High-cycle fatigue behaviour of welded thin SHS-CHS T-joints under in-plane bending

Static tests of welded thin walled square hollow sections (SHS) and circular hollow sections (CHS) T-joints, under in-plane bending, have been used to produce load-deformation curves from which the maximum linear response moment of connection has been determined. The loads corresponding to the maximum linear response moment and below have been applied during cyclic loading and found to produce a high-cycle fatigue response in the SHS-CHS joints. A formula has been derived for predicting the ratio between maximum linear response moment and static strength as a function of the nondimensionaL parameters. The fatigue data of the welded thin-walled SHS-CHS T-joints was found to lie within the same scatter band as the S-N data of thin-walled SHS-CHS T-joints. An analysis of the S-N data of the thin-walled SHS-CHS T-joints shows that there is a minimal difference in the design curve obtained when the inherent scatter in fatigue data is taken into account.