Canada Has Been Cut In Half!

[aczlan]

This thing is confusing to me. They say the bridge lifted 60cm and shifted to one side, and it was closed. Later articles say they have 1 lane open to cars for now until they can tell if it can handle trucks. Was that lift and shift temporary, and now it's moved back into place?

From what I have heard guessed, the cables going to the top were too tight, so when it got cold and the cables tightened lifting the deck up. When a gust of wind came through, it was enough to break the bolts holding the bridge down.

Aaron Z

 

[Ford850]

From what I have heard guessed, the cables going to the top were too tight, so when it got cold and the cables tightened lifting the deck up. When a gust of wind came through, it was enough to break the bolts holding the bridge down.

Aaron Z

I'm talking more about it's state currently, not how it happened. Did it call back into place now? I can't understand how it is partially open if it is shifted off it's base.

 

[aczlan]

I'm talking more about it's state currently, not how it happened. Did it call back into place now? I can't understand how it is partially open if it is shifted off it's base.

They put 110 4800# jersey barriers on one side to weigh it down. That points strongly to the cables being too tight.

(Source: Nipigon River Bridge bolts undergo testing to see why they snapped - Thunder Bay - CBC News )
Also, its on rollers and its designed to move some with frost heaves.

Aaron Z

 

[Egon]

The rollers are to account for expansion/contraction of the bridge.

 

[RobS]

From the pics I've seen, it looks like it lifted and shifted sideways. The expansion joint likely prevents it from just slipping back into place (like a zipper that has been offset). One edge may sit near grade level but the other looks like it was raised up, probably on a piling or something. They may be letting light traffic pass on the lane that is close to grade level. I imagine the weight of a few cars is insignificant to such a bridge but a bridge full of loaded trucks may be something entirely different! No knowledge here, just speculating...

 

[California]

The rollers are to account for expansion/contraction of the bridge.

Sounds similar to the earthquake damage in 1989 at the San Francisco / Oakland Bay Bridge. That bridge didn't break, but rather, during the earthquake the distance from San Francisco to Oakland momentarily increased more than a foot, exceeding the length of one expansion joint. So the upper roadway fell into the lower roadway.

That damage was relatively simple to patch back together. However since this bridge will be the principal escape route from the San Francisco peninsula after the Big One hits, a whole new structure claimed to be far more earthquake tolerant has how replaced that segment of the bridge. As the replacement was completed, problems in the new bridge became apparent similar to your Nipigon Bridge - huge bolts embedded in the columns snapped off deep in the concrete when they bolted down the deck (fix cost $25 million), suspension cables and inaccessible crawlspaces already had unacceptable corrosion, and more. I think the designers/builders/state QC inspectors are still at the finger-pointing stage with no resolution in sight.

I hope your Nipigon Bridge repairs don't go as badly as this!