An email from a Conspiracy theorist, and I have no idea how

[Heiwa]

So ? Do you have any idea how much fire weakens steel ?



You're not very good at this.

The sagging was due to HEAT, not excess loads. The floors were NOT disconnected from the columns and that's the WHOLE point. Because they weren't, they pulled on the columns.



You only need ONE wall to fail to initiate collapse. In fact, you can see the top section of 2 WTC tilt at the beginning. Then the strain snaps the remaining columns and the whole thing comes down. Dammit, man. You can see this on the videos quite clearly.




[qimg]http://www.internationalskeptics.com/forums/imagehosting/thum_608045892c4f64e35.jpg[/qimg]



The theory explains what happened and is supported by VISUAL evidence. What do you need ? A signed document from the Maker confirming this ?



Please tell us how much time it would take, and the exact percentage of redistribution...



Begging the question.



Again, please explain the following:

1) What kind of demolition charge produces no explosion and no sound ?
2) How can 47 columns fail simultaneously and STILL result in the top section tilting as it fell ?
3) How do you know the core failed first since we can clearly see it collapse LAST ?
4) What kind of explosive can caused the extreme bowing seen in this photograph ?

[qimg]http://www.internationalskeptics.com/forums/imagehosting/thum_608045892c65f25a4.jpg[/qimg]



Nonsense. Thousands of engineers and scientists around the world, with no affiliation to the US government, would be able to spot the discrepancies.



Toughen up.

I don't know how to quote above with sub-quotes but here we go.

There was no load on the floors above, except their own weight + furniture. Why concrete floors + steel trusses would then sag due to heat is beyond me but it will not be much. I know steel expands due to heat ... but concrete!! No way. The floors were >95% concrete. And that combination supported the perimeter columns regardless of any sagging.

Sorry - one (east) wall - supporting only 12.5% of the total load cannot initiate total global collapse. Why - the other structure, particularly the core, will easily support the load transferred to it. Basic. It is seen on the photos! The east wall is deformed ... and the other parts are intact. The tower stands.

And suddenly the whole thing explodes! But videos of the roof - far above - shows that it sags a little before that = the 47 core columns apparently failed before the east wall. Similar to WTC7? Strange case. But support for Controlled Demolition.

It would have been easy to check why the 47 off 400 metres tall core columns failed by proper forensic examination. But it was not done. This is why I suspect an Inside Job. And it is easiest decided by a re-hearing of the whole case in a law court. I actually believe in the Law of Justice. Do you?

 

[Panoply_Prefect]

Umm arent these supposed to be pictures of the sagging floors:

 

[DavidJames]

I actually believe in the Law of Justice. Do you?

I believe in evidence and you've presented nothing but an argument from incredulity. Which means nothing to science, engineering and the court of law.

But please come back when you are able to present something tangible.

 

[uk_dave]

Good grief, it gets worse.

Let's try some imaginary scenarios:

First, let's say we have a beam that is spanning across a void 3.0m wide. For the sake of argument will say it is 152x152mm UB.

Now this beam is nice and flat and when we stand on it it doesn't move a millimetre. Lovely beam it is. We like this beam.

Now, we have an endless supply of beams like this, only in varying lengths. And because we like it so much, we decide to use a similar beam to span across a void 30 metres wide.

But this time we're not so happy. Can anyone tell me why?

..................

We've learned our lesson from the unhappy experience with the 30.0m beam and now we've got all clever and stuff and we've figured out how to span that distance using our favourite beams. We'll use two of them!! Aren't we clever?

Even clevererer we'll have one baem above the other and we'll connect them together with struts and braces until we have a very pretty beam indeed. We're feeling very good now.

We span our new sooper dooper beam across the void and it's solid and steady and ohhhh so fantastic, so it is.

But we really need to hold it in place with something because sometimes, when we've had a very very hot curry and we're standing on our beam, it starts to wobbly. oooooooo scarey.

So we get another couple of our most favourite beams and this time we put them upright. They look so good like that. We put one at each end of our sooper dooper beam and we fix it all together with magic fairy nuts.

ooooooooo we are soooooo clever. The most clererest thing in the whole whole..... but wait. What's this? An evil troll is in the void just under our lovely beam. And he's cooking his socks! What a smelly old troll he is. And what a big fire he has built. The flames are almost touching our beam.

But we're not scared are we boys and girls? Noooooooo. We can stand on the middle of our beam and blow rasberries at the smelly troll because he can't reach us.

But then we feel our beam begin to move. What's happening? Oh my, the fire is somehow making our beam go weak. But, not to worry, because it is safely fixed at both ends and can't fall on top of the smelly troll.

But wait...oh no!!! the eccentric forces applied to the upright members is causing them to rotate about their axis, and the fairy nuts aren't letting go!!

Help! Help! we cry, as our beam sags more and more and the fire starts to touch our toes and then, with a crack and a bang and a whoosh and a twang, our beam and our posts tumbles down into the trolls fire.

And we're sad, because the troll is now applying barbeque sauce to our nether regions.

Goodnight boys and girls.

 

[Newtons Bit]

There was no load on the floors above, except their own weight + furniture. Why concrete floors + steel trusses would then sag due to heat is beyond me but it will not be much. I know steel expands due to heat ... but concrete!! No way. The floors were >95% concrete. And that combination supported the perimeter columns regardless of any sagging.

Annnnnnnnd you just proved to me that you know nothing about structural engineering. Let's explain some concepts that you should have picked up in the second or third year of your undergraduate program:

The concrete slab in the WTC was composite with the floor trusses, which means that they acted together to resist bending moments. This translates to the concrete slab and the top chord of the truss being in compression, and the bottom chord of the truss in tension. Fairly basic concept for most people, you seem to be implying that the concrete did most of the work in holding the floors up.

The important point here, is how steel behaves when it is heating. You think that it only expands. Probably something you picked up watching a cooking show on TV. Something else important thing that changes is the modulus of elasticity. This modulus is the ratio of pressure to percent deformation. When the steel heats up, the modulus of elasticity goes down. So the bottom chord expierences higher amounts of elongation, hence sagging. This is immediately obvious to anyone who took a basic course in mechanics of materials, which you've either forgotten or never took.

There's something else that happens with the above, since the top chord is in compression and the bottom chord is tension, any increase in heat would result in strain compability issues with the web members. The web, being welded to the top and bottom chord of the truss, will be stretched as the bottom chord elongates and the top chord shrinks.

The above is probably the first explanation most engineers would come to when looking at a bending member that sagged due to heat. However it is not the only one.

The second one that comes to mind is the change in the yield stress of the truss due to heat. If the truss yields, then it will elongate a great deal without any further increase in stress. Also a basic concept.

There are more explanations as well:

Any damage to the web members of the truss would result in the top chord becoming more of a bending member than an axial only member. This will cause the stress in the top chord to increase and might even cause it to yield.

Localized point loads from very heavy objects (large pieces of the planes or debris from above) can overload the shear capacity of the truss. This would likely have the biggest effect if the point load was near the middle of the span of the truss as that is where an economical design will have the smallest web members.

Any large deflection in the truss, probably in the range of L/180 would crack the floor slab, further lowering the strength of the composite floor. Furthermore, floor slabs are NEVER used to brace steel columns as concrete has no tensile capacity. The only thing that braced the columns were the floor members.

 

[Heiwa]

Annnnnnnnd you just proved to me that you know nothing about structural engineering. Let's explain some concepts that you should have picked up in the second or third year of your undergraduate program:

The concrete slab in the WTC was composite with the floor trusses, which means that they acted together to resist bending moments. This translates to the concrete slab and the top chord of the truss being in compression, and the bottom chord of the truss in tension. Fairly basic concept for most people, you seem to be implying that the concrete did most of the work in holding the floors up.

The important point here, is how steel behaves when it is heating. You think that it only expands. Probably something you picked up watching a cooking show on TV. Something else important thing that changes is the modulus of elasticity. This modulus is the ratio of pressure to percent deformation. When the steel heats up, the modulus of elasticity goes down. So the bottom chord expierences higher amounts of elongation, hence sagging. This is immediately obvious to anyone who took a basic course in mechanics of materials, which you've either forgotten or never took.

There's something else that happens with the above, since the top chord is in compression and the bottom chord is tension, any increase in heat would result in strain compability issues with the web members. The web, being welded to the top and bottom chord of the truss, will be stretched as the bottom chord elongates and the top chord shrinks.

The above is probably the first explanation most engineers would come to when looking at a bending member that sagged due to heat. However it is not the only one.

The second one that comes to mind is the change in the yield stress of the truss due to heat. If the truss yields, then it will elongate a great deal without any further increase in stress. Also a basic concept.

There are more explanations as well:

Any damage to the web members of the truss would result in the top chord becoming more of a bending member than an axial only member. This will cause the stress in the top chord to increase and might even cause it to yield.

Localized point loads from very heavy objects (large pieces of the planes or debris from above) can overload the shear capacity of the truss. This would likely have the biggest effect if the point load was near the middle of the span of the truss as that is where an economical design will have the smallest web members.

Any large deflection in the truss, probably in the range of L/180 would crack the floor slab, further lowering the strength of the composite floor. Furthermore, floor slabs are NEVER used to brace steel columns as concrete has no tensile capacity. The only thing that braced the columns were the floor members.

So what? The vertical load on the floor assembly was only 20 kgs/m² = furniture and outfitting. No heavy members of an alleged plane landed on the floor! All that material flow in and out of the windows at once. If it was a plane? To me most fuel - 30 tons - also disappeared through the windows - at once. Why would the fuel stop inside the building, if it arrived at 800 kms/h? To me the impact looks like an explosion ... and not a plane impact. A plane impact would look completely different.

It is alleged that the temperature was high, so the steel and the concrete warmed up and material properties changed. And that the floors above impact sagged. But where is the evidence? As soon as the temperature falls again (the fire fades - only 20 kgs/m² of furniture burning you know) the material properties return to normal and the floor - even if deformed and with some cracked concrete - becomes an effective support again. The connections to the columns are still intact, i.e. the columns' supports are effective. And that accounts for 80% of the columns according NIST.

It seems on most photos that the fire was gone long before the sudden collapse ... that ensued. The small fires we see on photos are negligible. Just to roast a chicken on! So I assume most heat had escaped with the smoke, the temperature had fallen as fresh air was sucked in. It was not a big space and open all around. All columns in the south, west and north walls were effective then again before the collapse and could carry the 10-15% extra load from the failed east wall. So no global, sudden collapse could ensue. The mistake of NIST is that they ignore many things, e.g. that the temperature falls again, that the structure, even if damaged becomes more effective again, etc. But they were too afraid to admit it.

What a sloppy explanation of the collapse. It just ensued.

 

[The Almond]

[...]
I know steel expands due to heat ... but concrete!! No way. The floors were >95% concrete. And that combination supported the perimeter columns regardless of any sagging.
[...]

I would highly suggest reading any book on concrete. Mindness, Young and Darwin in Concrete 2nd edition list the coefficient for thermal expansion in concrete as between 7.4/C and 13/C. It lists the coefficient of thermal expansion for steel as between 11/C and 12/C. The PCA's Design and Control of Concrete Mixtures lists the value as 10/C. Jack McCormac's Design of Reinforced Concrete lists the value for reinforced concrete as between 9/C and 12/C.

So to answer your question, yes, concrete does indeed expand, deform and sag under load. The only appreciable difference between steel and concrete is in ductility and toughness, not in thermal expansion.

 

[Alferd_Packer]

Heiwa, a short and simple paper for your reading enjoyment:

http://fire-research.group.shef.ac.uk/Downloads/SC_Baltimore.pdf

(don't forget about my question regarding the DCRs)

 

[Newtons Bit]

OT but an easy one answered by Euler already 1744. The critical load P is

P = pi² x E x I / L² where L is the unsupported length of the column.

So if P = 100% when L is one unit, it is 25% when L is two units, it is 11.11 % when L is three units, etc. This is basic! Didn't you know Euler?

So you don't believe in inelastic buckling? Perhaps your studies in structural analysis would have led you to the path of Shanley and true column behavior, but ah well. Column buckling wasn't figured out until the middle of the 20th century. Euler buckling is only correct for extremely slender columns.

If you actually did REAL structural analysis, you would know this.

 

[maccy]

The small fires we see on photos are negligible. Just to roast a chicken on! So I assume most heat had escaped with the smoke, the temperature had fallen as fresh air was sucked in.

Why did people jump from the building if the fires weren't hot?

And where did all that smoke come from?

 

[Heiwa]

So you don't believe in inelastic buckling? Perhaps your studies in structural analysis would have led you to the path of Shanley and true column behavior, but ah well. Column buckling wasn't figured out until the middle of the 20th century. Euler buckling is only correct for extremely slender columns.

If you actually did REAL structural analysis, you would know this.

Of course - I was just testing this fool Alferd. And I like basics. But this is OT. We are discussing the NIST load re-distribution theory after alleged buckling of the east wall due lack of support and what happens to the core columns. OK - the core columns were not slender at all - some were box shaped - quite strong - why did they suddenly collapse? Did they buckle, compress, go up in smoke? You agree with NIST? Were they only softened?

Have you seen the core columns arrangement of WCT2? I was there a couple of times before the collapse on various floors. Looked very strong.

 

[Newtons Bit]

Heiwa, click the link below my post. I have actually calculated the compressive strength of the columns near the plane impact. It's overly conservative in favor of collapse prevent because it's based on Gordon Ross's assumptions.

If you REALLY knew what Euler buckling was, you wouldn't have used the I term, you would have used the more generic and modern (KL/r).

If you claim to be an engineer, use some actual engineering to make your arguments. Don't just use things you find on google, actually take the time to write a real paper with a real mathematical model. All your doing now is blowing smoke out of your filing cabinet.

 

[Heiwa]

In my comment #49 I quoted the NIST suggestion how global collapse ensued due to a small load distribution, which I queried. Nobody has so far explained why a small load distribution caused total collapse, so I assume we all agree that NIST suggestion is wrong. Most respondents have queried my knowledge about basic structural strength etc., which is of course OT.

But NIST is quite specific what happens when the east wall buckles and before total collapse ensues:

"The section of the building above the impact zone tilted to the east and south (observed at about 7° to 8° to east and about 3° to 4° to south, (…) as column instability progressed from the east wall to the adjacent south and north walls. The release of potential energy due to downward movement of the building mass above the buckled columns exceeded the strain energy that could be absorbed by the structure. Global collapse ensued (sic)."

So now we turn from structural analysis to pure mechanics and dynamics.

Thus - due to the east wall collapse that started at time T and before global collapse ensued at time T + t1, i.e. in t1 seconds, the section above the impact zone tilted 7-8° to east due to release of potential energy. Assume that the section above is 100 metres high with its centre of gravity, CoG, at 50 metres above the impact zone. This means that the CoG of the section above shifted abt 6.14 metres to the east and the top of the lose section 12.28 metres to the east during time t1, before it started to fall straight down, when the south, west and north walls and the centre core collapsed - disappeared.

What is the rate of tilting (°/s) of the section above the impact zone at time t1. It was 0 °/s at time T but what was it at time t1? 15 °/s or more? As many observers have pointed out the section above the impact zone was completely undamaged and should evidently continue to rotate or tilt as it falls down. Its rotating momentum cannot be stopped.

How long time, t2, does it take for the undamaged section above the impact zone to fall down to the ground. Say its CoG was 350 metres above ground. Say that t2 is 8 seconds. How much should the 100 metres tall section above the impact zone rotate/tilt in that time? 120° or 90°? Did it? Or did it disappear in smoke?

You also wonder how the west part of the tower below the impact zone collapsed as there was no weight - potential energy - released above it. The potential energy that caused collapse - the intact section above the impact zone - was evidently shifting is CoG to east during the collapse. The CoG of section above the impact zone must in the end have been east of the east wall.

Regardless - the undamaged section above the impact zone obviously lands on top of rather on the east side of the remains of the tower that globally collapsed (for unknown reasons) below it.

Did it? I assume that the undamaged section above the impact zone should have landed more or less on its east wall side with the west wall on top, i.e. after the total collapse of the tower, we should have observed 100 metres of west wall columns on the east side of or on top of the rubble.

This 80 x 100 metres west wall column assembly should be more or less intact before it hits the ground/rubble on the ground and should then deform a little. It should have been easy to document this section. It was on top of everything.

Did anybody? Under the 100 metres of west wall columns, we should find 100 metres of 47 centre core columns, etc. They should be more or less continuous, i.e. one piece each but maybe deformed. It would have been easy to see how these core columns were torn apart at the impact zone.

But strangely enough it was not done. No forensic examination was done of section above the impact zone. It seems, which many observers have noted, that the intact section above the impact zone - four walls and its core - disintegrated in air between times t1 and t2. How to explain that? NIST does not explain it.

 

[Heiwa]

Do you believe that airliners hit the Twin Towers, the Pentagon, and a field in Pennsylvania on 9/11?

Good question. As I didn't see the incidents in person, I can only study the effects (holes in WCT1,2, Pentagon and a Pennsylvania field and rubble everywhere) and try to establish what caused them. Witnesses have given many different testimonies of what happened just before the impacts so I leave that analysis to others. It seems that forensic documentation of parts from any objects hitting the various locations is sloppy, so I have given up analysis of that too.

Subject here is of course the alleged by NIST load redistribution in WTC2 long after impact and what happens then. I have my doubts that global collapse ensued due to load redistribution as described by NIST, so what caused the global collapse? And how did the intact section above the impact zone get damaged, etc. It was the potential energy released, but it seems it flew away eastward during the collapse.

 

[stateofgrace]

Good question. As I didn't see the incidents in person, I can only study the effects (holes in WCT1,2, Pentagon and a Pennsylvania field and rubble everywhere) and try to establish what caused them. Witnesses have given many different testimonies of what happened just before the impacts so I leave that analysis to others. It seems that forensic documentation of parts from any objects hitting the various locations is sloppy, so I have given up analysis of that too.

Really ? I guess it is beyond your wildest dreams that planes that were hijacked by Islamic terrorists were the cause of all the death and destruction? I guess we should start to look for hidden explosives, missiles, maybe planes that flew over the buildings or hey maybe we should question whether sinister top secret US black guys staged it all in order to gain public support for the war on terror eh ?

Your analysis to date is one of wild speculation, based on wishful thinking and a desire to be oh so clever and spot something that the entire planet missed. You have failed, you have not spotted anything because there is nothing to spot other than your small anomalies that goes with every large event. An event that you and your like minded buddies wish to be a part of, you wish the importance that comes with this event upon yourself, again you will fail because you are not important, you are just some guy who plays at being the internet detective when the rest of the planet has moved on.

I guess the truth really is too terrifying for you, that being we really are hated , hated enough for 19 guys to board four planes, kill all their path and slam three of them into buildings full of innocent people. Is that enough truth for you ? Or did you actually fail to get the message that was sent to you on 911?I guess you did.

Subject here is of course the alleged by NIST load redistribution in WTC2 long after impact and what happens then. I have my doubts that global collapse ensued due to load redistribution as described by NIST, so what caused the global collapse? And how did the intact section above the impact zone get damaged, etc. It was the potential energy released, but it seems it flew away eastward during the collapse.

Really? and where exactly do you expect a massive dynamic weight that is falling on floor trusses to go? Just how on earth do you expect the floors that simply braced the external columns to core to support it ?

The core survived the collapse, the floors and the external columns did not, why oh why do you have such a difficult time with such a simple process. The weight fell on the floors,the floors were violently ripped away from the inner core and the external columns. The core collapsed later.

SIMPLE.

Oh wait maybe not, lets look at explosives, thermite, secret death squads, fires that could not possibly cause any further damage to a already damaged steel framed structure and while we are at it lets investiagte Flight 77 not hitting the Pentagon but actually flying over it . Oh wait theres more, lets all say the desperate calls from the passengers on flight 93 were faked, as was the crash site. Wow lets just make up all sorts of nonsense and pretent we are all self important.

Yeah sure, what ever you say Mr Offshore Structural Engineer ( not).

 

[Dog Town]

The small fires we see on photos are negligible. Just to roast a chicken on!

You must have acre sized BBQ's, per chicken. Are you for real?

 

[Heiwa]

Heiwa, click the link below my post. I have actually calculated the compressive strength of the columns near the plane impact. It's overly conservative in favor of collapse prevent because it's based on Gordon Ross's assumptions.

If you REALLY knew what Euler buckling was, you wouldn't have used the I term, you would have used the more generic and modern (KL/r).

If you claim to be an engineer, use some actual engineering to make your arguments. Don't just use things you find on google, actually take the time to write a real paper with a real mathematical model. All your doing now is blowing smoke out of your filing cabinet.

Interesting link. So there are two possibilities - global collapse ensues (NIST) or global collapse should have been prevented (and something else initiated the collapse). Anyway - global collapse was prevented for some time, so the structure was not too bad ... until it suddenly disintegrated due load redistribution. It is a pity that a forensic analysis was nor carried out of the structural parts in question. Of course I am an engineer, but I try to explain matters in layman terms for easy understanding. It is very practical when working in the field with welders and platers, etc. I can do 3D FEM/beam analysis, etc. but the input has to be correct, e.g. the actual conditions and loads. And NIST establishing actual conditions and loads is sloppy. And then it is very easy to chose some assumed conditions and loads to achieve the given result. I have seen it before.

Interesting reactions on this forum. Many believes anything and do not like open discussions.

 

[Heiwa]

Really ? I guess it is beyond your wildest dreams that planes that were hijacked by Islamic terrorists were the cause of all the death and destruction? I guess we should start to look for hidden explosives, missiles, maybe planes that flew over the buildings or hey maybe we should question whether sinister top secret US black guys staged it all in order to gain public support for the war on terror eh ?

Your analysis to date is one of wild speculation, based on wishful thinking and a desire to be oh so clever and spot something that the entire planet missed. You have failed, you have not spotted anything because there is nothing to spot other than your small anomalies that goes with every large event. An event that you and your like minded buddies wish to be a part of, you wish the importance that comes with this event upon yourself, again you will fail because you are not important, you are just some guy who plays at being the internet detective when the rest of the planet has moved on.

I guess the truth really is too terrifying for you, that being we really are hated , hated enough for 19 guys to board four planes, kill all their path and slam three of them into buildings full of innocent people. Is that enough truth for you ? Or did you actually fail to get the message that was sent to you on 911?I guess you did.





Really? and where exactly do you expect a massive dynamic weight that is falling on floor trusses to go? Just how on earth do you expect the floors that simply braced the external columns to core to support it ?

The core survived the collapse, the floors and the external columns did not, why oh why do you have such a difficult time with such a simple process. The weight fell on the floors,the floors were violently ripped away from the inner core and the external columns. The core collapsed later.

SIMPLE.

Oh wait maybe not, lets look at explosives, thermite, secret death squads, fires that could not possibly cause any further damage to a already damaged steel framed structure and while we are at it lets investiagte Flight 77 not hitting the Pentagon but actually flying over it . Oh wait theres more, lets all say the desperate calls from the passengers on flight 93 were faked, as was the crash site. Wow lets just make up all sorts of nonsense and pretent we are all self important.

Yeah sure, what ever you say Mr Offshore Structural Engineer ( not).

Thank you but you are 200% OT as we discuss another matter - alleged load re-distribution and its effects on WTC2.

 

[stateofgrace]

Interesting link. So there are two possibilities - global collapse ensues (NIST) or global collapse should have been prevented (and something else initiated the collapse). Anyway - global collapse was prevented for some time, so the structure was not too bad ... until it suddenly disintegrated due load redistribution. It is a pity that a forensic analysis was nor carried out of the structural parts in question. Of course I am an engineer, but I try to explain matters in layman terms for easy understanding. It is very practical when working in the field with welders and platers, etc. I can do 3D FEM/beam analysis, etc. but the input has to be correct, e.g. the actual conditions and loads. And NIST establishing actual conditions and loads is sloppy. And then it is very easy to chose some assumed conditions and loads to achieve the given result. I have seen it before.

Interesting reactions on this forum. Many believes anything and do not like open discussion s.

That is because I am close minded and beleive every single thing that my Government tell me, I am a sheep you see, I simply all fall in and obey the NWO. Oh Wait...............

Maybe , just maybe all your bunk as already been debunked , maybe just maybe that people actually find it quite offensive when internet detectives start accusing perfectly innocent people of being involved in mass murder.

You see, sunbeam you are actually acussing your fellow countrymen of mass murder and trying to excuse the real terrorists who committed this wicked act. So my learned fellow offshore worker( not) maybe you can start your open discussion by explaining to me why on earth I should listen to a word you say. Why should I listen to somebody who is trying to tell me that every single event that took place on 911 is not as it seems? You are the detective you are the one doing all the investigating , not me, I have no such delusions of grandeur, this is because I believe everything I am told, oh wait...... except your bunk that is.

So in the spirit of fair play and open discussion why don't you tell me what happeend on 911, no more "I'm just asking questions", no more sliding out of it, a simple summary of the day events. It goes something like this.

" On 911 four planes were hijacked by Islamic terrorists, two hit the towers, which burnt and then fell down. They fell on top of other buildings , which also fell down. A third plane hit the Pentagon and the forth crashed after the passengers fought back. A Group called Al Qaeda have repeadley claimed responsibility for this attack"

Now that is a simple summary, please offer up your own, do not have a go at mine, after all I am just a sheep who buys into anything, so why don't you tell , in your own words what happened?

 

[Lurker]

I can do 3D FEM/beam analysis, etc. but the input has to be correct, e.g. the actual conditions and loads. And NIST establishing actual conditions and loads is sloppy. And then it is very easy to chose some assumed conditions and loads to achieve the given result. I have seen it before.

You have actually seen the details behind the FEA? Have you seen how they arrive at the assumptions of boundary conditions and loads?

In your FEMs, do you perform coupled heat transfer/structural analysis?

Lurker