Fatigue behaviour of welded CHS bridge joints: emphasis on the effect of size

Welded CHS joints typical to the bridge application have been examined in an experimental and numerical study Evidence from this study has indicated lower fatigue strength for joints with thicker failed members. This phenomenon - generally referred to as the size effect - is reflected in design specifications, where a substantial penalty is applied to welded CBS joints with increasing wall thickness' A re-examination of the data on which the size effect correction in current specifications is based has raised questions about its validity, especially for joints with greater wall thicknesses. Fatigue lives of welded CBS K-joints have been calculated based on LEFM methods. Results have shown that the relative fatigue strength of these joints as affected by changes in wall thickness, joint scale and loading produce a so-called size correction that is substantially different than that in the specifications.