Partial bridge collapse during demo

[huntley101888]

http://www.kcci.com/r/27659704/detail.html

Did any of you guys see this story out of Iowa? It looks like they removed the center span out of the continuous three-span beams and then drove an excavator on what was left. Those beams weren't designed for that loading scenario, so it's no surprise that they failed.

On a side note, I wish news outlets would research the correct terms to use in their stories. Pier. It's called a pier.

 

[huntley101888]

I forgot to mention (for those who don't have time to read the article or watch the video right now) that no one was injured in this incident.

 

[csd72]

Why do they never ask the opinion of a qualified structural engineer?

A MOT construction supervisor! If he knew the reason it collapsed then he would have prevented it happening in the first place.

This is the type of lack of understanding that keeps me employed as a temporary works engineer.

 

[DWHA]

This is why in Illinois the state requries demo plans to be signed by an SE. I think all states should do the same.

 

[Spartan5]

I forgot to mention (for those who don't have time to read the article or watch the video right now) that no one was injured in this incident.

The article states otherwise:

Two people standing on the deck were hurt when it collapsed. The workers are employed by Minnowa Construction Inc., of Harmony, Minn. Project Manager Ben Thorson said one worker suffered a cut on his forehead. The other suffered an injured wrist. They were taken to a local hospital for treatment.

They weren't seriously injured. Which is very fortunate.

 

[huntley101888]

Yep, you're right Spartan. I forgot to add "seriously" to my post.

We have a bridge replacement project going on right now in Greene County, NY where the contractor gave us a lot of crap because we demanded more information and calculations in their demo plan before it could be approved. He didn't want to provide the additional calcs, so he instead altered his demo plan until we were comfortable with it.

 

[hawkaz]

One reason reporters never talk to engineers is because we won't give off-the-cuff answers. We want facts, and that takes time. They won't wait for the correct information, they need to run with whatever they can get.

 

[JAE]

That looked strange to me - the girders appear to have a flexural failure at midspan- a brittle break type failure and the ends of the girders don't show any extended top reinforcement or tendons.

Flexural failures are usually more ductile than brittle. At least they are supposed to be.

 

[SteelPE]

JAE

It almost looks like a clean break. That seems very strange to me. It almost looks similar to construction would would find in a cantilever beam system.

 

[MikeHalloran]

Around 1:13 in that video, we see the stub ends of the center span.
There are some odd axial splits near the top, and the entire bottom seems to have spalled off, as if the rebars were pulled out of it axially. We see short bits of rebar protruding, too.

At 1:34-ish, we see a close-up of the midpspan fracture, with an object near the foreground that at first looked like a rebar, but on closer examination looks more like a rack. I have no idea what that would be doing there.

At 1:54, we see the excavator, having miraculously gotten off the rubble without damage, apply a jackhammer to the standing partial span, which seems to crumble immediately, as if unreinforced.

Of course, much valuable forensic material is now gone...



Mike Halloran
Pembroke Pines, FL, USA

 

[JStephen]

Similar incident at a demolition project in Galveston (I think this hotel was damaged in the last hurricane and was being demolished due to that):

http://galvestondailynews.com/story/227678/

 

[JStephen]

And probably a stupid question, but are bridge beams like that ever post-tensioned?