Investigation and Repair of the Diefenbaker Bridge Fracture
Bibliographic record
Abstract
The Diefenbaker Bridge is a 7-span, 304m (1000 ft) long, fracture critical steel structure crossing the North Saskatchewan River in Prince Albert, Saskatchewan, Canada, constructed in 1959. On August 29th, 2011 a major fracture was found in one of the two steel girders of the southbound bridge. The crack extended from the bottom flange through the web of the girder, nearly full height of the girder and is one of the largest in-service bridge fractures to occur in Canada. The southbound structure was immediately closed and traffic was diverted to the parallel northbound structure. This paper describes the resulting fracture investigation and major structural repair implemented on the structure. Based on this investigation, the structure is believed to be susceptible to constraint-induced fracture (CIF). To repair the structure, the fractured bridge was supported on steel towers constructed on a river berm and raised to its original position. A section of the girder was then cut out and replaced with new steel and connected to the temporarily supported horizontal and vertical bracing. Once the structure was reopened to traffic, attention was turned towards rehabilitation including retrofit methods to mitigate approximately 160 CIF susceptible details in the southbound and northbound structures. The methods used to retrofit the CIF details are described along with lessons learned. The paper will be of interest to bridge owners, designers, and anyone involved in inspecting and maintaining bridge infrastructure. For the covering abstract of this conference see ITRD record number 201310RT334E.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".