Truss Bridge Collapse 3

[CANPRO]

This just happened yesterday in rural Nova Scotia. The bridge was scheduled for replacement. Collapse took place while the contractor was moving equipment in to start the work. One worker in hospital (assuming the truck driver).

I of course don't want to see anyone get hurt, but I find these failures fascinating. The video and sound quality isn't great, but it sounds like there was indication the bridge was failing. The worker walking on foot on the far right seems to get off the span quickly just before the collapse. We will need to get more info, but my initial speculation is that one of web members failed.

https://www.cbc.ca/news/canada/nova-scotia/bridge-collapse-guysborough-county-worker-1.5641319

 

[LittleInch]

Looks to be a form of a pratt truss bridge, but looking at the GE streetview, I'm not sure I would want to drive what looks like a v heavy load accross such a bridge.

Those struts look very small to me. Picture is the bay which looks like it failed.

No posted weight restriction. NO other vehicle access to this little Island.

Paste this into GE maps for location 45.339964, -61.015677

https://goo.gl/maps/tPygYeFuohczTLK47

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

 

[saikee119]

Only Google Street View allows us to take a look and pass a bridge already collapse. In this case we can even view 360 degree at the spot where the collapse happened.

The wonder of techology.

 

[bimr]

The picture doesn't completely show what is on the truck trailer, but it looks like a 50 ton tracked excavator.

It looks like the bridge falls as soon as the rear wheels roll onto the bridge.

What are these workers thinking?

 

[LittleInch]

Indeed. I took one look at the truss cross connections and thought I wouldn't have allowed the EMPTY truck and trailer across it, never mind with a large machine on the back.

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

 

[Sym P. le]

What are these workers thinking?

"This is an epic move. I better get a video!"

... the first indication of trouble afoot.

 

[waross]

Video
The tri-drive truck pulling a tridem trailer is probably over the weight limit empty.
The machine may have been over twice the weight limit by itself.

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

 

[CANPRO]

The CBC article I linked in the first post has been updated stating the weight limit on the bridge was 41,500 kg. The video posted by waross appears to be the same video in the CBC article put clearer - looks like a man-lift to me.

 

[Sym P. le]

From the video linked to by waross, the equipment appears to be a track driven crane. If it was equipment to be used by the contractor to replace the structure, they should be well qualified to determine for themselves that the bridge could handle the load. Maybe next time ...

 

[LittleInch]

Looks like a hefty bit of equipment to me.

And as for 41 tonnes weight limit??? Get away. More like 15 or 20.

Love to know what replacement brdige they're going to get in 48 hours... It will take that long to get the old one out of the way with a truck wedged in it.

On the second bay on the right as you look at it the strut is missing.

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

 

[EdStainless]

Maybe it was 41k pounds and they forgot to convert and just changed units.
Too bad he didn't back up when it started to deform. At least they would be able to use it for foot traffic.
Maybe they were going to be forced to dismantle it and they wanted to rush the demolition phase .....

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[waross]

Love to know what replacement brdige they're going to get in 48 hours

This may be ruled out if there are strong tidal currents, but I would consider some culverts and fill.
It doesn't have to be level.

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

 

[hokie66]

I hope the truck driver wasn't injured. But any competent engineer could have advised them not to use the bridge for that purpose.

 

[3DDave]

Army Corp of engineers would have a bridge in place already.

I doubt there was much warning - Euler buckling means that there is little deflection and then BOOOM! Like increasing the load when crushing a soda can the long ways. Or it could be a failed fitting on a tension member. Either way there's little difference between a bit of deflection and failure.

 

[3DDave]

hokie66, At least it wasn't Swift this time.

 

[JohnRBaker]

Yea, just throw-up a Bailey Brdige:

https://www.youtube.com/watch?v=aOrGv8S5yjE

And if you have enough manpower, you could do it without that 'yard crane', although 48 hours might be a bit fast. More like 72, I would expect.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
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UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[hokie66]

3DDave,
Trying to figure out what "Swift" means, but maybe I missed something.

 

[saikee119]

My jaw will drop if the bridge can only take 41k lb as that will be about 18 tons.

If we expect the bridge to pass a laden ready mix truck then the bridge has to be good for at least 32 tons.

CBC news reported

A spokesperson for the Department of Transportation and Infrastructure Renewal said the bridge was last inspected in April, and it has a maximum permissible weight of 41,500 kilograms.
Vernon Pitts, the warden of the Municipality of the District of Guysborough, said he believes the truck and its load would have been over the bridge's weight limit.

 

[3DDave]

Swift carries a, uh, reputation.

https://www.google.com/search?sa=X&...qAhV1dc0KHf1FC34QsAR6BAgKEAE&biw=1280&bih=678

 

[saikee119]

Assuming the bridge has been certified to take 41 tonnes (metric tonne is nearly same as Imperial ton) can we establish the load was over the bridge limit by the fact that the transportor had not yet reached the mid span where it would cause the maximum stress/shear/moment to the bridge? The bridge has 6 rectangular bays and the transporteris seen to occupied only the first 4 bays when it collapse. I am sort of gathering a common consensus on the root cause of it assuming the Department of Transportation's last inspection in April holds water for the maximum permissible weight of 41.5 tonnes.

I am a bit puzzled by the fact that the bridge has a narrow warning sign at the north side where the transporter approached.

Thus someone must have checked the width of the bridge at least to make sure the transporter can pass through and the bends are suitable. The fact that workmen had to be deployed to guide the transporter through would suggest the operation must have been planed, surveyed, route checked and bridge capacity verified.