Fatigue Performance of High-Frequency Welded Steel I-Beams

CONCLUSIONS

This research was performed to develop preliminary fatigue design recommendations for the use of HF-welded steel I-beams in bridge design. The HF welds were used in joining the web and flanges of the I-beam. Historical fatigue data have found longitudinally loaded web-to-flange welds are category B details, whether joined by fillet or CJP welds.^{( 4 )} The lower bound of the three HF welds was less than category B, indicating HF welds have lesser fatigue strength than conventional welds. However, a statistically significant pool of HF weld failures is needed to more confidently make this conclusion.

Future work should consider removal of the flash from the web–flange junction after completion of the HF welding fabrication process. The three HF weld failures originated from the flash, and removing it could eliminate flaws and possibly increase the fatigue resistance. Furthermore, strict adherence to fabrication tolerances may provide benefits. Fabrication tolerances for the specimens tested in this research were questionable in some instances with regard to the perpendicularity of the web–flange junction. In some instances, this led to lateral instability issues during testing. Lastly, the beam sections tested were quite small, with a total depth of approximately 16 inches and flange thickness of 0.35 inch. Typical bridge designs use much larger sections, and additional testing should also be performed to ensure there are not scale effects.

REFERENCES

1. AASHTO. (2014). AASHTO LRFD Bridge Design Specifications. 7th ed. American Association of State Highway and Transportation Officials, Washington, DC.
   
   
2. ASTM Standard A769/A769M. (2010). “Standard Specification for Carbon and High-Strength Electric Resistance Forge-Welded Steel Structural Shapes.” Book of Standards Volume 01.04. ASTM International, West Conshohocken, PA.
   
   
3. ASTM E 8/E 8M-08. (2008). “Standard Test Methods for Tension Testing of Metallic Materials.” Book of Standards Volume 03.01. ASTM International, West Conshohocken, PA.
   
   
4. Keating, P.B. and Fisher, J.W. (1986). Evaluation of Fatigue Tests and Design Criteria on Welded Details, Report No. 286, National Cooperative Highway Research Program, Transportation Research Board, Washington, DC