Canadians stranded after bridge splits amid intense cold 3

[waross]

Canadians stranded after bridge splits amid intense cold

http://www.theweathernetwork.com/ne...ts-brand-new-bridge-strands-canadians-/62165/

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[cranky108]

I believe there is a railroad that crosses Canada. So to say this splits Canada is not exactly true.

It also read they don't know what happened. So much for media getting the story.

 

[jayrod12]

One of the witnesses said it was right in the middle of a high wind event.

Speculating here, but is it possible the slide bearing didn't have any uplift resistance?

 

[JohnRBaker]

This is indeed a new bridge of a style, cable-stayed, that has become popular over the last 30 years or so.

In 1985, Professor Henry Petroski published a book titled, "To Engineer is Human: The Role of Failure in Successful Design" (which I highly recommend) where he talked about, among other things, why it is that there has always been, and will continue to be, bridge failures particularly when a new style has started to gain popularity, but generally only one example of a failure will occur. This is because (to paraphrase the good professor) "When it comes to designing a new style bridge, since virtually all bridges are paid for with taxpayer money, in order to reduce costs, safety factors for these new and radical designs will be reduced until there's a failure, at which point the engineers will go back to the last example that did not fail and it will thus become the minimal standard going forward."

In fact, at the end of the chapter covering bridge failures in the above mentioned book (the cover of which shows a bridge failing, the infamous Tacoma Narrows Bridge), Petroski predicted that with respect to the newly introduced 'cable-stayed' designs, that is was just a matter of time before we would see at least one significant failure of this type of bridge.

Now I'm not sure that we could call this Canadian incident a "significant failure", but in terms of the potential impact on the traffic, both commercial and private, on the Trans Canada Highway, to say nothing of the impact on US 28, the primary East/West (and almost all two-lane) highway across the UP (Upper Peninsula) of Michigan, which was mentioned in the news item as being the only practical alternative route, this could be a long remembered failure. And with this being winter, anyone familiar with the UP (I lived there for six years) knows that with lake-effect snow coming off of Lake Superior, that the Trans Canada Highway, despite being further North, is a much less treacherous route this time of year (see image below where green shows approximately where the Trans Canada Highway runs versus the red which is basically the route US 28, shown during what is called a 'lake effect' snow storm):

Some interesting links:

https://en.wikipedia.org/wiki/Henry_Petroski

http://www.amazon.com/gp/product/06...mp=1789&creative=9325&creativeASIN=0679734163

John R. Baker, P.E.
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[oldestguy]

Some discussion in the other thread indicates temperature shortening of the cables. A look at the temperature records for the last year or so might tell something. Here in Wisconsin we are having our first very cold days of winter and we are not far from that bridge.

 

[allgoodnamestaken]

"When it comes to designing a new style bridge, since virtually all bridges are paid for with taxpayer money, in order to reduce costs, safety factors for these new and radical designs will be reduced until there's a failure, at which point the engineers will go back to the last example that did not fail and it will thus become the minimal standard going forward."

 

[IRstuff]

The pictures show a vertical displacement in the roadway.

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faq731-376 forum1529

 

[oldestguy]

The temporary fix would be of interest here.

http://www.chroniclejournal.com/new...cle_127f422d-3b88-504d-a31a-d0abedc9c97e.html

I also found this:

Harvey said the bridge has only been open for about two months ago and was the largest most expensive bridge project ever undertaken in Ontario.

 

[JohnRBaker]

With the roadbed heaving/separating by nearly 24 inches (60 centimeters) on a bridge that has been in service for only 2 months, would you honestly feel safe driving even a private vehicle over whatever sort of makeshift 'patch' that they've managed to lash together in a couple of days in the middle of winter? I know I wouldn't, but then I have acrophobia and besides, I've never learned to swim ;-)

John R. Baker, P.E.
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Digital Factory
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[IRstuff]

Luckily, you don't have to swim; if you fall into the water, the hypothermia will get you before you drown ;-)

TTFN
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[oldestguy]

I did a Google search for temperature effects on these bridges and there is a whale of a lot of info there, mostly recent and from China, etc. Temerature measurements generally show the main girder top and bottom are different and less variable as cables.

Here is a little. It looks like they are in need of a lot more study. Now this is a good time for Canada to instrument this one if it is not already so equipped.

http://shm.sagepub.com/content/10/5/523.short

CONCLUSIONS
Based on the measurements taken on Ai-Lan Bridge from September of 2010 to
date, the modal frequencies of 18 cables and the temperatures of air and different
structural components are analyzed and cross-examined in this paper. The results
clearly indicate that temperature is the major environmental factor to cause the
variation of cable force. A simplified model proposed in this study also demonstrates
its effectiveness in correlating the variation of cable force with an effective temperature
variation simultaneously considering the temperature effects from the pylon, girder,
and cable. With this progress, a structural health monitoring methodology mainly based
on the identified cable frequency from measurements will be further explored and
applied to Ai-Lan Bridge in the near future

 

[JohnRBaker]

In that picture, posted earlier in this thread, looking down the length the bridge, it almost seems like the roadbed is bowed upward, which would be the case if the longer cables, being longer, contracted more than the shorter ones. Since, unlike a conventional suspension bridge where any contraction/shortening of the vertical cables would have simply 'raised' the roadbed, in a cable-stayed bridge, the contraction/shortening of the cables would have put the roadbed into both a compressive and a bending moment, raising the ends and perhaps causing them to fracture/separate away from the abutments.

John R. Baker, P.E.
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Product Engineering Software
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To an Engineer, the glass is twice as big as it needs to be.

 

[oldestguy]

John: There is another shot in a newspaper article showing that curve clearly. However, none of this would have happened if the various parts of the bridge were all at the same temp and had the same coef. of temperature dimension change. Some of the info I have reviewed shows for several such bridges equal temps just does not happen. A quick check on concrete (the slab) indicates it is highly variable.

Here is the link showing the curve. Seems like north side is worse, maybe due to being warmer due to more sun exposure on the slab per the photo.

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

 

[JohnRBaker]

The longer cables will contract a greater absolute distance thus creating the upward force on the outer ends of the bridge where it's connected to the abutments.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
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Siemens PLM:
UG/NX Museum:

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[waross]

The new structure is a replacement for the existing two-lane bridge over the Nipigon River. The new bridge is a four-lane, two-span structure with spans of 112.8 meters and 139 meters. - See more at:

http://www.hatchmott.com/projects/nipigon-river-bridge#sthash.8UCobsu4.dpuf

The bridge appears to be asymetrical. Is this correct and could this be a contributing factor?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[racookpe1978]

So, why have the comparable cable-stayed bridges in Europe not pulled up their ends? Not as cold? Or a compensator on the longer end cables? Or the "end point" conditions of the two abutments different here, so the ends didn't move up far as actually needed?

 

[JohnRBaker]

I think you'll find that the 'asymmetry' was the result of there being a pedestrian walkway located outboard of the suspension cables on only ONE side of the roadway (you can see this clearly in the video showing the bridge under construction that was at the bottom of the page linked in the first post of this thread).

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[Ingenuity]

The bridge is asymmetrical longitudinally and is somewhat asymmetrical (albeit minor) sectionally due to the pedestrian lane.

 

[waross]

John

Butch Cassidy: Alright. I'll jump first.

Sundance Kid: No.

Butch Cassidy: Then you jump first.

Sundance Kid: No, I said.

Butch Cassidy: What's the matter with you?

Sundance Kid: I can't swim.

Butch Cassidy: Are you crazy? The fall will probably kill you.

Sundance Kid: Oh, shit...

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

I was asking about the longitudinal asymmetry. The longest cables seem to attach at different spacing and at different angles.
On another note:
Business is probably quite good at Tim Hortons about 2 miles west of the bridge. (Tim Hortons, A Canadian version of Starbucks)

Bill
--------------------
"Why not the best?"
Jimmy Carter