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[sylvan8798]

Suppose you had a hollow core column coated all round in a thick layer of fireproofing. Then further suppose that this hollow core column was filled with nanothermite. If this was ignited would it liquify the steel instantly. Would all the fireproofing melt together- fuse into a kind of glassy residue forming a hollow pipe of sorts ?

No.

 

[tfk]

For the last time: The external observations showed that the fires were still burning and spreading up to the collapse of each tower. NCSTAR 1-5 very clearly lays this out. So do the expanse of flames and smoke. If any argument is to be made, it needs to be against the evidence laid out in NCSTAR 1-5. No other arguments suffice; any arguments that do not address the observations recorded there fail due to lack of acknowledgement of the existent evidence. Anyone who wants to claim otherwise must address the evidence, otherwise their arguments carry zero validity.

EMH,

You're right about the fires. There seems to be no doubt that the fires were continuing to burn.

It's been said before. The tilt was more important than the temperatures.

It was NOT weakening of the columns due to temperature that caused the collapse of the towers. It was creep of the columns due to (principally) stress and (secondarily) temperature.

If it were weakening due to temperature, then a significant number of the columns would have had to get up to 700°C - 800°C simultaneously. It is unlikely that this happened.

This is precisely why many buildings with massive fires do not collapse. They have the same elevated temperatures that the towers had. But they do NOT have the high, abnormal (i.e., bending) stress levels that they towers had as a direct result of the physical damage from the plane impacts. So those surviving buildings don't have the creep.

In the WTC towers, the physical damage led to high, abnormal stress levels. At those elevated stress levels, even SMALL increases in temperatures are sufficient to cause the steel to creep, and the tower to tilt some more.

The more the tower tilts, the higher the stresses become, requiring even lower temperatures for the creep to continue.

Creep killed the towers.

The creep ultimately led to mechanical failures, such as loss of trusses, loss of lateral supports & buckling, etc.

Quoting from BLGB, "What Did and Did not Cause Collapse of WTC Twin Towers in New York" ...

... the stress in some surviving columns most likely exceeded 88% of their cold strength σ0 . In that case, any steel temperature ≥ 150° C sufficed to trigger the viscoplastic buckling of columns (Bazant and Le 2008). This conclusion is further supported by simple calculations showing that if, for instance, the column load is raised at temperature 250° C from 0.3Pt to 0.9Pt (where Pt = failure load = tangent modulus load), the critical time of creep buckling (Bazant and Cedolin 2003, chapters 8 and 9) gets shortened from 2400 hours to 1 hour


Therefore, to decide whether the gravity-driven progressive collapse is the correct explanation, the temperature level alone is irrelevant (Bazant and Le 2008). It is meaningless and a waste of time to argue about it without calculating the stresses in columns. For low stress, high temperature is necessary to cause collapse, but for high enough stress, even a modestly elevated temperature will cause it.

Creep is more sensitive to stress levels than it is to temperature. And the stress levels were determined by the amount of tilt of the upper block. The fires could easily have been subsiding and the creep accelerating.

And there is zero doubt that the creep (i.e., the tilt) was accelerating.

Tom

 

[Thunder]

Why do so many firefighters have 70's gay porn mustaches?

its called....a side job.

 

[tfk]

are you for real?

Oh, Tom's for real.

He's just not batting for the team that you think he's batting for...

 

[twinstead]

its called....a side job.

Oh no he di'int!

 

[tfk]

Check your inbox

You'll save yourself a boat-load of cc'ing if you just post the link...

 

[twinstead]

You'll save yourself a boat-load of cc'ing if you just post the link...

Indeed

 

[Alferd_Packer]

I didn't realize at first this was in the Conspiracy topic (where I almost never go), but the thread title interested me.

Not to be disrespectful in what is ultimately a serious (and heated) thread, but...

Why do so many firefighters have 70's gay porn mustaches?


I only noticed it because I just saw a show on Travel Channel where firefighters from New York, Chicago, and Los Angeles all rated some pizzas. Many of them had these big, thick bushwhackers that you'd only otherwise see on VHS tape covers in a very special section of the adult video store.

How do you know what 70's gay porn star 'staches looked like?

 

[ve2vfd]

Looking at this as a physicist, it seems to me that there is no need for fireproofing on steel to have melted for the steel to fail.

Thats besides the fact that most of those "fireproofing" materials are meant to give resistance to heat (resistance folks, NOT fireproofing!) for a certain amount of time if it is intact. Most are NOT very impact resistant.

I've seen the standard fireproofing thats applied to the beams and under steel deck roofs get knocked off in patches by violent impacts like a truck running into a wall, or even once a fork-lift hitting a steel column in a warehouse.

It doesn't take a genius to figure out what will happen to the steel if even a few square feet of this "fireproofing" gets knocked off a support beam exposing it to high temperatures. And like a house of cards, you weaken the wrong support and it all comes down.

It takes a heck of a fire to melt steel, but the temps needed to weaken and bend steel is MUCH lower and easily attainable in a fire... just google pictures of warehouse fires and you'll see thousands of steel support beams twisted like pretzels.

Of course everything I am saying is probably a lie, 'cause face it... you can't trust firefighters! he he he...

Pat

 

[Senenmut]

This seems worryingly like the beginning of a complex question fallacy. Looking at this as a physicist, it seems to me that there is no need for fireproofing on steel to have melted for the steel to fail. Fireproofing on steel works rather like pipe lagging in reverse; it doesn't stop the flow of heat into the steel from its surroundings, just slows it down. That's why fireproofing has a protection time rating. After that time, in the standard conditions of the test, even with the fireproofing still in place and intact, the steel will nevertheless have been heated to its point of failure (said point being defined in a manner specific to the rating test; mileage may vary in real situations).

As for whether fireproofing will actually protect steel up to its rated time in a specific fire, that's been done to death many times here; the rating is for a specific set of standard conditions that may not bear much resemblance to a real-life fire, and detailed modelling or testing would have to be done to predict how a specific assembly would perform in specific conditions. Such modelling and testing formed a significant part of the NIST investigations.

Dave

have any firefighters here ever run into fireproofing that was “melted into a glassy residue?”

what would a firefighters thoughts be if one did run into fireproofing that had “melted into a glassy residue?” (be it blazeshield which contains slag wool or the asbestos containg fireproofing. it looks as though the two have about the same melting point.

 

[Furcifer]

Why do so many firefighters have 70's gay porn mustaches?

I suspect it's because it's the only facial hair that can be worn that doesn't interfere with the use of S.C.B.E. (Self Contained Breathing Equipment)

 

[Telltale Tom]

Thats besides the fact that most of those "fireproofing" materials are meant to give resistance to heat (resistance folks, NOT fireproofing!) for a certain amount of time if it is intact. Most are NOT very impact resistant.

I've seen the standard fireproofing thats applied to the beams and under steel deck roofs get knocked off in patches by violent impacts like a truck running into a wall, or even once a fork-lift hitting a steel column in a warehouse.

It doesn't take a genius to figure out what will happen to the steel if even a few square feet of this "fireproofing" gets knocked off a support beam exposing it to high temperatures. And like a house of cards, you weaken the wrong support and it all comes down.

It takes a heck of a fire to melt steel, but the temps needed to weaken and bend steel is MUCH lower and easily attainable in a fire... just google pictures of warehouse fires and you'll see thousands of steel support beams twisted like pretzels.

Of course everything I am saying is probably a lie, 'cause face it... you can't trust firefighters! he he he...

Pat

I don’t think you understand how heat transfer in steel works. Our scientists at ae9/11truth say that even if the steel had no fire protection then it was so massive that the columns would have absorbed all the heat without failing. It says so in our slide show.

But the floor trusses were made out of bar joists with 5/8” 16mm dia bars. And these bars are small, so any local damage to the fire protection would expose the steel to the fire and any heat would not be able to spread away from the damaged fire protection: the heat would be concentrated. And since every element of a truss is critical to supporting it, then it would be susceptible to failure.

But since everyone knows the columns failed first the failure of the trusses cannot be the cause of failure. So explosives hidden in the fire zone were essential to start the building failure.

 

[BigAl]

have any firefighters here ever run into fireproofing that was “melted into a glassy residue?”

what would a firefighters thoughts be if one did run into fireproofing that had “melted into a glassy residue?” (be it blazeshield which contains slag wool or the asbestos containg fireproofing. it looks as though the two have about the same melting point.

I'm not an expert in fireproofing but I know that the heat shields of Mercury/Gemini/Apollo-generation spacecraft kept the cargo cool by vaporizing during reentry. The process is called ablation and this web page kind of suggests ablation may be at work in some kinds of fireproofing. This makes sense since we know that fireproofing only has to work for it's hour rating.

Who knows what the residue looks like after the ablation capacity is used up.

http://en.wikipedia.org/wiki/Passive_fire_protection

 

[BigAl]

I don’t think you understand how heat transfer in steel works. Our scientists at ae9/11truth say that even if the steel had no fire protection then it was so massive that the columns would have absorbed all the heat without failing. It says so in our slide show.

But the floor trusses were made out of bar joists with 5/8” 16mm dia bars. And these bars are small, so any local damage to the fire protection would expose the steel to the fire and any heat would not be able to spread away from the damaged fire protection: the heat would be concentrated. And since every element of a truss is critical to supporting it, then it would be susceptible to failure.

But since everyone knows the columns failed first the failure of the trusses cannot be the cause of failure. So explosives hidden in the fire zone were essential to start the building failure.

Leap to conclusions much? Make ◊◊◊◊ up much?

A WTC fire in 1974(?) was limited to one floor and was contained by the sprinkler system until FDNY showed up yet the fire did structural damage to the truss system. (Cite on request)

Truss systems in fires kill people, including firemen. Firemen train for these fires. Read this:

http://www.cdc.gov/niosh/docs/2005-132/

(see table D-1 http://www.cdc.gov/niosh/docs/2005-132/#ad )

NIOSH Publication No. 2005-132:
Preventing Injuries and Deaths of Fire Fighters Due to Truss System Failures

All-steel trusses present their own hazards when exposed to fire. The mass and surface area of steel truss components are factors that determine time to failure. A heavy, thick section of steel has greater
resistance to fire than a lightweight section of the same length because of the increased mass. A large, solid steel truss can absorb heat and take longer to reach its failure temperature, whereas a lightweight steel truss such as an open-web bar joist will be heated
to its failure temperature much faster.

Once the failure temperature is reached, heavy steel trusses and lightweight metal trusses will react to the fire and fail in a similar manner. A steel member fails at the internal temperature of the steel and not at the ambient air temperature. This temperature is often
referred to as the critical temperature of the steel member.

Findings reported by the National Engineered Lightweight Construction Fire Research Project indicate that unprotected lightweight steel C-joists fail within 4 to 6 minutes of exposure to fire [Grundahl 1992]. Testing conducted by the U.S. Bureau of Standards (now known as the National Institute of Standards and Technology, or NIST) showed that unprotected steel open-web bar joists reached 1,200: F in 6 to 8
minutes [Brannigan 1999]. Table D-1 illustrates that steel retains only 25% of its original strength at 1,200: F and retains only half its original strength at approximately 900 :F. Building design calculations are based on original strength at normal temperatures. At
elevated temperatures, steel may retain no excess strength.

...steel loses strength when exposed to temperatures commonly found in structural fires. Steel has a high thermal conductivity, which means it can transfer heat away from a localized source and act as a heat sink. As long as the flame impingement is localized, the steel can transfer heat to other regions of the member-and thus the time to reach the critical temperature is delayed. If an intense fire is evenly distributed along the steel member, the critical temperature may be reached very quickly. Steel also has a high coefficient of expansion that results in the expansion of steel members as they are heated. As an example, a 50-foot-long steel beam heated uniformly over its length from 720 to 9720 F will expand in length by 3.9 inches. The same beam uniformly heated to 8000 F would expand by 3.2 inches; if heated to 1,2000 F, the beam would expand by 4.9 inches [Grundahl 1991; Cotes 1997].

 

[triforcharity]

I suspect it's because it's the only facial hair that can be worn that doesn't interfere with the use of S.C.B.E. (Self Contained Breathing Equipment)

This is actually true. It has nothing to do with budget cutback, or anything of the sort.

NFPA regulations state that nothing shall obstruct the proper fit and use of the SCBA mask. This is why most firefighters that have facial hair, only have a stache.

I personally have a goatee, but only on the days that I do not work. I shave it if I do.

 

[ElMondoHummus]

I suspect it's because it's the only facial hair that can be worn that doesn't interfere with the use of S.C.B.E. (Self Contained Breathing Equipment)

This is actually true. It has nothing to do with budget cutback, or anything of the sort.

NFPA regulations state that nothing shall obstruct the proper fit and use of the SCBA mask. This is why most firefighters that have facial hair, only have a stache.

I personally have a goatee, but only on the days that I do not work. I shave it if I do.

Oh, you guys and your... reasonable answers!



I was thinking we'd get something wittier, like allusions to regular 70's "videotaping" nights, but nooooooo...

 

[ve2vfd]

I don’t think you understand how heat transfer in steel works.

Nah, only been fighting fires and teaching at the academy 20 years... I understand absolutely nothing of heat transfer...

Our scientists at ae9/11truth say that even if the steel had no fire protection then it was so massive that the columns would have absorbed all the heat without failing. It says so in our slide show.

Ahhh if your conspiracy guys, er I mean "scientists" made up crap then is HAS to be true! Darn, I must have imagined all these industrial buildings I saw with steel structures warped and twisted like pretzels by heat over the years... must have been hidden explosives in all of them!

Good grief!

Pat

 

[Telltale Tom]

Leap to conclusions much? Make ◊◊◊◊ up much?

A WTC fire in 1974(?) was limited to one floor and was contained by the sprinkler system until FDNY showed up yet the fire did structural damage to the truss system. (Cite on request)

Truss systems in fires kill people, including firemen. Firemen train for these fires. Read this:

So you are saying that if the fire protection to the trusses were damaged it would only last 6-8 minutes. So why did they last so long? And why did the columns fail first?

 

[Furcifer]

Oh, you guys and your... reasonable answers!
I was thinking we'd get something wittier, like allusions to regular 70's "videotaping" nights, but nooooooo...

You've overlooked the fact that NFPA stands for "National Firefighting Porn Association". The S.C.B.E. is just a cover story. The real reason is because they never know when they will be required to tickle some pink. You probably think the brass poles are for quick egress to the garage. Another common misconception.

 

[R.Mackey]

I'm not an expert in fireproofing but I know that the heat shields of Mercury/Gemini/Apollo-generation spacecraft kept the cargo cool by vaporizing during reentry. The process is called ablation and this web page kind of suggests ablation may be at work in some kinds of fireproofing. This makes sense since we know that fireproofing only has to work for it's hour rating.

Who knows what the residue looks like after the ablation capacity is used up.

http://en.wikipedia.org/wiki/Passive_fire_protection

Correct. As I posted in another thread, the melting temperature of the fireproofing is probably around 1300^oC, lower than the steel it's supposed to protect. But that's not the point. The point is that the heat flow through the material is very low. If the surface melts or otherwise falls off, it exposes new material underneath that is still at a lower temperature.

In spacecraft, the plasma cloud at reentry can reach temperatures in excess of 2000^oC -- but there's not that much heat content, because the air hitting it is rather thin. Some early re-entry systems used ablatives, with stubby-nosed projectiles actually preferable to sharp, streamlined ones, as in the heat shield of the Apollo capsules. This let the thermal protection system steadily boil off a gaseous cushion (this is the "ablation"), and it is that entrained gas layer, not the spacecraft itself, that hit the atmosphere, got heated to absurd temperatures, and then just... steadily blew away, carrying the heat with it.

This is why fire protection is rated for time, not for a specific temperature. It's all about heat. Truthers don't seem to understand heat at all.