Inspection and Management of Bridges with Fracture-Critical Details (2005) / Chapter Skim
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Pages 24-30
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From page 24... ...
Specifically, the survey was intended to collect data in varying levels related to the following: • How FCMs are presently defined, documented, and managed; • Inspection frequencies and procedures; • Methods for calculating remaining fatigue life; • Qualification and training of inspectors; • Available and needed training; • Locally owned bridges; • Experience with FCM fractures and problem details; • Examples of where an inspection program prevented failures; • Cost of inspection programs; • Retrofit techniques used; • NDE methods used; • As-built versus as-designed; • Fabrication methods and fabrication inspection; and • Impact of staff turnover. BACKGROUND A detailed questionnaire intended to identify and characterize specific issues related to FCBs was developed and distributed to all state and Canadian provincial DOTs and various other transportation authorities within the United States.
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From page 25... ...
Fortunately, the loading used for fatigue design and the analytical models were, in most cases, quite conservative. FCBs designed beginning in the early 1980s were detailed to minimize out-of-plane distortion cracking and minimize the use of low-fatigue resistance details (D, E, and E′)
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From page 26... ...
As stated, some agencies inspect FCBs more frequently than non-FCBs. As part of the survey, owners were asked to provide the intervals at which inspections are conducted.
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From page 27... ...
, the Hoan Bridge (38) , and other bridges with shelf–plate details for lateral bracing that were not built as shown in the plans and were not the same quality welding as expected.
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From page 28... ...
With respect to fatigue, it is commonly observed that by using simplified structural analysis methods the calculations for many bridges indicated no remaining fatigue life or even "negative" fatigue life. These calculations imply that fatigue cracking should be observed presently or in the near future on these bridges.
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From page 29... ...
(A bridge posted for 3 tons that has collapsed because a 30-ton truck attempted to cross it did not fail simply because it was fracture-critical.) Rather, the data suggest that there are very few failures that have been caused by fatigue or brittle fracture in the absence of overloads, impact, scour, or corrosion.
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From page 30... ...
One is the Point Pleasant Bridge that failed before any initiatives related to the FCP and NBIS. The second is the Mianus River Bridge, which failed before the implementation of the FCB inspection program.
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