Fatigue assessment of welded joints in tubular structures in industrial applications according to the current design codes is based on the block-type presentation of the loading histories. An approximate procedure of the long-term stress distribution transformation to the block-type format is developed. It allows reducing the number of equivalent cyclic stress fragments compared to those required by the rules for fatigue design and provides ac-curacy of fatigue analysis of tubular frame structures. Efficiency of the developed approach is illustrated in example of fatigue assessment of the tubular frame bridge structure. Technique of analysis may be used to choose sufficiently reliable versions of the detail.