Ontario Cable Stay Bridge Failure

[Brad805]

Some engineers in Spain are going to have an interesting few days of review/discussion ahead of them. 2' of movement seems to suggest something was fundamental was missed. It is posted in the failure section too, but it would be interesting to hear some comments from people that design cable stay bridges.

Link to news story:

http://www.cbc.ca/news/canada/thunder-bay/nipigon-river-bridge-closed-transcanada-1.3397831

 

[rb1957]

the tension cables are (looks like symmetric) and the difference in spans in a short "overhang" span.



another day in paradise, or is paradise one day closer ?

 

[azcats]

Also not a bridge guy -

So when they're building one of these bridges - do they have to calibrate the installation stress in the cables to the temperature during installation? The forces induced with the temperature there must be massive.

 

[gwynn]

Littleinch

It is unlikely that the root cause was the opening of the bridge with only two lanes. This is standard procedure (at least in Canada) for replacing bridges which are critical links. This is not a new situation for the design firm.

 

[LittleInch]

I can appreciate it often happens to part open a bridge, but I always wonder if the same level of design analysis went into the "temporary" design compared to the "final" design.

It does look though like the holding down system / bolts / structure has failed, but the uneven nature of the pull up may have something to do with only half of the bridge being built?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[oldestguy]

Let's get a detail of the hold down system before speculating. To say temperature contraction was not in the design also is speculating and likely a false presumption. Bridges are always built to allow for temperature changes of dimensions.

 

[IRstuff]

" Bridges are always built to allow for temperature changes of dimensions."

The pictures shown already demonstrate that; the bridge is split on an expansion joint.

TTFN
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[rb1957]

following the partial assembly storyline ... the 1/2 bridge, 1 road deck supported by 2 towers, is possibly better than the full design, 2 decks with 3 towers. By eye the 3 towers and cable systems look alike, and the middle tower should have something like double the load on it ... maybe a tower has the capacity to carry the load from 1 deck (ie 2 1/2 decks and make all the same as the highest loaded one) or a minimum of 2/3rds of a deck (ie 3 towers, 2 decks).

another day in paradise, or is paradise one day closer ?

 

[chicopee]

An unlikely scenario is frost heaving of the pier footing. A good case for not contracting Spanish engineers/Design firms. Only contract/hire those experienced in very cold weather.

 

[rb1957]

my 2c ... the cables contracted with the cold and overloaded the fasteners (rivets?) on the deck vertical face, between the cable stayed span and the short cantilever, in shear.

another day in paradise, or is paradise one day closer ?

 

[oldestguy]

For the discussors here take a look at various references and papers that come up when you search for "Cable stay bridge design". Looking at all the details and inputs to consider, the attorneys will surely have a great time with this one. While cost per foot of span may be cheapest, this one bridge probably will make changing that opinion an obvious one for future bridges.

 

[Brad805]

You can see the makings of a significant tie down in the picture below. There are massive anchors protruding into what appears to be the start of a huge cap to deal with the uplift forces bridge buster alluded to. I bet the bolts that failed were the one between the steel girder that would have extended to the caps.

 

[rb1957]

these ones ? between the rigid ground support and the span supported by the contracting cables ...

another day in paradise, or is paradise one day closer ?

 

[TLHS]

We're all guessing, but thermal contraction in combination with other factors is what pops out to me as well.

I'm wondering if someone forgot to check the half built case in the cold and distributed the thermal effects from the centre set of cables into both bridge decks and their anchorage instead of just one. Then it's winter time with only one deck built and suddenly the centre cables aren't facing the resistance that was expected. From the short term fix, it seems like it just needed a bit more weight to get it back to the right elevation, so the .

I can very much see a situation where someone goes "It's extra strong when there's only one deck there" so only does a surface level check of things and then misses the strange case where it's not.

Or maybe the whole thing was designed just fine and there was a construction problem, or some sort of crazy unexpected load action.

 

[gwynn]

Just to head off any further comments about Spanish design firms not knowing cold weather - I beleive the firm is a conglomerate that owns many other firms. The two firms that took part in design of the bridge are both Canadian. Here is the Canadian Consulting Engineer article on the start of the bridge construction:

http://www.canadianconsultingengine...ge-in-ontario-starts-construction/1002543761/

The engineering design for the bridge is by McCormick Rankin Corporation of Mississauga, in conjunction with Buckland & Taylor of Vancouver, who have designed cable-stayed bridges around the world.

 

[Brad805]

@gwynn: Yes, I was told that there was a design firm involved before I noticed that the lead team was North American. My error.

 

[oldestguy]

From what I can find, this firm was involved with overall responsibility. Note the area of their projects seems a little far away. Note the MBE status.

HOWEVER WITH THIS EDIT NEXT POST CORRECTS ME. THANKS

http://www.iegroup.net/about.html

 

[gwynn]

@Brad805
No worries. The news has been plastered with comments about a Spanish firm designing a Canadian bridge, so I am sure a lot of people thought that was the case.

@oldestguy

You have the wrong Infinity Engineering. My understanding is that they were doing the construction engineering, not the bridge design.

http://www.infinity-engineers.com/

http://www.infinity-engineers.com/infinityprojects/nipigon_river_bridge.html

 

[oldestguy]

TLHS probably hit on something about this partial build situation. Note the apparent diameter of the cables on the south side. Twice the size of the north side?