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Fire in Atlanta

Fire in Atlanta

Fire in Atlanta

From the AP, " A large fire has caused an overpass on Interstate 85 to collapse in Atlanta.

WSB-TV reports the massive blaze is burning underneath I-85 northbound near Piedmont Road. It has shut down several roads in northeast Atlanta.

Witnesses say troopers were telling cars to turn around on the bridge because they were concerned about its integrity. Minutes later, the bridge collapsed."


RE: Fire in Atlanta

This is not an engineering failure, since fire proofing bridges is not normally required for their integrity. Also that may fail if damaged by the vehicle underneath. World Trade Center disaster was due to fire proofing failure by damage from plane.

RE: Fire in Atlanta

Whether it is an engineering failure or not, I85 is closed, probably for a long time. Big problem.

RE: Fire in Atlanta

Apparently there was a fenced in compound under the bridge at that point, containing spools of what appears to be Polyethylene gas pipe. A large quantity.

You are judged not by what you know, but by what you can do.

RE: Fire in Atlanta

I am pretty confident it was underground fiber-optic conduit on spools (not sure if it was just bare conduit). I also think it was GDOT's yard.

Robert Hale, PE

RE: Fire in Atlanta

It's so enticing to store stuff under these massive weatherproof concrete umbrellas but what an expensive disaster when any of it burns. Makes me think of good old fire-happy Oakland where for miles the elevated freeway is over shanty-towns, auto-wrecking yards, industrial equipment piles, warehouses, garages, bus storage, abandoned buildings, etc., etc.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Fire in Atlanta

Good thing that Oakland doesn't have fires...

RE: Fire in Atlanta

Can't find much on the internet about it, but in 1986, a gasoline tanker was involved in a collision and caught fire on Ontario Highway 401 directly underneath the James Snow Parkway bridge (exit 324). A temporary detour for the highway was constructed very quickly - if I remember right, within a week. But, this happened long before significant commercial development all around that area, and it would be a much bigger challenge to do the same today, and certainly a huge challenge to do this in Atlanta.

RE: Fire in Atlanta

I found a few quotes interesting on this:

Experts in structural engineering said fires on highways and bridges rarely burn long enough or hot enough to cause a complete collapse — but it has happened. Intense heat can compromise even steel-reinforced concrete, said Lauren Stewart, director of the Structural Engineering and Materials Laboratory at Georgia Tech in Atlanta.
It is SO nice to have a reference to "structural engineering" instead of "An Architect stated...."

McMurry said his department stored coils of plastic conduit, used in fiber optic networks, beneath the span but insisted they were noncombustible.
So if these coils were non-combustible, what the heck fueled such a hot fire?

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RE: Fire in Atlanta

Looking at the photos and if I was a homeless guy (we used to call them tramps) that site looks mighty appealing for a hang out. Nice roof too. Move a few piles and set up your camp. Maybe start a small camp fire for warmth or heating that coffee you scrounged from down the road. Gosh, I didn't know that stuff would burn.

RE: Fire in Atlanta

"Non-combustible" or "self-extinguishing" might be true if you try to burn an individual piece of that plastic, but an entire mass of it can be a different story. The Mont Blanc tunnel fire disaster in 1999 involved a truck carrying margarine, which one wouldn't normally think of as a hazardous material, but it contains more or less the same energy content as oil.

RE: Fire in Atlanta

The sound you hear is highway departments from coast to coast making sure they don't stage any HDPE under their bridges.
So the next fire will be of something slightly different. Like PE pipe

RE: Fire in Atlanta

I wonder if the cables were lubricated for ease of pulling. Wouldn't surprise me if that was what burned and was hot enough to sustain all the other combustibles plastics in the area. I'd also think coils of tube would make great chimneys to direct fire upward.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

RE: Fire in Atlanta

Can't see much in that area but speculating here: don't forget the wood spools, wood pallets, and who knows what other material; cardboard boxes, tarps, etc. likely in the area.

RE: Fire in Atlanta

What could have been the source of the heavy black smoke prior to the collapse?

"Where the spirit does not work with the hand, there is no art." - Leonardo da Vinci

RE: Fire in Atlanta

Plastic heated to its melting / decomposition temperature is just like any other hydrocarbon, and when burning in a situation where heat is in ample supply and oxygen is in short supply, it's gonna be a black smoker.

RE: Fire in Atlanta

By the time it got to that stage it would be running and forming pools of burning liquid on the ground. Burning like a World War II naval battle.

RE: Fire in Atlanta

"Non-combustible" or "self-extinguishing" might be true if you try to burn an individual piece of that plastic, but an entire mass of it can be a different story.

Agree. The "self-extinguishing" material rating is misunderstood by many and would appear so in this case in the decision to store probably what was UL-94 rated plastic material under the bridge.

The problematic part of that rating is that the self extinguishing test is in part a heat transfer issue.. A single specified piece of material suspended per the test may well receive the rating, but that same material in a confined area, with reflected heat, other ongoing ignition source, or otherwise different heat transfer/escape characteristics means it may burn rather violently.

Learned this in an evaluation of an issue in a fairly large digital system using an extensive amount of ABS UL94 rated plastics. The plastics first melt into a black tar like residue (plastics being a petroleum derivative) and then ignites and burns with the ferocity of a petroleum fire. The materials engineer in this investigation mentioned that the bromine and other compounds added to plastics for the flame retardant rating yields considerable chlorine gas when burned.

RE: Fire in Atlanta

The byproduct of burning halogenated plastics or those containg halogen fire retardants is hydrogen chloride (or hydrogen bromide, which will combine with moisture in the air or lungs to form hydrochloric acid). At high temperature, plastics will burn like gasoline and fire retardants will have a negligible effect, except for making the smoke more toxic.

RE: Fire in Atlanta

That'll enforce the minimum speed limit!

RE: Fire in Atlanta

Depends on how high the loop. <G> It was off topic, but, thought it was cute.


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