structural engineer leslie robertson interview

Originally posted by Arsenis


sure lets say it happen that way but the problem is all the anomalies that went on that day, first of all collapse, fine i get it the fires weakened the structure but it would have not fallen the way it did and what are the chances that not only happened 2 times but actually 3 times.

now with WTC 7 it backs up theories of the towers being brought down, the towers collapse would not have fallen the way it did, not into itself and like i said, fine lets say it happen once but a second time just the way it happen before as if the damage to the 2 towers was the same which wasn't and WTC 7 should have fallen similar to this video.

Watch around 1:45 to 2:05.

How do you get that they happened identically?

I saw three different and distinct collapses.

South Tower - Upper Floors toppeld to the left before falling down on top of the rest of the building

Noth Tower - upper floors dropped almost straight down.

WTC7 - Fracture across the width of the entire structure outside curtain wall collapse with roof toppling in on the central support.

[edit on 18-3-2009 by Achorwrath]

Originally posted by Achorwrath
South Tower - Upper Floors toppeld to the left before falling down on top of the rest of the building

And how do you explain how this happened? You obviously haven't looked into to hard.

The top of WTC 2 was experiencing 'angular momentum' when it was tilting.

The angular momentum of an isolated system remains constant in both magnitude and direction. The angular momentum is defined as the product of the moment of inertia I and the angular velocity. The angular momentum is a vector quantity and the vector sum of the angular momenta of the parts of an isolated system is constant. This puts a strong constraint on the types of rotational motions which can occur in an isolated system. If one part of the system is given an angular momentum in a given direction, then some other part or parts of the system must simultaneously be given exactly the same angular momentum in the opposite direction. As far as we can tell, conservation of angular momentum is an absolute symmetry of nature. That is, we do not know of anything in nature that violates it.

Read that and understand it. Then explain how the angular momentum of the top changed to vertical momentum. How can the top, when in angular momentum, it's force is not in the vertical plane, suddenly decide to go straight down? The only way that could have happened is if the bottom, independently collapsed from under the top. In fact you can see this if you look at the vid real close, the top suddenly has no pivot point for it's tilt, so it has no choice but to drop following the collapsing bottom section of the building.

Falling bodies will always follow the path of least resistance, that's why the top tilted in the first place, if it had the energy to collapse the building under it it would have done that immediately, not while undergoing angular momentum.

Also the building had held the top since it was built, how did it suddenly get too heavy for the undamaged lower structure? And heavy enough to cause global collapse with no resistance? This is impossible, prove me wrong with a precedence.

Originally posted by ANOK

Originally posted by Achorwrath
South Tower - Upper Floors toppeld to the left before falling down on top of the rest of the building

And how do you explain how this happened? You obviously haven't looked into to hard.

The top of WTC 2 was experiencing 'angular momentum' when it was tilting.

The angular momentum of an isolated system remains constant in both magnitude and direction. The angular momentum is defined as the product of the moment of inertia I and the angular velocity. The angular momentum is a vector quantity and the vector sum of the angular momenta of the parts of an isolated system is constant. This puts a strong constraint on the types of rotational motions which can occur in an isolated system. If one part of the system is given an angular momentum in a given direction, then some other part or parts of the system must simultaneously be given exactly the same angular momentum in the opposite direction. As far as we can tell, conservation of angular momentum is an absolute symmetry of nature. That is, we do not know of anything in nature that violates it.

Read that and understand it. Then explain how the angular momentum of the top changed to vertical momentum. How can the top, when in angular momentum, it's force is not in the vertical plane, suddenly decide to go straight down? The only way that could have happened is if the bottom, independently collapsed from under the top. In fact you can see this if you look at the vid real close, the top suddenly has no pivot point for it's tilt, so it has no choice but to drop following the collapsing bottom section of the building.

Falling bodies will always follow the path of least resistance, that's why the top tilted in the first place, if it had the energy to collapse the building under it it would have done that immediately, not while undergoing angular momentum.

Also the building had held the top since it was built, how did it suddenly get too heavy for the undamaged lower structure? And heavy enough to cause global collapse with no resistance? This is impossible, prove me wrong with a precedence.

you see what you want and of course since you only see what you want you find what you are looking for.

Your principal works on unsupported unrestrained bodies in motion.
Now apply that an object that is connected to another mass.

Watch the video setps. You see the building tilt but NOT fall over

If you take and bend an aluminum can does it fold into a 90 degree angle?

No as the can bends over the front part folds in. does it snap off? no again the forces acting on the front and back prevent this. the back folds over and the front folds in on itself.

you can even do this with corrogated card board and see the effect. The outside does not simply snap over.

The back of the top floors did not snap free either it folded over like a beer can and continued down.

As with all comments like "the building had held the top since it was built"

They are flawed in that the building was not on fire AND structually damaged since it was built.

You might as well have said, I do not see how the bullet killed him, he was alive for 30 years before that?

Ok show me another steel building hit by a palne and on fire for comparison and I will show you how they match

We are not talking about precident, you have to look at the physical evidence not make assumptions based on other situations that are not like this one, if there was a precident we all would know what happens when you colide a jet with a steel building and it looses strutural integrity and catches on fire.

The building fell in on itself as workers were pouring the concrete for the roof to complete the framework. There were electricians, plumbers, and bricklayers on the floors below.

Brevard County authorities said that it would be a month before the cause of the collapse could be determined with certainty. Several state and Federal agencies, including the Labor Department, sent investigators to the site.

Some workers were critical today of the speed with which the building was being constructed. The landscape of sand and palms is dotted with new condominiums of similar design completed to take advantage of the needs of the revived Cape Canaveral space center and its associated aerospace companies. Speculation on Cause of Collapse

No controlled demo the upper floor gave way during the cocrete pour and it fell down on top of itself. and this was just a 5 story building nothing like the WTC's two towers.

Link

These are durring construction but note all fell due to loss of structural integrity.

WTC 1, 2, & 7 were all damaged WTC 1& 2 obviously so, WTC7 the damage went unoticed until it fell.

[edit on 18-3-2009 by Achorwrath]

[edit on 18-3-2009 by Achorwrath]

reply to post by Achorwrath


If you haven't already, check out a documentary called "9/11 Eyewitness". You can hear a series of detonations in the north tower just before collapse. As the detonations are going off, you can see the smoke in the impact zone being disturbed. Then collapse ensues with the audible detonations bringing down the building. Very clear controlled demolition.

There are also a series of audible detonations in the south tower before collapse, but the south tower isn't visible from the vantage point of the video.

I'm currently working on a project that will hopefully dispel the skepticism and prove once and for all that the WTC was brought down with explosives.

reply to post by _BoneZ_

The sounds and debris coming out the sides were from compression m8,

Clap your hands together, there is compression, wind coming out the sides

reply to post by Seany


Firstly, the video I speak of is filmed from about 2 miles away. The sounds heard in the video are the deep booms from the explosives.

Secondly, if you're talking about the jets of dust/smoke coming out the sides as the buildings collapse, those are the direct result of explosives and had you done any research on controlled demolitions, you would know this:

See the jets of dust/smoke coming out the sides of these apartment towers?

[atsimg]http://files.abovetopsecret.com/images/member/82681924bc62.jpg[/atsimg]

Explosives, not compression.

Oh by the way, if you clap your hands together or even drop a book on a dusty floor, the air that is moved comes out all 4 sides and across the whole length of each of the 4 sides. Not from a localized spot as explosives do.

Lastly, many of the jets of dust/smoke at the WTC were 20-50 or more floors below the collapse. The building wasn't even collapsing where some of these jets of dust were. The high-powered explosives that create these jets are used to weaken the hardest part of the building. These jets are high-powered explosives weaking the structure as the structure is collapsing.

Please do some research on controlled demolitions before you post such things, thanks.

Originally posted by _BoneZ_
reply to post by Achorwrath

 

If you haven't already, check out a documentary called "9/11 Eyewitness". You can hear a series of detonations in the north tower just before collapse. As the detonations are going off, you can see the smoke in the impact zone being disturbed. Then collapse ensues with the audible detonations bringing down the building. Very clear controlled demolition.

There are also a series of audible detonations in the south tower before collapse, but the south tower isn't visible from the vantage point of the video.

I'm currently working on a project that will hopefully dispel the skepticism and prove once and for all that the WTC was brought down with explosives.

The problem with that is that the sound of the floor collpasing onto each other would sound similar. remember they are breaking and each is slamming into the other.

Also the two main towers were built in sections of 4 floors (at least that is the way the original blue prints read.

when they failed what would the sound be like?

I used demolitions for over 9 years on a regular basis and it is not a lound crack or bang but a lower whump like sound of the displaced air.

People reported hearing what sounded like explosions, but how do we know that what they heard was a real detonation or what they have been conidtioned to from TV and Movies?

As I have said before I wached a 6 inch nylon line let go and it sounded like a gun shot.

Enough that the MPs and SPs at the base responded to it.

I have not seen 911/eyewitness but will watch it once I find it and let you know what I hear.

remember there are no columns supporting the floors. just the inner core and the outer wall.

We know that there was structural damage to multiple floors on both towers.

I do not think the trusses failed as NIST claims but I do think that the bolts holding the trusses to the outer supports failed.

MY reason for this is a combination of shock, impact stress, and fire.

if you lost support along an entire axis the floor would drop like an umbreall on that side. one it reached critical stress it would have sheared from the central core.

[edit on 18-3-2009 by Achorwrath]

Originally posted by Achorwrath

The problem with that is that the sound of the floor collpasing onto each other would sound similar. remember they are breaking and each is slamming into the other.

Great points as usual Achorwrath.... I try to post this following video every once and a while to give an example as to what metal sound like when it collapses.

Originally posted by _BoneZ_


Please do some research on controlled demolitions before you post such things, thanks.

8 years in mining , I loaded my own faces ,benches and pilot holes and slashes

Used Tovex, Amex, bee line electric caps and blasting caps with bee line


Your qualifications with explosives ....................................

I dont need Re search......... I have Real life

[edit on 18-3-2009 by Seany]

Originally posted by Achorwrath
The problem with that is that the sound of the floor collpasing onto each other would sound similar. remember they are breaking and each is slamming into the other.

As I said in my other post, the video is filmed from 2 miles away. You're not going to hear any of the actual building collapses. You only hear the deep rumbling and booms from the explosions.

Secondly, the buildings collapsed in a little over 10 seconds. That's 10 floors per second. You won't hear a loud boom with 10 floors hitting each other every second, sorry. But you will hear a loud boom from a detonation every 10 floors to take away the resistance below the collapsing floors.

By the way, the initial detonations in the north tower are not coming from the floors collapsing as the building hadn't started collapsing yet. The detonations are the initiation to collapse.

As I said, as the last of the detonations are going off, the smoke is disturbed, then the building starts to collapse.

Unless you buy the DVD version, the online versions have problems with sound syncing. But in the project I'm working on, I took into consideration the speed of sound and got the collapse and the detonations as close together as I could.

Originally posted by Achorwrath
I used demolitions for over 9 years on a regular basis and it is not a lound crack or bang but a lower whump like sound of the displaced air.

I did say in my post that the detonations are very low booms. You'll see once you watch it.

Here's the video by the way. Pt. 1 of 3:

video.google.com...

You should be able to see the other 2 parts there as well.


[edit on 18-3-2009 by _BoneZ_]

reply to post by Seany


You can name off any type of explosive you want, but don't sit there and dismiss the jets of dust/smoke at the WTC because you don't want to believe that 9/11 was an inside job.

Those jets are seen in most controlled demolitons and are from explosives. The WTC buildings also fell like demolitions and at the speed of demolitions. No steel-structured high-rise has ever collapsed in history due to fires, nor in the manner or speed that the WTC did.

The buildings fell at near free-fall speed like in demolitions, had jets of dust/smoke from explosives like in demolitions.

If it walks like a dog and barks like a dog...

reply to post by _BoneZ_


Dont challenge people on their qualifications , if you dont know them yourself


Doesn't help your arguement at all

reply to post by Seany


Sorry, but you were the one trying to dismiss the jets of dust/smoke at the WTC because you don't want to believe that 9/11 was an inside job, yet every other aspect of the WTC's collapse is exactly indicative of controlled demolitions, up to AND INCLUDING the jets of dust/smoke caused by the high-powered explosives used to bring buildings down.

When I mentioned do some research, I meant on the jets of dust/smoke. I've done extensive research on these jets of dust/smoke. If anyone else had done research on controlled demolitions and specifically on the jets, they wouldn't doubt that the jets at the WTC were caused by explosives, period.

Originally posted by _BoneZ_
reply to post by Seany

 

You can name off any type of explosive you want, but don't sit there and dismiss the jets of dust/smoke at the WTC because you don't want to believe that 9/11 was an inside job.

Those jets are seen in most controlled demolitons and are from explosives. The WTC buildings also fell like demolitions and at the speed of demolitions. No steel-structured high-rise has ever collapsed in history due to fires, nor in the manner or speed that the WTC did.

The buildings fell at near free-fall speed like in demolitions, had jets of dust/smoke from explosives like in demolitions.

If it walks like a dog and barks like a dog...

You are right,
no high rise has fallen from fire;

The WTC towers fell from a combination of shcok, impact stress, structural damage AND fire.

The problem with most people is they forget the other factors.

everyone wants to conentrate on one aspect; Fire.

It was not the fire alone.



[edit on 19-3-2009 by Achorwrath]

Ok I watched the videos last night,

The quality from the google source was terrible.

There were many times where I heard nothing at all but the words would pop up on the screen saying things like; did you hear that?

Then would point to a cloud of something that could be either dust or smoke.

later the booms I heard (again due to quality it was almost impossible to ID) sounded like more like metal and or concrete giving way than explosions.

Direction due to stereo sound (non posistional) was impossible to determine.

they draw your attention to what they heard but as for using that as evidence? I am not so sure. Again there is no possibility to determine direction from the poor quality stereo sounds.

If you are already inclined to believe it was demo then yes that is what you will hear if not then you will more than likely hear something else.

Again it all boils down to quality. I am trying to find a source that I can throw on my NLE (non-linear editing is a hobby of mine and I am not claiming to be an expert at it) system to see if I can ID pulses in the sound wave to cooborate some of the video.

I will let you know what I find if I am able to find a good enough copy.

I will say it is interesting but certainly not conclusive.


[edit on 19-3-2009 by Achorwrath]

[edit on 19-3-2009 by Achorwrath]

Originally posted by Griff
reply to post by CameronFox

 

You're on the right track Cameron but have the principle mixed up.

What is happening with the pumpkin is that it is hitting the door with force and in turn causes the hinges of the door to fail.

Notice that the door does not end up with a cartoon cut-out of the pumpkin in Looney Tunes fashion? But rather just gets pushed out the other side?

blah blah

To Cameron Fox, What if that van was made of structural steel with a few inches thickness each side? Wouldn't that make your pumpkin comparison a little more fair?



The pumpkin would go splat against a steel column. Your example is a very bad comparison.



Go shoot your pumpkin at one of those ^

Griff you can see from the official graphical records and analysis steel beams were indeed cut by what should be soft elements, not just at the welds or bolts failed (although some clearly did too).





[edit on 19-3-2009 by Insolubrious]

reply to post by CameronFox


omg Cameron is hugging the big blue crane. Apples and oranges again.



[edit on 19-3-2009 by Insolubrious]

Originally posted by Insolubrious
reply to post by CameronFox

 

omg Cameron is hugging the big blue crane. Apples and oranges again.

[edit on 19-3-2009 by Insolubrious]

How is the sound of breaking Steel from the crane different from the sound of breaking Steel in the WTC towers?

The shots that have been posted of Controlled demo are on reinforced Concrete supported structures, does that make them invalid also as they are "Apples and oranges" ?

If it does then I guess we can thorw out Anok's picutre of the controled demo example right? After all we know concrete and steel act differently?

And the picture that Bonez posted, as that is also a reinforced concrete structure.

A video demonstrating the sounds (low booms) made by a failing steel structure (remember the WTC were made of steel) is relavent and a good comparrison.

You cannot have selective evidence; otherwise your conclusions are not valid.



[edit on 19-3-2009 by Achorwrath]

Big blue crane collapsed in one direction and didn't break up into little pieces! That is how the twin towers SHOULD of fallen, like big blue crane - falling over in one large piece following the path of least resistance but hey guess what, the twin tower buildings fell into their own footprint in a massive cloud of powder, which consisted of concrete AND steel. They didn't just fall over, every floor was blown into smithereens!

Originally posted by Insolubrious
Big blue crane collapsed in one direction and didn't break up into little pieces! That is how the twin towers SHOULD of fallen, like big blue crane - falling over in one large piece following the path of least resistance but hey guess what, the twin tower buildings fell into their own footprint in a massive cloud of powder, which consisted of concrete AND steel. They didn't just fall over, every floor was blown into smithereens!

Ok, you are making an assumption here;

You are assuming that the weight above the structural damage would not affect the lower portions of the building.

Here is the math

According to the blue prints (I have linked them before) the building was designed in groups of four floors.

Now each floor would have to AT LEAST support the wieght of the floor above. but lest say it can support 4 making this support X using Griff's FoS of 2.5 we have each floor supporting 2.5X.

North tower, floor 93 lost 15-16 supporting colms (according to photographs) this means that that floor alone lost 25% of its outer support. None of the trusses along that portion were suppoting the floor anymore. this is without even touching the possibility that central core beams were afected.

So floor 93 is now (2.5X)*.75= 1.875X

We know from photogrpahs and witness accounts that there was similar damage to the floors from 94-98.

So each one in turn was reduced to s similar factor.

Lets heat up the metal bolts now according to posts here by Griff, the metal reached at least 250c
so lets give it a 10% reduction in strength although it is probably more like 15%

1.875X*.9 = 1.6875X

now above floor 93 you have 17 floors 17 / 4 = 4.25X This is the weight shown as a factor of support.

1.6875X < 4.25X

Simplified yes. but still showing a grealy increased structural demand.

Now since the fires were mainly on the oposite side of the impact hole, we now see a weakening happeing on the other side of the tower. where the fires are working on the supporting bolts (those have a higer likely hood of failure) they used bolts as they would be able to deal with the constant lateral movement by the outerwalls (welds can fracture easier).

This means there would have been a unifom loss of support across the affected floors, remember the building is not a solid mass. it is made up of individual pieces each which have their own failure rate.

The South tower actually had more floors above the point of impact to deal with (77-85)

[edit on 19-3-2009 by Achorwrath]

[edit on 19-3-2009 by Achorwrath]