Technology Digests / Long-Term Testing of Ultrasonic Impact Treatment for Steel Bridge Weld Details

TD22-010

June 1, 2022
Authors
  • Duane Otter
  • David Linkowski
  • Chris Johnson
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Key Findings

  • A long-term study has shown that ultrasonic impact treatment (UIT) may be a cost-effective method of extending the life of steel bridges with certain types of fatigue-prone weld details.
  • The UIT of weld toes was somewhat effective in reducing the likelihood of and/or delaying the occurrence of crack initiation in pre-existing, fatigue-prone weld details in the tested bridge.
  • Since the original installation, the UIT application procedures have been refined to treat more of the weld and surrounding material and provide improved benefits overall.
  • Using weld repairs to address fatigue cracks, in conjunction with the refined UIT process, has the potential to extend the life of steel bridges with certain types of fatigue cracks.
  • In 11 years of inspections during the MxV Rail study, there have been no cracks in treated repair welds.

Long-Term Testing of Ultrasonic Impact Treatment for Steel Bridge Weld Details

From 2005 to 2020, MxV Rail (formerly TTCI) monitored the performance of an ultrasonic impact treatment (UIT) application to fatigue-prone weld details on a 16-span steel bridge in revenue service. Two long-term tests were used to study the effectiveness of UIT in reducing fatigue cracking in certain welds. In 2005, MxV Rail evaluated the use of UIT to prevent fatigue crack initiation in existing (shop-welded) fatigue-prone weld details. After showing positive preliminary results, a study initiated in 2009 evaluated the effectiveness of UIT on field-welded crack repairs. Positive results from previous studies1–3 suggested the need for a field study with a large number of details to provide statistical significance. This Technology Digest describes the results of the long-term field tests on a revenue service steel bridge with more than 200 weld details. With steel railroad bridges aging and axle loads increasing, bridge component fatigue has become a concern for railroads.…