Key technologies for applying Q690qE TMCP high-strength steel in bridge engineering

The Q690qE TMCP high-strength steel exhibits a very fine and uniform acicular ferrite microstructure. Under welding conditions that reach fusion temperature, it undergoes significant metallurgical changes, making TMCP high-strength steel more sensitive to welding procedures than mild steels. Furthermore, to fully utilize the steel’s high strength and reduce structural deadweight, lighter cross-section designs are typically employed, which increases the susceptibility of bridge structures to local buckling. Therefore, this study investigates the fatigue strength of welded joints and the local buckling strength of stiffened plates. The findings reveal that: (a) the fatigue strength of welded joints fabricated with high-strength steel is significantly lower than the values specified in design codes if non-standard welding procedures are employed. The primary cause of the reduced fatigue strength in these specimens is cracks induced by the non-standard welding procedures; (b) the reduction factor for local buckling specified in the Chinese standard, Specifications for Design of Highway Steel Bridge, is excessively conservative. In contrast, the reduction factor provided in the European code EN 5 January 1993, which accounts for the post-buckling behavior of the compression plate, offers a more accurate prediction of the plate’s buckling strength when considering only local buckling.