Welder-optimized CJP-equivalency welds for tubular connections

This paper will present the experimental and numerical investigation on the fatigue crack failure at the root of the enhanced partial joint penetration welds in the circular hollow section X-joint specimens subjected to constant-amplitude brace in-plane bending actions. The enhanced partial joint penetration welds, which include a portion of the brace wall as the inherent “back-plate” for the welds, reduce the workmanship requirement on the welding procedure and improve the quality control of the welded joint. This study compares the fatigue crack developments observed at both the weld toe and the weld root in three large-scale X-joint specimens with different post-weld surface treatments. Root cracking does not take place in as-welded tubular X-joint specimens, of which the fatigue life depends on the weld toe failure. In specimens with post-weld grinding treatments to enhance fatigue resistance of the material near the weld toe, however, the finite-length root face triggers the initiation and propagation of fatigue cracks with an applied number of cycles more than that required to initiate a toe crack in the same tubular X-joint. Ultimate strength testing of specimens with large fatigue cracks, and post-test sectioning, reveals that fatigue failure weld-toe fatigue cracks remain more critical than the root cracks.