United States Department of Transportation
i
Investigation of delayed cracking in pivot steel box girders.
-
1997-01-01
[PDF-4.82 MB]
Details:
-
Creators:
-
Corporate Creators:
-
Subject/TRT Terms:
-
Publication/ Report Number:
-
Resource Type:
-
Geographical Coverage:
-
Edition:Final report.April 1996June 1997.
-
Corporate Publisher:
-
Abstract:This report describes the results of an investigation to find the cause of the delayed cracking in the welds of the fracturecritical steel pivot box girders fabricated for the George P. Coleman Bridge. Through the use of different nondestructive methods, more than 200 transverse and longitudinal cracks were found. The possibility of unique, rare, and very long-term delayed cracking (cold or hydrogen-induced cracking) was supported by the results of the hydrogen content analysis, residual stress measurements, and macro-microstructural metallography and fractography. There was strong evidence that a susceptibility to hydrogen-induced cracking of the weld metal in the north girder developed during fabrication and that this susceptibility, the presence of hydrogen in the weld and base metal, and residual stresses combined to cause cracking to occur. The great number of cracks detected in the welds of the north girder, coupled with the very large total crack lengths, demonstrated that these welds have been and still are inordinately susceptible to cold cracking. Calculations showed that brittle fracture could occur in the partial penetration groove weld under the worst conditions, but this is not probable. Calculations also showed that there is little probability that the cracks will extend in any significant amount because of fatigue during the life of the bridge. The author recommends that the north box girder be inspected by magnetic particle testing or eddy current testing at least every 6 months for the next 3 years and that cracks be repaired when found.
-
Format:
-
Collection(s):
-
Main Document Checksum:
-
Download URL:
-
File Type:
