Details:

Creators:
Huckelbridge, Arthur ; Metzger, Andrew
Huckelbridge, Arthur ; Metzger, Andrew Less -
Corporate Creators:
Case Western Reserve University. Department of Civil Engineering
Corporate Contributors:
Ohio. Dept. of Transportation. Office of Traffic Engineering
Subject/TRT Terms:
[+]
Failure Failure Analysis Field Studies Field Tests Inspection Sign Supports Structural Analysis Testing Trusses Vertical Supports Welds Weld Strength
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.


Format:
PDF
Funding:
ODOT Agreement Number 14237
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:f7940fa10cf4de524e657973f4d1da8cbc5999e1e666fb82665a922d5995077f
Download URL:
https://rosap.ntl.bts.gov/view/dot/17546/dot_17546_DS1.pdf
File Type:

Supporting Files

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