ABSTRACT
Welded thin-walled (t<4mm) T-joints made up of circular hollow section (CHS) chords and braces were tested under cyclic in-plane bending. Surface crack growth was monitored and recorded for different stages of failure, namely first visual crack life (N2), through thickness crack life (N3) and end of test fatigue life (N4). The investigation shows that for thin-walled CHS-CHS T-joints, a through thickness crack occurs when the surface crack length has grown to about 40% of the circumference of the brace member. At the occurrence of a through thickness crack, the cracks have a small aspect ratio (a3/c3) ranging between 4.6% and 8.7%. An end of test failure criterion used in this investigation produces values of N4 that can be used instead of N3 values, in the determination of fatigue design curves if the inherent scatter associated with fatigue life is taken into account.
