The NIST report, start to finish

Originally posted by exponent
Why are you so intent on trying to be right on this one minor point? It is really utterly irrelevant as we are speculating about their intentions and you are trying to discredit them based on wording you dislike.

The fact of the matter is that they modelled the collision with publicly available data and managed to get a reasonable reproduction. If they had included office contents it would likely have been a very strong match as this would reduce the core column damage to the same as NISTs estimates, and reduce the opposite side penetration as well.

If you check the NIST report you will find that they admit that in order to analyze the impact of the plane on the south tower they needed to know the distribution of weight of the building, AND THEN THEY DIDN'T DO IT.

Go to a 8 ft sign post on the street and smack it hard with the palm of your hand and see what happens.The post deflects a little bit and then oscillates for a while. That is what the NIST says the south tower did.

There are THREE DIFFERENT REASONS for wanting accurate distribution of steel information on those buildings and the impact is probably the least of them but that information IS IMPORTANT. I emailed three people at Purdue about that simulation. Chris Hoffman responded and told me to contact Professor Sozen. I had already emailed him.

Sozen was in charge but I never got a response from him.

The distribution of steel is important to any supposed weakening from fire and what would happen in a collapse. The strength of that steel must be overcome for that building to come straight down.

psik

Originally posted by hooper
reply to post by ANOK

 

IF the trusses heated up enough to expand (something else you need to prove before your hypothesis is excepted),....

So you think that steel expanding when any heat is applied is only a hypothesis?

That is not what I said, you have comprehension difficulties it seems. I said IF the trusses heated up ENOUGH to expand ENOUGH to make any difference to anything. I never said they wouldn't expand.

Its not, it is a fact.

I know it is, and if you had comprehended what I said you would have known I know. You are too quick to react and reply, you fall all over yourself and make yourself look foolish.

And the expansion begins the moment the temperature of the steel exceeds its neutral temperature. A given piece of steel will be larger at 100 degrees than at 90 degrees. That is a fact. The difference may be minute, but there is a difference.

Again I never said there wasn't so your whole reply falls flat on it's face. Maybe you will read my post again in a different light now you know you misunderstood, probably not.

What is neutral temperature lol? You mean the ambient temperature it was at before being heated? You don't do to well with terminology do you? There is no 'neutral temperature'. BTW see I can play the semantics game also, with you it's easy.

So to sum up; yes steel expands, which I explained in the very post you misunderstood and was part of my explanation, the reason they would have sagged, if they did, is because they expanded and could not pull columns inwards. Re-read that last post again, before you replay to this, and maybe you will understand this time, probably not. You just look for stuff to nit pic, out of context, because you don't care about reading and understanding the post. Your job is to attack, isn't it?

Hooper, so many times you misunderstand what's being said, it's sad, you and Esdad. In fact you could be the same person, you make the same misunderstandings? But again that's your job isn't hooper?

Originally posted by Azp420
I've never looked at the trusses, and couldn't find what I was looking for in a quick google search, but could someone be so kind as to tell me if the trusses were coupled to the concrete slabs they were supporting? If so, at what distances (if not continuously)?

The trusses used the upper knuckle of the web elements protruding through the metal decking to form a composite floor with the concrete. They were a little over 3 feet apart. The floor section looked like this:

This would be the case if the trusses were simply supported at the columns. Correct me if I'm wrong, but I believe the column-truss connection was a fixed support.

I'm not sure what you mean by a fixed support, they were essentially hung off a steel channel with a couple of bolts. There were some additional strap anchors and vibration dampeners and NIST takes those into account, but they are probably not of enough significance to discuss.

These are images of NISTs truss reconstructions for the fire resistance test:



This is an image of the steel deck covering a truss knuckle, concrete would then cover this to a depth of about 4".


This is a schematic view of the trusses:


Hopefully this should be enough to answer your questions about the truss designs.

Originally posted by psikeyhackr
If you check the NIST report you will find that they admit that in order to analyze the impact of the plane on the south tower they needed to know the distribution of weight of the building, AND THEN THEY DIDN'T DO IT.

This is a totally different argument to what we were just discussing, and I don't see the evidence for it anywhere.

I know that accurate information is important, but we've already been through this. Enough information exists to build a relatively accurate model. Once you have completed this step you can request specific information on panel types, masses etc from them. They are much more likely to respond to a legal request for a small amount of non sensitive data than they are to dumping out their entire database and models.

There's no point constantly complaining about it, if you want to properly model the towers then you've got a huge task ahead of you. Your existing models seem to focus on two issues, and the information for improving these is available to you.

Hello. Mind if I jump into the debate?

I don't see why people are so persistent on debating the accuracy of that simulation, or sidetracking about how much the building swayed, or the concrete distribution of the buildings. If you need a reminder, the topic is about the NIST report.

As a support to exponents direction with this debate, I just want to add (some of you might know this already) that structural steel loses about 50% of its strength at 1100 deg. fahrenheit, and is at about 10% at 1800 deg. F.
www.engineeringtoolbox.com...

NIST research indicated that the temperature reached as high as 1832 deg. F. in some areas of the structures, as the fires was intensified by the jet fuel.

Isn't it thereby plausible that the weakened steel (coupled by 10 severed central columns) failed to carry the weight of the floors above? And when the floors above starts falling, it gains momentum which the floor below wasnt supposed to withstand. Making it collapse and further adding to the downwards momentum.

Originally posted by Insolent
Hello. Mind if I jump into the debate?

As a support to exponents direction with this debate, I just want to add (some of you might know this already) that structural steel loses about 50% of its strength at 1100 deg. fahrenheit, and is at about 10% at 1800 deg. F.
www.engineeringtoolbox.com...

Sure jump in. Try saying something meaningful. What does that temperature REALLY MEAN?

Doesn't it mean the steel rose to that temperature ALL OF THE WAY TO THE CENTER OF THE STEEL?

It's called the core temperature of the steel. So if the steel is TWO INCHES THICK that means the temperature ONE INCH INSIDE the steel is 1100 deg F. So when do we here how thick the steel was at the 81st floor of the south tower? Isn't the thickness going to affect how many TONS OF STEEL THERE WERE on the 81st level. There had to be enough steel to support another TWENTY NINE STORIES of the building.

So how could that much steel that thick get hot enough TO THE CORE in less than ONE HOUR?

Oh yeah, experts like Richard Gage keep forgetting to ask about that.

psik

Originally posted by psikeyhackr

Originally posted by Insolent
Hello. Mind if I jump into the debate?

As a support to exponents direction with this debate, I just want to add (some of you might know this already) that structural steel loses about 50% of its strength at 1100 deg. fahrenheit, and is at about 10% at 1800 deg. F.
www.engineeringtoolbox.com...

Sure jump in. Try saying something meaningful. What does that temperature REALLY MEAN?

Doesn't it mean the steel rose to that temperature ALL OF THE WAY TO THE CENTER OF THE STEEL?

It's called the core temperature of the steel. So if the steel is TWO INCHES THICK that means the temperature ONE INCH INSIDE the steel is 1100 deg F. So when do we here how thick the steel was at the 81st floor of the south tower? Isn't the thickness going to affect how many TONS OF STEEL THERE WERE on the 81st level. There had to be enough steel to support another TWENTY NINE STORIES of the building.

So how could that much steel that thick get hot enough TO THE CORE in less than ONE HOUR?

Oh yeah, experts like Richard Gage keep forgetting to ask about that.

psik

The elements in the steel trusses were not two inches thick. Take a piece of steel and fix both ends and put a big weight on top, Heat it, even a little above its neutral temperature and it will sag. Heat it alot and it will sag alot, Heat it enough and it will sag to failure.

reply to post by exponent


Thank you for that. It appears I was wrong and the trusses were actually simply supported.

So the concrete acted in composite with the truss? Was there any concrete failure under these large deflections?

Am I correct in saying the theory is that the P-delta effect in the columns (caused by them being laterally deflected from the sagging trusses) caused failure of the columns?

Pardon my ignorance.

Originally posted by hooper

Originally posted by psikeyhackr

Originally posted by Insolent
Hello. Mind if I jump into the debate?

As a support to exponents direction with this debate, I just want to add (some of you might know this already) that structural steel loses about 50% of its strength at 1100 deg. fahrenheit, and is at about 10% at 1800 deg. F.
www.engineeringtoolbox.com...

Sure jump in. Try saying something meaningful. What does that temperature REALLY MEAN?

Doesn't it mean the steel rose to that temperature ALL OF THE WAY TO THE CENTER OF THE STEEL?

It's called the core temperature of the steel. So if the steel is TWO INCHES THICK that means the temperature ONE INCH INSIDE the steel is 1100 deg F. So when do we here how thick the steel was at the 81st floor of the south tower? Isn't the thickness going to affect how many TONS OF STEEL THERE WERE on the 81st level. There had to be enough steel to support another TWENTY NINE STORIES of the building.

So how could that much steel that thick get hot enough TO THE CORE in less than ONE HOUR?

Oh yeah, experts like Richard Gage keep forgetting to ask about that.

psik

The elements in the steel trusses were not two inches thick. Take a piece of steel and fix both ends and put a big weight on top, Heat it, even a little above its neutral temperature and it will sag. Heat it alot and it will sag alot, Heat it enough and it will sag to failure.

But the NIST tested FOUR floor sections with trusses in furnaces for TWO HOURS with higher than expected loads and THEY DID NOT FAIL. But they didn't repeat the tests without fireproofing. NOW WHY IS THAT?

As long as they don't test without fireproofing they can CLAIM that was the culprit. But if the trusses without fireproofing still don't fail within an hour then they have a problem with the south tower coming down in less than an hour. It is SO SCIENTIFIC to not test the obvious.

psik

Originally posted by Insolent

As a support to exponents direction with this debate, I just want to add (some of you might know this already) that structural steel loses about 50% of its strength at 1100 deg. fahrenheit, and is at about 10% at 1800 deg. F.
www.engineeringtoolbox.com...

That is irrelevant. There is no evidence any steel got that hot, especially not enough to cause complete failure of a 110 story building.

Also that does not account for factor of safety. The whole building could lose 50% of it's strength, and it would still not collapse through the path of most resistance ignoring the laws of motion. A safety factor of at least x2 is required, but many parts of the structure would be much higher than that due to their design.

A 110 story building is not going to collapse from fires on a few floors, no matter how hot they got and whether trusses sagged or not.

Look at the whole picture in context.

Originally posted by Azp420
So the concrete acted in composite with the truss? Was there any concrete failure under these large deflections?

Yes, the upper knuckle failed, concrete cracked and spalled, and as web elements fail the sagging results in the problematic geometry.

Am I correct in saying the theory is that the P-delta effect in the columns (caused by them being laterally deflected from the sagging trusses) caused failure of the columns?

Pardon my ignorance.

First it is important to note that truss seats would fail too as they're not exactly the most robust of elements. Once these fail that decreases the lateral support on the outer wall. This is important in developing the type of inward deformation you're talking about. I don't know whether it would specifically be P-delta effects but you can figure out the rough moment force yourself easily enough. I would have to get a structural engineer to sign off on the specific attributes of collapse.

Originally posted by psikeyhackr
But the NIST tested FOUR floor sections with trusses in furnaces for TWO HOURS with higher than expected loads and THEY DID NOT FAIL. But they didn't repeat the tests without fireproofing. NOW WHY IS THAT?

This unfortunately has exposed your arguments for what they are, repeated from some conspiracy site without critical thinking.

NISTs theory is that the trusses did not fail, instead they sagged and pulled in on the outer wall. In NISTs tests even with fully fireproofed trusses there were element failures + concrete damage.

Of course, NIST also tested unfireproofed trusses for their thermal properties, exactly so they didn't have to recreate a bunch of different elements in fire and end up damaging their equipment lol. They performed these tests specifically as they were important in ensuring the WTC was sufficiently designed.

Originally posted by ANOK
A 110 story building is not going to collapse from fires on a few floors, no matter how hot they got and whether trusses sagged or not.

Lets list a few people who disagree with your opinion here:

1. Professor Zdenek P. Bazant, ISI highly cited scientist, holds 6 honorary doctorates and received the 2009 ASME Timoshenko Medal.
2. David Scott, Chairman of the Council on Tall Buildings. Leader of ARUP New York, participated in the Ground Zero cleanup
3. Professor James Quintiere, Chairman for the International Association for Fire Safety Science, believes the WTC could have collapsed without fireproofing damage
4. Dr Shyam Sunder, former MIT professor and holds a doctorate in structural engineering from MIT, received a Gold Medal Award for his work on the NIST report and served on the ASTM international board of directors

This is a pretty significant list and so I take issue with you invoking your own opinion to try and disprove the collapses. Here are 4 people who's credentials are pretty obvious and they all disagree with you.

Originally posted by ANOK

Originally posted by Insolent

As a support to exponents direction with this debate, I just want to add (some of you might know this already) that structural steel loses about 50% of its strength at 1100 deg. fahrenheit, and is at about 10% at 1800 deg. F.
www.engineeringtoolbox.com...

That is irrelevant. There is no evidence any steel got that hot, especially not enough to cause complete failure of a 110 story building.

Also that does not account for factor of safety. The whole building could lose 50% of it's strength, and it would still not collapse through the path of most resistance ignoring the laws of motion. A safety factor of at least x2 is required, but many parts of the structure would be much higher than that due to their design.

A 110 story building is not going to collapse from fires on a few floors, no matter how hot they got and whether trusses sagged or not.

Look at the whole picture in context.

No, it is very relevant.

wtc.nist.gov...

Please look at #4, 6, 7-14 and 21. All fire related based on their research.

Also, your opinion is not fact no matter how many times you repeat it.

Originally posted by exponent

Originally posted by psikeyhackr
But the NIST tested FOUR floor sections with trusses in furnaces for TWO HOURS with higher than expected loads and THEY DID NOT FAIL. But they didn't repeat the tests without fireproofing. NOW WHY IS THAT?

This unfortunately has exposed your arguments for what they are, repeated from some conspiracy site without critical thinking.

NISTs theory is that the trusses did not fail, instead they sagged and pulled in on the outer wall. In NISTs tests even with fully fireproofed trusses there were element failures + concrete damage.

Of course, NIST also tested unfireproofed trusses for their thermal properties, exactly so they didn't have to recreate a bunch of different elements in fire and end up damaging their equipment lol. They performed these tests specifically as they were important in ensuring the WTC was sufficiently designed.

So now you want to quibble about words.

They only SAGGED 14 inches in the furnaces. All of the TALK in the NIST report of what the floors did in the buildings is NOTHING BUT SPECULATION. But the sections that tested in furnaces had insulation. So the SCIENCTIFIC thing to do would be to test them without insulation. So why haven't they done something that obvious.

Because if the don't SAG or FAIL under those conditions then the NIST will be proven to be idiots.

This is what the report says:

Additionally, the four Standard Fire Tests (ASTM E 119) of floor assemblies like those in the WTC towers showed that the load carrying capacity of the short span 35 ft floor system with a 0.75 in. insulation thickness was not compromised by heating for two hours at furnace temperatures with applied loads that exceeded those on September 11, 2001 by a factor of two. It took about 90 minutes of sustained heating in the furnace for temperatures to exceed 600 °C on steel truss members with either ½ in. or ¾ in. insulation thickness. The high temperature conditions in the furnace tests were at least as severe and lasting as long as the WTC fires, although the top of the slab was not heated. Although some web members buckled and the floor test assembly sagged up to 14 in. during the tests, the insulation remained intact during the tests.

NISTNCSTAR1-6

So you provide evidence that they tested trusses without insulation.

psik

reply to post by psikeyhackr


Actually,out of the 4 assemblies they used, one was not totally covered in SFRM. The bridging trusses were not coated and protected from over spray.

4.3.1 Table 4 of the NCSTAR 1-6B is where it is explained.

Also, on page 4 of the document, there is a nice mention of the original design plan and why they performed test #4.

There's your proof. Read the results.

Originally posted by esdad71
reply to post by psikeyhackr

 

Actually,out of the 4 assemblies they used, one was not totally covered in SFRM. The bridging trusses were not coated and protected from over spray.

4.3.1 Table 4 of the NCSTAR 1-6B is where it is explained.

Also, on page 4 of the document, there is a nice mention of the original design plan and why they performed test #4.

There's your proof. Read the results.

So is somebody claiming when the impact knocked off the fireproofing it only knocked it off the bridges?

None of the tested sections failed. Until they test a bare floor component AND IT FAILS nothing has been accomplished. If they test a bare one and it DOES NOT FAIL then all of this talk about missing fireproofing causing the problem is RUBBISH.

What do you think you are accomplish by brining up a partially bare floor assembly that STILL DID NOT FAIL? I am not even going to research it because none of them failed. If anything you just hurt your own case.

psik

Originally posted by hooper

Originally posted by psikeyhackr

Originally posted by Insolent
Hello. Mind if I jump into the debate?

As a support to exponents direction with this debate, I just want to add (some of you might know this already) that structural steel loses about 50% of its strength at 1100 deg. fahrenheit, and is at about 10% at 1800 deg. F.
www.engineeringtoolbox.com...

Sure jump in. Try saying something meaningful. What does that temperature REALLY MEAN?

Doesn't it mean the steel rose to that temperature ALL OF THE WAY TO THE CENTER OF THE STEEL?

It's called the core temperature of the steel. So if the steel is TWO INCHES THICK that means the temperature ONE INCH INSIDE the steel is 1100 deg F. So when do we here how thick the steel was at the 81st floor of the south tower? Isn't the thickness going to affect how many TONS OF STEEL THERE WERE on the 81st level. There had to be enough steel to support another TWENTY NINE STORIES of the building.

So how could that much steel that thick get hot enough TO THE CORE in less than ONE HOUR?

Oh yeah, experts like Richard Gage keep forgetting to ask about that.

psik

The elements in the steel trusses were not two inches thick. Take a piece of steel and fix both ends and put a big weight on top, Heat it, even a little above its neutral temperature and it will sag. Heat it alot and it will sag alot, Heat it enough and it will sag to failure.

Yeah look at pictures of the tilted top portion of the south tower. Didn't all of the core columns and all of the perimeter columns have to BREAK for the top of the south tower to get into that position?



Sure blame all of those broken columns on how thin the steel was in the trusses.

psik

reply to post by ANOK

What is neutral temperature lol? You mean the ambient temperature it was at before being heated? You don't do to well with terminology do you? There is no 'neutral temperature'. BTW see I can play the semantics game also, with you it's easy.

Temperature of the steel when it was fixed. The trusses were fixed at both ends. That and the weight they were carrying were the reason they sagged and not blew out threw the side of the exterior wall.

Hooper, so many times you misunderstand what's being said, it's sad, you and Esdad. In fact you could be the same person, you make the same misunderstandings? But again that's your job isn't hooper?

Typical. Your lack of writing skills are never in question, huh? Just a coincidence that everybody "misunderstands" you the same way.