knight1fox3

I-85 fire: Section of Atlanta highway collapses

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Aren't highways in the US mostly concrete?  How does that burn?

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Hmm, steel structure collapsed from only a fire load.....

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the one good thing about a fire is that they will be able to trace what started it within a few days. My ATL friends are already pointing to some conspiracy theory about some old rolls of conduit stored under the bridge from a project that went south a few years ago as the "fuel".. But I would think you would need some major accelerate (gasoline, etc) to get a bridge to burn.. but yes anything can burn..

Traffic is going to be so fucked....

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This is the image that is being circulated that is prompting the "rolls of conduit" theory.  The conduit wouldn't just spontaneously combust so there had to be something else that sparked the fire.  My guess would be urban outdoors-men...

GDOT stores a lot of crap under this bridge.  I know they park HERO (Highway Emergency Response Vehicles) under another portion of the bridge.  When the fire was initially reported I assumed it was those burning.  I'm betting there will be a new directive from GDOT soon dictating that nothing should be stored or placed under bridges.  

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that (storage) probably happens all around the country though.

So is that photo from before the fire "went crazy"?  I am not fire expert but it just doesn't seem to me that there is enough plastic there to generate enough heart to burn a concrete bridge?

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Posted (edited)

38 minutes ago, Road Guy said:

that (storage) probably happens all around the country though.

So is that photo from before the fire "went crazy"?  I am not fire expert but it just doesn't seem to me that there is enough plastic there to generate enough heart to burn a concrete bridge?

It all depends on how long the fire continued to grow. In it's "growth" stage, a fire doubles in size every 30 seconds. If it's inaccessible, then that would only add to the delay in supressing it

Edited by NJmike PE

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another thing to consider is what was in those "storage" containers. They clearly were not empty and I doubt it was plastic alone that generated that heat. Whatever the accelerant was, it burned hot enough and long enough to weaken the steel connections.

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I don't do road design, so I'm not sure about the typical assembly, but it looks to me like the fire melted the expansion joints causing the rebar to become exposed, the rebar then weakened and the whole section collapsed under its own weight. I don't think there's any other way to get such clean break lines on both sides of the collapsed span without it being an expansion joint failure.

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its just rolls of conduit, no containers that I could see (google street view)

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the bridge beams usually sit on the bridge "cap" (abutment) usually there is a foot or so of the concrete beam that rests on the cap, which supports the load. It would have had to burn hot enough to melt that overhand enough to allow it all to break clean.. from the pics I saw on news it looks like the "caps" are still intact somewhat

not sure how old this google street view pic is but there is a lot of conduit, maybe that would be enough. but you have to think it would have taken some serious flame to get that going..

 

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The report should be interesting. Definitely going to be some finger pointing involved

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Did RG design that road?

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1 hour ago, Road Guy said:

the bridge beams usually sit on the bridge "cap" (abutment) usually there is a foot or so of the concrete beam that rests on the cap, which supports the load. It would have had to burn hot enough to melt that overhand enough to allow it all to break clean.. from the pics I saw on news it looks like the "caps" are still intact somewhat

not sure how old this google street view pic is but there is a lot of conduit, maybe that would be enough. but you have to think it would have taken some serious flame to get that going..

 

AAAAAAAAAA.png

Holy cow! That street view pic is from November! I doubt they had moved any of that material since then (assuming that's the portion that collapsed). I didn't realize conduit could burn that hot. Guess I learn something new every day.

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43 minutes ago, Ship Wreck PE said:

Did RG design that road?

lol - I did some design on I-85 further north and way further south back in the day, but that's not my viaduct!

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this pic shows the cap is still mostly "there"  check out the column (can barely see at the bottom) looks like another section of the bridge each side will also have to go.

bridge.jpg

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damn, so the girders failed..... all together?

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I'm glad they are tied off and wearing hard hats. 

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Safety first. Always.

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those look like surveyors who are not smart enough to listen

I think this will work until they get it fixed - just change direction for AM / PM Rush Hour

hotwheels.jpg

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I'm glad they are tied off and wearing hard hats. 

Shhh OHSA doesn't need to know.

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Hard hats?  In case things fall from the sky?  Tied off is probably not a bad idea, though

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18 minutes ago, MA_PE said:

Hard hats?  In case things fall from the sky?  Tied off is probably not a bad idea, though

Our agency is a hard hats on in the field, all the time, no questions asked. It stems from an OSHA fine a few years back. 

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Hard hats always on the jobsite. I know it looks silly in this case but we had a few of our go home alive because they were wearing hats. You don't want to deal with a complaint to OSHA.

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Should be ready by Monday. f3d1a75563b017a0e072e7164c49a403.jpg

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