabrication and relatively lower stress concentration factors (SCFs). Seven different CRHS joints were fatigue tested in constant amplitude axial loading. SCFs were measured experimentally and compared with various parametric formulas. The SCF values for CRHS joints were found to be between those of CCHS and RRHS joints. On the basis of measured SCF values for CRHS joints, the fatigue strength was in good agreement with current fatigue design codes. Parametric formulas for RRHS joints were in all cases found to give conservative prediction of SCF. Lacking more rational prediction methods, these formulas in combination with the DEn T curve/AWS X2 curves for tubular joints may be used in fatigue design of CRHS joints.