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Bolts tested on Canadian bridge following deck failure

Nipigon River Bridge Aerial View

Engineers have started testing bolts from the Nipigon River Bridge after it disconnected two weeks ago, less than two months after the new structure was opened to traffic.

Surface Science Western and the Faculty of Engineering at Western University and the National Research Council of Canada have been appointed to test the bridge’s bolts to try and establish the cause of the damage.

The bridge is in the process of a £54M reconstruction by a Ferrovial Agroman/Bot Construction joint venture and the damage happened on a section of road that had only opened in late November. It is understood that an expansion joint in the bridge deck failed, causing a deck section to rise by almost 0.5m. The bridge was immediately closed to traffic, severing the major east-west transport link through Ontario. By adding counterweights to level the bridge surface, authorities were able to re-open the bridge to one lane of traffic a few days later.

“This week, the labs will be completing an independent, visual ‎examination of the bolts,” said Ontario Minister of Transportation Steven Del Duca.

“Once that examination is complete, the two labs will be in a better position to determine how long the full testing will take. Full testing will include a chemical analysis of the bolts, a determination of the nature of the failure, a confirmation of the mechanical properties of the bolts as well as a comparison of the bolts to design specifications.

“We have expressed to both research labs that this testing is a top priority for our government, however, it is important that we get it right, and that will take some time.”

The bridge was designed by Canadian consultant MMM, which was acquired by WSP in August last year.

Del Duca said that the ministry continued to work with the enigneers involved plus engineers from Buckland Taylor in British Columbia who provided additional cable-stayed bridge expertise.

Del Duca said that it had been confirmed that the cables had been correctly tensioned and that the design was performed in accordance with the Canadian Highway Bridge Design Code, which takes into account local weather conditions

These require that the bridge is capable of withstanding winds in excess of 100 km/h and freezing temperatures well below -40ºC.

The aim is to re-open the bridge to two lanes of traffic by the end of February.

 

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