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# structural engineer leslie robertson interview

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posted on Mar, 20 2009 @ 09:42 AM

Originally posted by Achorwrath
Hang on - you have been preaching an FoS of 2.5 for quite a while and now you pull 6 out of the air?

All members of the building will have a different FoS. So, in essence there could be millions of FoS for the towers.

2.5 is just a minimum we usually use. Not what the towers actually had. I've read it was much more than 2.5 for most members.

6 is the maximum load not the FoS
if the maximum load is 6 you apply the FoS on top of that

So, you want to state that with a maximum load of 6 and a FoS of 2.5, the floors could actually hold 6 x 2.5 = 15 times their own weight?

Sure starts to make your analysis fall apart then eh? (pun intended).

As far as the damage to the core of WTC 2, I'm not the one who states it was barely hit. That's observable. And I have no idea why you posted anything about the facade damage when we were talking about the core.

You jump around so much it's hard to have a conversation with you.

[edit on 3/20/2009 by Griff]

posted on Mar, 20 2009 @ 09:58 AM
I cover all evidence in the event.

Interior damage, external damage, Joints (bolts and welds)
FoS is the factor used above the expected maximum load that you paln for a structure.

you are stating that the building would have stood, I am showing evidence as to why I would not have.

This will need to cover damage across multiple sides, floors, columns of the structure:

but hey if you want to take away the 2.5 and go with 6 then here

X = the amount of wieght each floor could support undamamgaed using griff's 6)

X *.75 = .75X

You would then take the multiple floors above and group them into the support factor (6) so 17/ 6 = 2.833333

Exterior damage on the impact side of north tower -

Up to 25% loss of lateral and external support for the structure on eight floors.

Exterior Damage on the oposite side from imapct north tower -

Visible fascade and structural damage to supporting columns on at least 3 floors.

Interal Damage to floors and floor trusses North Tower -

reported damage to floors, (missing concrete, buckled trusses)

Reported damage to core (blocked stairwells damage to exposed colums in the core)

Fire-Massive uncontrolled fires on multiple floors (as far up as 102 and as far down as 24)

Concnetrated on Floors 94-96
Most fires burning oposite from the point of impact.

Was that more linear for you?

I would not have expected a personal attack from you.

posted on Mar, 20 2009 @ 10:31 AM
It goes like this:

You have a dead load (D.....the weight of the members) and you have a live load (L...the weight of the people, desks, computers, fax machines etc.)

Now you add these calculated loads (sometimes with a factor greater than 1 to add a little more FoS):

(D + L)......this is the allowable load the floor has to be designed to hold

Now, on the other end of the equation we have .85 x the ultimate strength of the member (or 85% of the members strength.....i.e. if using A-36 steel = 0.85*36,000 psi) to be used to support the loads above so that

D + L < .85U

This, as stated previously, gives an ingrained factor of safety since we use only 85% of the strength.

This is the allowable strength of the member (remember it has a FoS ingrained into it).

Now to get the design strength of the member, we take the allowable strength and divide it by a FoS (usually 2.5-3).

So, now our equation becomes D + L < .85U/2.5

But, in the case of the towers, NIST found that the total FoS for the floors was 6.

Meaning that the ingrained FoS into the allowable strength plus the FoS they used to obtain the design strength equaled 6.

Does that explain it any better?

[edit on 3/20/2009 by Griff]

[edit on 3/20/2009 by Griff]

posted on Mar, 20 2009 @ 11:26 AM

The perimeter structure was constructed with extensive use of prefabricated modular pieces, which consisted of three columns, three stories tall, connected by spandrel plates. The perimeter columns had a square cross section, 14 inches (36 cm) on a side, and were constructed of welded steel plate.[48] The thickness of the plates and grade of structural steel varied over the height of the tower, ranging from 36,000 to 100,000 pounds per square inch[49] (260 to 670 MPa). The strength of the steel and thickness of the steel plates decreased with height because they were required to support lesser amounts of building mass on higher floors.[48] The tube-frame design required 40 percent less structural steel than conventional building designs.[50] From the 7th floor to the ground level, and down to the foundation, the columns were spaced 10 feet (3 m) apart.[51] All columns were placed on bedrock, which, unlike that in Midtown Manhattan, where the bedrock is shallow, is at 65–85 feet (20–26 m) below the surface.[52]

Source

36,000 Psi intact like you said but you are completely forgetting weakend the support for loss of columns AND floor trusses.

You are still overlooking the eseential point. The total structure FoS is meant for an intact floor.

this means - No damage to supporting outer columns, No Damage to the Floor or trusses (remember they are there to support and stiffen the walls for lateral sway and to a lesser extent provide support for floors above through bracing), No damage to central core columns.

You cannot take a static number and apply it to a structurally altered building.

The dynamics of the building are changed, the building is no longer as designed.

Until you include that in your investigation you are leaving out a huge piece of the puzzle.

I said from the start that was an Over simplification of the process.

It was intended to show how cumulative damage to the floors, outer colums and inner core contributed to the collapse.

Also it is not very scientific to discard parts of a report and pick the ones you like;

I found that NIST completely overlooked the joints (Bolts, Welds etc) in their report; this means that all conclusions are not valid. Hence I discard the whole report.

posted on Mar, 20 2009 @ 11:44 AM

Originally posted by Achorwrath
I found that NIST completely overlooked the joints (Bolts, Welds etc) in their report; this means that all conclusions are not valid. Hence I discard the whole report.

posted on Mar, 20 2009 @ 12:32 PM

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!

If youACTUALLY look at the videos of the collapse of the towers you see that the floors of the towers ABOVE the impact area fall as one mass.
So the massive loads of remember 1500 tons per floor and in the case of the south tower thats about 44,000 tons DROPPED you see it on the video, so even if as someone stated the floors could cope with a load of 4-6 times normal load they could not cope with the loads they were subjected to.
You even see it topple slightly to one side BECAUSE of the area of damage done by the aircraft.
Re planes flying through the steelwork you see example of things like this all the time Martial Artists hands through,timber ,bricks even ice,the pumpkin gun soft object hits a harder object but due to the energy involved it causes damage.
Its funny but the planes get called flying beer cans when thay hit the towers but when one hit the Pentagon a building DESIGNED to resist attack people complain that little is left of the plane!

The other thing re videos of buildings being demolished apart from being mostly concrete in the videos they will have had MANY structural elements removed they also start explosives on lower floors and go up the way ,towers fell from top down,the towers did not fall in their own footprint either

When structural elements fail such as bolts, steel even concrete you can get a noise that sounds like an explosion.
did none of the explosives go off when the planes hit/started fires etc.

posted on Mar, 20 2009 @ 02:14 PM

Originally posted by wmd_2008
So the massive loads of remember 1500 tons per floor and in the case of the south tower thats about 44,000 tons DROPPED you see it on the video,

Interesting. How does the upper portion just drop when columns buckle at failure and not shear?

Where does this "drop" come from?

The other thing re videos of buildings being demolished apart from being mostly concrete in the videos they will have had MANY structural elements removed

And why would they do this if gravity can only cause a demolition to go straight down? That's why we hear why the towers didn't topple right?

When structural elements fail such as bolts, steel even concrete you can get a noise that sounds like an explosion.

Plastic deformation happens in steel. It doesn't just suddenly fail with explosion sounds.

Or did you mean when they impact other members?

did none of the explosives go off when the planes hit/started fires etc.

C-4 can be thrown into the fire and not explode, just burn. No, I'm not saying C-4 was used, I'm just giving an example of an explosive that doesn't explode in fire.

Actually, the soldiers in Vietnam used to burn C-4 to keep warm.

posted on Mar, 20 2009 @ 02:28 PM

C-4, properly known as composition 4, is a plastic explosive developed in the 1960s as an improvement to a pre-existing plastic explosive called Nobel 808. C-4 is a combination of explosive, a plastic binding agent, a plasticizer, and a marking chemical added to ease detection.

Like all plastic explosives, C-4 is extremely stable. Called an insensitive explosive, C-4 is very difficult to trigger by accident. Impact and fire are separately not enough to detonate C-4, but the combination of the two can create the necessary circumstances for detonation, however, fire will cause C-4 to burn with very high heat, even underwater, and was often used by US troops in Vietnam to cook food. C-4 is 1.34 times more explosive than TNT.

source

C-4 under heat (fire) and pressure explode.

I know you are not saying it was used, just pointing out that C-4 would have more than likely exploded under those conditions.

The reson is that the burning material is the binder compound, as it goes you are left with the unstable explosive chemicals (two major parts)

Plastic Explosives were and still are carried due to their stability. other explosives used in Demo are less stable than C-4

Remeber the steel in the columns (outer) was bolted, what sound do you think the botls would make when they broke?

there were whole sections of outer column in the rubble with the blots sheared completely off.

[edit on 20-3-2009 by Achorwrath]

posted on Mar, 20 2009 @ 02:46 PM

Originally posted by Griff

Originally posted by Achorwrath
I found that NIST completely overlooked the joints (Bolts, Welds etc) in their report; this means that all conclusions are not valid. Hence I discard the whole report.

Originally when looking at the evidence I felt that structural failure due to damage, shock and fire caused the collapse.

I felt the welds holding the floor trusses parted due to shock and that fire assisted by weakening the structure already damamged by impact.

However, thanks to Bonez (who popped up the pictures of the columns and spandrels)

I realize that I had forgotten that the trusses were only channel welded at the cores and bolted to the outside.

This made the structural failure more likely with the given events

Bolts shear under impact stress. ( a lesson learned from Titanic and other ships) I began to ask myself how much real shock damage would there have been on the bolts and channel welds?

So I started looking at all sides of the towers for indicative damage (shear and spandrel separation) I found it on almost all sides.

Next I checked the information that I had before on the condition of the core columns and again found reports of the core columns being damaged (bent, kinked, and some reported them as cut although they were probably broken.)

from there I estimated what effect fire would have on the damaged portion and found that it would more than likely have precipitated the upper collapse.

Once the upper weight fell down the design of the towers only helped it.
Just like the condo collapses I posted about.

Unrestrained weight of that type would not be stopped by the reaming structure.

I also looked at debris patterns. much of the lower outside columns were pushed out away from the building inconsistent with controlled demo - so I had dismissed that a long time ago.

posted on Mar, 20 2009 @ 04:38 PM

Originally posted by wmd_2008
when one hit the Pentagon a building DESIGNED to resist attack people complain that little is left of the plane!

The WTC towers were also designed to withstand the impacts of planes. Further, it doesn't matter if a jetliner hit the Pentagon, jello, Smokey the Bear or a tree, there will still be 300,000 pounds of aircraft debris at the scene. Planes do not disintegrate, disappear, burn up or vaporize. Witnesses inside the Pentagon and outside said there were no signs of a plane, or too few parts to account for a large jetliner. These are undisputed facts.

Originally posted by wmd_2008
they also start explosives on lower floors and go up the way

They did start the explosives in the lower levels of the WTC first. Did you not see the Naudet Brothers' 9/11 video where they showed the lobby of the WTC completely destroyed from the explosives in the lower levels that many witness described? The movie also shows the parking garages down in the lower levels that were destroyed. Many witnesses heard and felt these explosions and many people either died or were severely injured from these explosions.

No two controlled demolitions are the same.

Originally posted by wmd_2008
towers fell from top down

Many controlled demolitions start at the top and go down. For instance these apartment towers were detonated from the top down just like the WTC:

Originally posted by wmd_2008
if they had explosive already planted why did none of the explosives go off when the planes hit/started fires etc.

There are over 1000 different types of explosives that can be used in controlled demolitions that we know of. There are many types of explosives where fire or water will not damage them. Many explosives take chemical reactions to ignite them, not just fire.

posted on Mar, 20 2009 @ 06:14 PM

Originally posted by wmd_2008
Re planes flying through the steelwork you see example of things like this all the time Martial Artists hands through,timber ,bricks even ice,the pumpkin gun soft object hits a harder object but due to the energy involved it causes damage.
Its funny but the planes get called flying beer cans when thay hit the towers but when one hit the Pentagon a building DESIGNED to resist attack people complain that little is left of the plane!

yeah lol what idiots...

You see bro you have to understand physics and how to apply it to different situations. A guy chopping wood with his hand is not the same as aluminum hitting steel.

The bones in your hand have more mass than wood, bricks, or ice. It is hard to do but sry it doesn't fit planes hitting buildings.

As far as the pentagoon goes... Newton says that when objects collide the force on each object is equal, except the deceleration, or bounce back which is relative to it's mass. So, when an object hits another object the object with the least mass receives the most damage.

I'm sure you've seen the F-4 hitting the concrete vid? That is a perfect example, plane is destroyed concrete is not, more mass in the concrete. If the plane had the more mass it would have gone through the concrete. So, seeing as they plane went through that reinforced wall at the pentagon, it could not have also been destroyed by going through that wall. Also there was nothing else past that wall that would have destroyed the plane. That leaves just the fire. Where is the plane?

posted on Mar, 20 2009 @ 06:52 PM

Originally posted by Achorwrath
from there I estimated what effect fire would have on the damaged portion and found that it would more than likely have precipitated the upper collapse.

This is the part I'm interested in. How did the fire precipitate the collapse? What happened? Did the columns lose their unbraced length and buckle? Etc.

NIST believes that the floor trusses sagged and pulled the exterior columns inward causing a P-delta effect that exceeded the strength.

posted on Mar, 20 2009 @ 07:21 PM

Originally posted by Griff

And I'll state this again. ALL 9/11 video footage I have seen has been without audio because I can't even hear the collapses (you know, those loud booms you claim are steel impacting steel).

WTC-7 with Audio.. (no explosions)

Tower Collapse -with audio

[edit on 20-3-2009 by CameronFox]

posted on Mar, 20 2009 @ 07:57 PM

Originally posted by Griff

Originally posted by Achorwrath
from there I estimated what effect fire would have on the damaged portion and found that it would more than likely have precipitated the upper collapse.

This is the part I'm interested in. How did the fire precipitate the collapse? What happened? Did the columns lose their unbraced length and buckle? Etc.

NIST believes that the floor trusses sagged and pulled the exterior columns inward causing a P-delta effect that exceeded the strength.

The bolts and vibration dampeners. along the outer wall.

They are actually a simpler solution to the equation. they would have a lower tolorance for heat, shear, and shock damage.

remember that with the type of truss the WTC had for flooring the main support for gravity is from the bottom.

That part of the truss was only connected via a vibration dampening system to the spandrels. The upper portion appears (the reproduction of the blue prints is terrible) to be single bolt (although it could be two.) connected to a welded eye on the spandrel.

how much damage from imapct shock and fire could they take before failing?

how many would it take to shear or break before the floor tried to sag?
pulling more bolts away and pulling some of the remaining columns in with them.

posted on Mar, 20 2009 @ 11:45 PM

In North Tower plane hit building dead center - a lot of the fuel (there was
over 9000 gallons in total) was dumped into the stairwells and elevator
shafts. The fuel ran down the express elevator shafts which serviced
WINDOWS ON THE WORLD resturant on the 106-107 floors. The fuel
ignited and caused a fireball which blew down to the basement levels
and blasted out the elevator shafts on the ground floor. It was this
scene the Naudets recorded entering the building - there were
numerous people seriously burned in the lobby.

Here is page from "102 minutes" - Captain Anthony Whitaker of Port
Authority Police who witnessed fireball.

People coming out of the buildings half burned, the fuel must have spewed down and hit some people. A lot of burns literally down through the skin to the bone. I had two patients on my ambulance, vehicle 111. FBI Agents were telling us to move our vehicle from the corner of Vessey and West, cause there was debris from the airplane which they needed for evidence. I guess it was NTSB, they wanted the area secured. There was nowhere for us to move the vehicle, cause there was debris everywhere. FDNY EMT Alwish Monchery

or this

Erik O. Ronningen: The main lobby was a shambles. Chandeliers down; the marble walls in broken piles on the floor; the giant directional signage dangling from the ceilings; all the windows broken, the revolving doors broken and off kilter and the elevator doors all blown out. We walked through water pouring out of the ceiling like Niagara Falls, and sloshed through the darkened Mall in shin-deep water. www.bigmedicine.ca...

Firefighter John Morabito of ladder 10, which is just 200 yards from the north tower.
“Just inside the front entrance, Morabito found two victims of the fireball. A man, already dead, was pushed against a wall, his clothes gone, his eyeglasses blackened, his tongue lying on the floor next to him. The other was a woman, with no clothes, her hair burned off, her eyes sealed.

“The woman, she sat up. I’m yelling to her, ‘Don’t worry, we’re going to help you,’” Morabito said. “She sat up and was trying to talk, but her throat had closed up. She died right there.” www.fdnytenhouse.com...

Mercedes Rivera: I saw a burned woman in a sitting position in the lobby, as if she was still typing behind a desk.... She was already dead.” Susan Hagen and Mary Carouba. Women at Ground Zero: Stories of Courage and Compassion. Indianapolis: Alpha Books, 2002. P. 22

Can read more accounts of the fireballs which emerged from elevator shaft

Note - smell of kerosene/jet fuel as described by many.

What you have here is a fuel vapor/air explosion or more correctly a
deflagation (rapid burning)

posted on Mar, 20 2009 @ 11:46 PM

posted on Mar, 21 2009 @ 07:42 AM

You probably shouldn't post such things without first doing research on the topic you're posting about. It really would make you look more credible.

First and foremost, the ignition of fuel is NOT an explosive. This isn't Hollywood. Do you understand how powerful the explosives would have to be to destroy the lobby blowing out all of the glass, breaking up the marble fixtures on the walls? Destroying the entire parking garage in the basement levels? Have you even seen the pictures of the destruction of the parking garage?

Almost all of the jet fuel burned up in the initial fireball when the planes impacted. What do you think that huge fireball was?

"Myth Busters" already did a segment on such things and found fuel CANNOT explode like it does in the movies. The movies use nitroglycerin to make fuel tanks on cars and other things explode.

There are many witness accounts of the lower level explosions, but construction worker Phillip Morelli has one of the most detailed accounts:

I go downstairs to sub-basement 4, the foreman tells me to remove the containers. As I'm walking by the main freight car of the building in the corridor, that's when I got blown. I mean the impact of the explosion of whatever happened threw me to the floor and that's when everything started happening.

I was racing, I was going towards the bathroom, I opened the door and all of a sudden a big explosion happened again and all of the ceiling tile was falling down. Light fixtures were falling, swinging out of the ceiling. And I come running out the (bathroom) door and everything, the walls were down. Then I started running towards the parking garages.

There was alot of smoke down there, there was alot of people screaming. People came with us as we were running up the ramps. You have to go clear across the underground tunnel from the north tower to the south tower because that's the way you gotta run. And then all of a sudden, it happened all over again. Another explosion pushed us to the floor. Right in the basement you felt it. Walls were caving in.

I know people that got killed in the basement. I know people that got broken legs in the basement. I know people who got reconstructive surgery from the walls in the basement hitting them in the face.

Now let's take a look at the damage. (these are screen caps from video, so not the best quality)

Lobby glass and marble fixtures destroyed:

Notice the elevator on the very right side of the second picture? Notice there are no fires, no scorch marks or any evidence of jet fuel burning anywhere. This is all explosive damage only. Let's continue.

Parking garage completely destroyed:

This damage is cause by high explosives used to weaken the foundation of the WTC towers like seen in most every other controlled demolition.

So, you debunkers can stop with the "jet fuel fireball destroyed the lower levels". Every floor between impact zone and the basement would have been blown if that was the case. A magical jet fuel fireball isn't going to pick a certain floor to stop on. Oh and fire rises, not travells a quarter mile down the tower and then stops at certain floors.

You are certainly welcome to make things up and tell yourself anything you need to, to help you sleep better at night and to continue to deny the truth. But the physical evidence, video evidence and witness testimony all speak for themselves.

posted on Mar, 21 2009 @ 09:16 AM

Originally posted by _BoneZ_

You probably shouldn't post such things without first doing research on the topic you're posting about. It really would make you look more credible.

I might suggest you do the same Bonez.

Originally posted by _BoneZ_ Do you understand how powerful the explosives would have to be to destroy the lobby blowing out all of the glass, breaking up the marble fixtures on the walls?

The lobby marble is installed with an adhesive (as can be seen in the pictures you posted. Can you please point out the combustible materials in the elevator foyer?

Regarding the elevator doors:

"It was quite hectic, and we did what we could to stay in contact with the elevator passengers while helping to direct other people out of the building and direct firemen to the stairs and the elevators," Bobbitt remarked. "When entering the North Tower, we saw the marble on the walls was severely cracked, and Riccardelli told everyone to stay back from the walls. Don (Parente) noticed that the doors of elevators number 6 and 7 had been blown out."

–Courage Above and Beyond the Call of Duty: A Report of the September 11, 2001 Experiences of Port Authority Engineers at the World Trade Center

Victims in the Lobby:

-" I saw a burned woman in a sitting position in the lobby, as if she was still typing behind a desk.... She was already dead.”
-Mercedes Rivera

Just inside the front entrance, Morabito found two victims of the fireball. A man, already dead, was pushed against a wall, his clothes gone, his eyeglasses blackened, his tongue lying on the floor next to him. The other was a woman, with no clothes, her hair burned off, her eyes sealed.-Firefighter John Morabito

Originally posted by _BoneZ_ Destroying the entire parking garage in the basement levels? Have you even seen the pictures of the destruction of the parking garage?

Originally posted by _BoneZ_

Almost all of the jet fuel burned up in the initial fireball when the planes impacted. What do you think that huge fireball was?

As I am sure your research has show you, the NIST report states that less than 15% of the fuel burned in the spray inside the building. Pretty close to the same amount was with the fireball outside the building. That leaves well over 1/2 the fuel still inside the building.

2.4

posted on Mar, 21 2009 @ 10:00 AM
Bonez
The military uses FAE (fuel air explosives) all the time.
Especially in urban areas due toi fragmentation of glass etc. it is an amazing anit-personnel weapon.

This is one of the reasons those flights were chosen they had more fuel in them that shorter flights

posted on Mar, 21 2009 @ 10:07 AM

Originally posted by Griff

Originally posted by wmd_2008
So the massive loads of remember 1500 tons per floor and in the case of the south tower thats about 44,000 tons DROPPED you see it on the video,

Interesting. How does the upper portion just drop when columns buckle at failure and not shear?

Where does this "drop" come from?

The other thing re videos of buildings being demolished apart from being mostly concrete in the videos they will have had MANY structural elements removed

And why would they do this if gravity can only cause a demolition to go straight down? That's why we hear why the towers didn't topple right?

When structural elements fail such as bolts, steel even concrete you can get a noise that sounds like an explosion.

Plastic deformation happens in steel. It doesn't just suddenly fail with explosion sounds.

Or did you mean when they impact other members?

did none of the explosives go off when the planes hit/started fires etc.

C-4 can be thrown into the fire and not explode, just burn. No, I'm not saying C-4 was used, I'm just giving an example of an explosive that doesn't explode in fire.

Actually, the soldiers in Vietnam used to burn C-4 to keep warm.

Are YOU actually looking at the videos YOU can see the part of the building drop above the impact point HENCE an extremely large DYNAMIC LOAD IS APPLIED TO FLOORS at and below the impact point!

When buildinga are demolished in a controlled way MANY structural elements are removed many internal walls etc a lot of the time external walls between concrete floors are removed as well.

Video link not the best example

You can see parts of building removed explosive charges from bottom.

When structural steel componets fail THEY can make loud bangs so imagine HUNDREDS FAILING in quick succession I know I have tested them on SITES to destruction!
It amazing the noise even a 12mm bolt can make when its pulled till failure ESPECIALLY we you are not used to seeing and hearing it.

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