Part of I-85 collapses in Atlanta after massive fire

a reply to: Vasa Croe

Thanks, I did read about the 404 and the Rednecks explanation. I still think something fishy is going on as someone else said it would take some fire to ignite the PVC

a reply to: TheRedneck

Thanks...I've finally caught up with all posts

I'm leaning toward intentional, here's why.


1) To achieve this kind of heat for concrete and steel to fail it takes intense heat, so how much is intense?

2 ) Steel or support steel typically must retain all it's strength at 800 degrees.

3) Concrete depending on the aggregates used can have a failure temp of around 1200 degrees.

The fact that this structure has columns concerns me because when a structure has support columns, it should hold up for a much longer time under heat.

In conclusion, it took some intense heat to make that bridge fail, as the heat that had to be over 1200 degrees for a prolonged time to make it fall.

The question we should, or the authorities should be asking is what accelerant was used to achieve a structure that was meant to withstand extremely heavy loads over many years.


Here's a good general guide for steel and concrete FYI

www.cement.org/docs/default-source/th-buildings.../fire-concrete-struc-sei-08.pdf



I'm also not buying the PVC burning story, because the top temp for burning PVC does not exceed 560 degrees.

a reply to: Realtruth

I tend to agree with your numbers. I wanted to add in another variable, though. If any of the steel was exposed to the fire, the heat from the fire would use the steel like a conduit. That would place the high temperatures more throughout the concrete than on the surface, and cause it to fail much faster. Theoretical fireproofing assumes no exposed metal, and relies to an appreciable degree on concrete's inherent thermal insulating properties.

Just a piece of exposed rebar would cause this, although the more exposure the faster it would cause failure.

TheRedneck

a reply to: TheRedneck

Given the ruinous state of many overpasses, bridges, and other elements of the US transport infrastructure, many of which have been broadly discussed in the media and indeed this very site, it is entirely likely that the metal underframe of the structure was, in places, exposed directly to the heat.

a reply to: Vasa Croe

LMAO! That's about right. Now we just need a low-riding ghetto version of that and another of a Porche or Mercedes, just to complete the stereotyping trifecta of our indigenous peoples.

a reply to: TheRedneck


I'm not totally negating the pvc idea, but they would have had to pile that stuff up the full length of the bridge, bottom to top to make me even start to believe.

I guess if the concrete and steel were substandard grades it may fail around the 500 mark, but I'll be damned if I'm going to believe there was enough fuel to reach that temp, for a prolonged collapse time.

I hope they take samples and publish results, or I hope some independent people get some debris.

a reply to: TheRedneck

According to a national survey/investigation of infrastructure this bridge was considered "critical but not structurally deficient" whatever that means.

a reply to: Realtruth

With regard to the top burning temperature of PVC, was this upper limit established in a controlled environment, with a low to zero draft?

The only reason I ask, is that if wind is traveling through a hollow structure, it creates vortices within them. Once alight, air is also SUCKED, as well as being blown, into the hollow structure, resulting in a much faster burn, and increased temperatures.

a reply to: TheRedneck

There is speculation that it was a fire in an electrical box that feeds the interstate cameras. Just speculation from pics though. You can see it some of the links previously posted. Fire definitely started at the outer edge of the elevated highway, the area beneath was being used as storage by Georgia Department of Transportation. The giant spools of cable filled in a fairly large fenced area. A pic I saw last night appeared to show some drums/cannisters but no one has accounted for what may have been in there. And now I can't find that pic as all the previous links have morphed now as the story developed. Here are some others though:


imgur.com...
imgur.com...
imgur.com...
pbs.twimg.com...

originally posted by: TrueBrit
a reply to: Realtruth

With regard to the top burning temperature of PVC, was this upper limit established in a controlled environment, with a low to zero draft?

The only reason I ask, is that if wind is traveling through a hollow structure, it creates vortices within them. Once alight, air is also SUCKED, as well as being blown, into the hollow structure, resulting in a much faster burn, and increased temperatures.

Yea that would explain the extra intensity, if there was an air induction and perfect fuel to air ratio, similar to an oxygen acetylene torch.

I would buy that theory 100%.

Temps between 3500 and 6500 degrees would make that thing fall within an hour or so, in fact, at those temps the steel and concrete would actually burn itself.

Gentlemen, some of you are already coming down with Dealy Plaza Syndrome.
Forget about it and look further down the road.

On a side note, prior to last year, the last time the Cubs won the Series, it was in back to back years.
1907 & 1908.

Buck

a reply to: flatbush71

Unless there is a syndrome which creates a non-zero chance of having a rifle round blasted through ones head, in an open topped car, I think I am missing your meaning there.

a reply to: Realtruth

I'm not thoroughly convinced it was a CPVC fire... I'm thus far just going on reports, trying to verify the official explanations. I'm not intimately familiar with that specific area; most of my experience in Atlanta comes from driving semis, and they don't allow big trucks inside the I-285 loop except for pickup and delivery. My hope is that maybe by analyzing it in this sort of stream-of-consciousness I use, someone intimately familiar with that exchange will have an "aha!" moment.

I know different states use different standards on construction materials. What is just fine and dandy in Georgia will get a contract revoked in Florida. Georgia will reject materials that are perfectly acceptable in other states. And of course there is the ever-present corruption ghoul lurking around... did someone grease enough palms way back when to get to cut some corners on the contract?

Incidentally, concrete failure starts much colder than those temps you mention, but it is so slow it is considered irrelevant. That's why concrete crumbles with age... it's actually crumbling from temperature, but it takes decades to show up at all. As the temperatures increase, the speed of the crumbling increases drastically. At rated temperatures, if you dig you'll find there's a time consideration as well: "800 F for 15 mins. with a maximum total degradion of 1%," or something along those lines (I just grabbed the numbers out of thin air for example purposes only).

TheRedneck

a reply to: mikell

I don't know if I'd with "better".

Scarier?

As a native Atlantean (born and raised), my thoughts go out to any of y'all that this will affect in terms of travel. My mom moved up to Cumming about 10 years ago, so I catch 400 right there when I visit. Guess I'll have to take 285 (shudder).....or maybe just not visit for a while!!! Haha!

I really feel for the commuters.....

a reply to: kosmicjack

OK, that was helpful!

The condition was probably related to the collapse. I have no doubts on that. But those pics... thank you!

IMO, as an engineer (and pyromaniac hobbyist ), the pictures do not show nearly enough plastic to cause a catastrophic failure. They do appear to be sufficient to produce the volume of smoke, but not the temperatures; they are too far separated and too far from the actual structure. Those drums on the other hand... what was in them? They are easily close enough to the conduit to have ignited it, producing the smoke indirectly, and producing the needed heat directly. That would easily explain the instances of flames I mentioned earlier... it was drums igniting. It makes sense that the drums stored near the initial ignition source would ignite rapidly after the initial start (initial explosion and primary heat source), and those farther from the ignition source would ignite more sporadically as the fire continued (sudden bursts of flames amid the smoke).

Can anyone shed some light on that? Liquid, normally stored in 55-gal. drums, next to electrical conduit, highly flammable, used by the DOT?

This is starting to not look like just some burning conduit...

TheRedneck

originally posted by: Gryphon66

originally posted by: 3NL1GHT3N3D1
a reply to: Gryphon66

I've lived here my entire life and racism has never really been prevalent at all in my experiences.

You can't judge an entire state by a minority of racists, that's ridiculous.

Well, I'll admit, I'm usually razzing on my conservative fellow Georgians, but as you say, most of them are good people. This is a major catastrophe that's going to cause real problems for weeks and maybe months. I can't believe anyone would basically say we deserve it based on Wikipedia.

I was going to say, you've talked quite differently in past threads about your area.

OT- Ironically, I was just reading a thread on reddit a day or two ago about how absolutely horrible the traffic is in ATL. I'm sure this just added hours to people's commutes.

a reply to: TheRedneck

I can't find the pic that clearly shows the drums. The pics posted above all show stacked conduit. I think. But last night I saw a pic of drums - or so I thought - from a twitter feed. Was it the stacked conduit just giving the illusion of drums?

Here is a pic of the collapse:

i.imgur.com...