Abstract
The joints under study are the welded butt-type tube-to-gussetplate joints, in which a gusset passed through slits prepared at the tube end. These joints are frequently used as bolted field connections in transmission towers. Flange joints having an end plate at the tube end were also tested for comparison. It was found that fatigue lives of these joints were scattered around a single S-N curve, when nominal stress ranges were plotted against cycles to failure. However, differences in fatigue lives between the joint types were rather significant. A stronger correlation was observed between cycles to crack initiation and measured hot-spot strain ranges. A fatigue curve was estimated by means of the strain control concept using the fatigue notch factor, K_w that was to take account of geometrical discontinuities at the weld toes. This curve was found to represent the relationships between the cycles to crack initiation and the hot-spot strain ranges for various joints including cruciform joints with fillet welded gussets.
