Investigation of the Dayton IR 75 sign truss failure of 9/11/06.

Details

• Creators:
  Huckelbridge, Arthur ; Metzger, Andrew
• Corporate Creators:
  Case Western Reserve University. Department of Civil Engineering
• Corporate Contributors:
  Ohio. Dept. of Transportation. Office of Traffic Engineering
• Subject/TRT Terms:
  • Field studies
  • Field tests
  • Inspection
  • Sign supports
  • Vertical supports
  • Trusses
  • Failure
  • Failure analysis
  • Structural analysis
  • Testing
  More +
• Resource Type:
  Tech Report
• Geographical Coverage:
  Ohio
• Corporate Publisher:
  Case Western Reserve University. Dept. of Civil Engineering
• Abstract:
  Based upon a combination of in-situ field monitoring of traffic-induced bridge ; vibrations at the location of the failed sign support truss, finite element simulation of the ; expected dynamic response of the original truss in such an environment, the length of ; service of the truss at the time of its failure, the volume of truck traffic on the bridge in ; question during that time of service, and metallurgical examination of the failed ; components of the sign truss, the conclusion of the investigation is that extremely high- ; cycle fatigue of the chord/web diagonal welded connection was the cause of the truss ; failure. The in-service effective stress range of the AASHTO Category ET connection in ; question was most likely below the currently specified AASHTO constant amplitude ; fatigue limit (CAFL) for the detail, but the enormous quantity of response cycles ; (approaching or even exceeding 1 billion cycles) such a bridge mounted sign on a ; heavily traveled route accumulates over a service lifetime of 30 or 40 years, exceeds ; anything currently considered in the design codes for such structures. The implications ; of this fact on the current inventory of such structures in similar installations and of the ; same age range, i.e., installed with the original interstate routes, largely in the 1960’s, ; are obvious. ; The one somewhat puzzling aspect of the lower chord fracture of this structure, ; namely that the fracture passed near the weld toe but not actually contacting the weld ; toe, does not appear to be particularly significant. The fracture did indeed pass close to ; the weld and certainly within the heat affected zone of the weld. The fracture surfaces ; were too abraded to positively identify the initiation point; small cracks, however, were ; also identified within the weld under microscopic examination. The original flaw which ; eventually propagated and produced the rupture, apparently in this case, just happened ; to be near the weld rather than in the weld.
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• Format:
  PDF
• Funding:
  ODOT Agreement Number 14237
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/17546/dot_17546_DS1.pdf
• File Type:
  [PDF - 3.90 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:f7940fa10cf4de524e657973f4d1da8cbc5999e1e666fb82665a922d5995077f