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# structural engineer leslie robertson interview

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posted on Mar, 17 2009 @ 01:58 PM
reply to post by CameronFox

I think they would be correct. Once the plane starts to accordion into itself (within fractions of a second), it's mass becomes more than the steel and then can shear through it where it becomes greater and push it where it is not (but still greater than the bolts or welds).

So, really it's a combination of both in the tower's impact.

posted on Mar, 17 2009 @ 02:14 PM

Originally posted by Griff
Reply to Achorath:

Those numbers are the factors of the loads I believe.

There are several load factors but the main one is (going by memory here):

1.4L + 1.6D = phi x Ultimate strength.

That means that we design a member to hold 1.4 times the live load (a FoS of 1.4), 1.6 times the dead load (a FoS of 1.6), and phi is usually .8-.85 meaning 85% of the ultimate load.

When these are factored together, it gives a member that has a FoS above 2.5 that means the member can actually carry 2.5 times the load before it will fail.

If I'm wrong, please post the building code that says different from the 60's. Thanks.

Factor of safety (FoS) can mean either the fraction of structural capability over that required, or a multiplier applied to the maximum expected load (force, torque, bending moment or a combination) to which a component or assembly will be subjected. The two senses of the term are completely different in that the first is a measure of the reliability of a particular design, while the second is a requirement imposed by law, standard, specification, contract or custom. Careful engineers refer to the first sense as a factor of safety, or, to be explicit, a realized factor of safety, and the second sense as a design factor, but usage is inconsistent and confusing, so engineers need to be aware of both. The Factor of Safety is given to the engineer as a requirement. The Design Factor is calculated by the engineer.

Underlined by me for emphasis

Which method did the designers use? what was the FoS for the bolts that held the floor trusses in place? what type of steel were they? were they more subecjt to failure due to differences in composition?

Source

Also you might want to note that since the WTC was part of the Port Authority it did not have to comply with specific codes.

The WTC started construction in the 1970s. And the WTC towers built by the Port Authority of New York did not have to comply with the minimum requirements of the new1968 performance building code.

Source

What impact would a large section of floor missing have done to the structural integrity of the building? (remember witnesses repored a large section of the 96th floor missing, core colums that looked like they had been cut in half, and severed stairwells.)

I will search for the link again for the 60s FoS from the building codes, it was an online book but I do not remember the name. However, as a rmember it was .8 for concrete and 1.6 for steel buldings.

posted on Mar, 17 2009 @ 02:19 PM
reply to post by Griff

Here is another interesting abstract:

It was found that about 46% of the initial kinetic energy of the aircraft was used to damage columns. The minimum impact velocity of the aircraft to just penetrate the exterior columns would be 130 m/s. It was also found that a Boeing 767 traveling at top speed would not penetrate exterior columns of the WTC if the columns were thicker than 20 mm.

source:Impact of the Boeing 767 Aircraft into the World Trade Center. By: Karim, Mohammed R.; Fatt, Michelle S. Hoo. Journal of Engineering Mechanics, Oct2005, Vol. 131 Issue 10, p1066-1072.

posted on Mar, 17 2009 @ 02:34 PM

Originally posted by Achorwrath
I will search for the link again for the 60s FoS from the building codes, it was an online book but I do not remember the name. However, as a rmember it was .8 for concrete and 1.6 for steel buldings.

Maybe I'm just not an old school engineer, but .8 doesn't sound logical. Why would you design something that can only hold 80% of it's capacity before failure?

posted on Mar, 17 2009 @ 05:39 PM
reply to post by CameronFox

You can make those columns as thick as you want, the plane didn't penetrate the columns, the plane broke through the connectors that connected the columns.

posted on Mar, 17 2009 @ 05:57 PM

Originally posted by _BoneZ_
reply to post by CameronFox

You can make those columns as thick as you want, the plane didn't penetrate the columns, the plane broke through the connectors that connected the columns.

I almost agree with you, winesses reported colums cut in two.
Funny though now that I think on it, the biggest damage to a ship or sub is shock damage, (that is if it does not sink or explode from fuel or munitions getting hit) they end up with ruptured lines, welds rivets etc.

I wonder what the shock of imapct would have done to the bolts and welds connecting the trusses to the outer colums and inner core supports?

posted on Mar, 17 2009 @ 06:50 PM

Originally posted by Achorwrath
winesses reported colums cut in two.

I've never heard that in my years researching 9/11. I've only heard it from the no-planer disinfo cult. Suffice it to say that if you look at the higher-res images of the damaged area, you will see the columns are broke in sections of 3 as they were put together that way in 3's:

posted on Mar, 17 2009 @ 07:11 PM
reply to post by CameronFox

CameronFox, that airplane could have slammed through the whole building, taking out the entire core columns with it, but it would not have knock the WTC down. The floors and core columns below would have still stood. You all have to remember something else as well, the top part of the WTC that exploded away, vaporized in thin air, most of the debris exploded outward, in all directions there was no reason AT ALL for the rest of the WTC to have collapsed. The only reason it did come down is that they blew it up.

I cannot prove who blew up the WTC.
I cannot prove how they blew up the WTC.
I cannot prove what kind of explosives that where used.

So far, nothing else that has been presented in the government reports, does not stand up to creditable science, and is not accepted by most scholars in the academic word of science.

NIST is nothing but a political lie.

posted on Mar, 17 2009 @ 07:12 PM

Originally posted by _BoneZ_

Originally posted by Achorwrath
winesses reported colums cut in two.

I've never heard that in my years researching 9/11. I've only heard it from the no-planer disinfo cult. Suffice it to say that if you look at the higher-res images of the damaged area, you will see the columns are broke in sections of 3 as they were put together that way in 3's:

Then perhaps that is what they ment... I am only stating what I remember from my research after the event. if you look at the lower edge of the supporting colums it looks like they are bent over and or broken through.

That could account for people saying the colums were cut in half

posted on Mar, 17 2009 @ 07:19 PM

Originally posted by WonderwomanUSA
reply to post by CameronFox

CameronFox, that airplane could have slammed through the whole building, taking out the entire core columns with it, but it would not have knock the WTC down. The floors and core columns below would have still stood. You all have to remember something else as well, the top part of the WTC that exploded away, vaporized in thin air, most of the debris exploded outward, in all directions there was no reason AT ALL for the rest of the WTC to have collapsed. The only reason it did come down is that they blew it up.

I cannot prove who blew up the WTC.
I cannot prove how they blew up the WTC.
I cannot prove what kind of explosives that where used.

So far, nothing else that has been presented in the government reports, does not stand up to creditable science, and is not accepted by most scholars in the academic word of science.

NIST is nothing but a political lie.

I am not sure I understand your logic here,
You are saying that 17 floors of steel and concrete dropping on top of the rest of the building would not bring it down?

remember the floor trusses were only channel welded at the core and bolted at the outer colums
they were not solid beam construction there were truss support with a Z supporting bar NOT solid.

lets say each floor can support X (with X being the weight of 5 floors)

The 93rd floor would have had the load of 3.4X dropping onto it
3.4 times the amount it could support.
each floor in turn would have had an additional load added to it by the rest of the wieght dropping on to it.

Even given Griff's FoS of 2.5 , 3.4X exeeds that

posted on Mar, 17 2009 @ 07:21 PM

Originally posted by WonderwomanUSA
CameronFox, that airplane could have slammed through the whole building, taking out the entire core columns with it

Just for the record, there's no possible way those planes would have went through or even destroyed the cores. The planes didn't even destroy the outer columns. The planes were only able to enter the buildings because the outer columns were severed at their connectors.

Originally posted by Achorwrath
That could account for people saying the colums were cut in half

That could very well be. If you look at the bigger pictures, you'll even see one or two columns missing because they got separated from the plates that hold them together. You can see some of the columns starting to separate from their plates. But none of the outer columns actually failed, far as I can tell.

posted on Mar, 17 2009 @ 08:05 PM

Originally posted by _BoneZ_

Originally posted by WonderwomanUSA
CameronFox, that airplane could have slammed through the whole building, taking out the entire core columns with it

Just for the record, there's no possible way those planes would have went through or even destroyed the cores. The planes didn't even destroy the outer columns. The planes were only able to enter the buildings because the outer columns were severed at their connectors.

Originally posted by Achorwrath
That could account for people saying the colums were cut in half

That could very well be. If you look at the bigger pictures, you'll even see one or two columns missing because they got separated from the plates that hold them together. You can see some of the columns starting to separate from their plates. But none of the outer columns actually failed, far as I can tell.

Well... they did fail as a single structure but I see what you are saying the individual pices did not fail.

on the other hand the internal core colums were tapered and also connected in a similar manner, it is possible if the plane hit a colum along a weld that or joint that it could fail and account for the witnesses statements about colums cut in half.

Just speculation on my part there but as we know the internal core colums (beams) were not continuous but were welded or bolted together it still fits the evidence.

Which brings up the failure of the bolts and welds connecting things, I said it earlier... A structure is only as strong as its weakest point.

[edit on 17-3-2009 by Achorwrath]

posted on Mar, 17 2009 @ 08:16 PM
reply to post by Achorwrath

I am not sure I understand your logic here,
You are saying that 17 floors of steel and concrete dropping on top of the rest of the building would not bring it down?

Who said the concrete fell on anything, oh yes, NIST, ya right, my eyes saw the top of that building “VAPORIZED” and that is what we all had seen in every video taken that day, on 911.

So why do we want to take the word of a proven liar (NIST) why can’t you all trust what you see, or does the world need to be convinced that they are all to stupid to not know what an explosion is when they see one. Don’t you all know when you all have been HOODWINKED!

posted on Mar, 17 2009 @ 09:11 PM

Originally posted by WonderwomanUSA
reply to post by Achorwrath

I am not sure I understand your logic here,
You are saying that 17 floors of steel and concrete dropping on top of the rest of the building would not bring it down?

Who said the concrete fell on anything, oh yes, NIST, ya right, my eyes saw the top of that building “VAPORIZED” and that is what we all had seen in every video taken that day, on 911.

So why do we want to take the word of a proven liar (NIST) why can’t you all trust what you see, or does the world need to be convinced that they are all to stupid to not know what an explosion is when they see one. Don’t you all know when you all have been HOODWINKED!

I am not sure what video you saw, nothing was vaporized....

I do think I mentioned NIST, so where you are getting that from I am again not sure,...

The video I and I am sure most others watched showed the top flors tilting, then bucking then dropping down....
Vaporization means that is simply turned to vapor ( hence the name ) which it did not do...

Please post a link to the video you are refering to where it vaproizes (something that usually only liquids can do)...

posted on Mar, 18 2009 @ 12:05 AM
reply to post by Achorwrath

My apology, wrong choice of words the word I meant to use was “disintegrated.”
I notices there where no slabs of concrete falling do you see any slabs of concrete it all appears to have been pulverized in mid air

Fireman recalls that everything had 'collapsed to dust'
Firemen recall 'detonations' in South Tower

911research.wtc7.net...

posted on Mar, 18 2009 @ 06:34 AM

Originally posted by WonderwomanUSA
reply to post by Achorwrath

My apology, wrong choice of words the word I meant to use was “disintegrated.”
I notices there where no slabs of concrete falling do you see any slabs of concrete it all appears to have been pulverized in mid air

Fireman recalls that everything had 'collapsed to dust'
Firemen recall 'detonations' in South Tower

911research.wtc7.net...

Thank you for the calrification; however those two quotes are taken out of context. What tunred to dust? what exactly are they refering to? We do not know as the quote from the firemen is three words.

So my quote of:

WonderwomanUSA said she made a "wrong choice"

While still a valid quote, as you did say "wrong choice", is not accurate as it does not include what you are talking about and brings people to a missleading impression about the actual statement.

The slabs are the floors you would not see them as they are inside the building.

As we have alreay discussed they sit on top of the floor trusses (and are connected to knuckles along them.)

Did you expect them to slide out the side of the building?

As for the dust you see that is most likely the outer facia (which was concrete if I remember correctly). Smash concrete and it will create dust.

In your own videos I stll see the upper floors for some time.

In the first video at 00:03 you see the upper floors of the left hand tower lean to the left and you begin to see the lower concrete facia begin to crumble.

You can tell this is the buildings upper floors as you can see the soli line of the front facing corner. No disintegration there.

At 00:05 you can see the out line of the roof again the upper floors of the left hand tower are leaning dramtically to the left while the bottom is collapsing down onto it self impacting the floors below.

At 00:06 you can clearly see the roof at the top of the darker cloud of dust.

After that it is no longer visible

So in a 13 second clip the upper floors of the tower in question are visible for at least 6.

Also the announcer says almost as soon as the clip starts "Appearing to fall away from the rest of the buildings"

[edit for clairity]

[edit on 18-3-2009 by Achorwrath]

posted on Mar, 18 2009 @ 07:08 AM
North Tower Video Number one,
As soon as you start the clip you can see the upper floors dropping down onto the lower floors. Dust billows outward as they continue down.

At 00:02 you can very clearly see the rupper floors and the flames being pushed out of the side of the tower

The line of fires remain until 00:04 when they drop out of frame, the antenna is still visible pointing up.

A little past 00:07 you can see a corner of the building it is a white verticle line in the mass of dust and smoke, it stays visible until 00:08

posted on Mar, 18 2009 @ 07:33 AM
take a look at the first north tower clip with a video editing application (where you can break it down bellow 1 second) At 00:00:17 you can see dust begin to push out of the sides. if the floors were giving way this would happen as they would force air, dust and smoke out the windows.

This effect is very evident at 00:00:20 - 00:0022 where the dust can bee seen to be shooting out, this is before any outward indication of the upper floors moving. that does not happen until between 00:0026 and 00:01:01.

In the South Tower video at 00:02:16 you can see a line of white dust just below the line of black smoke, this is the facia giving way under stress and the colums it is attached to bend outward. At 00:03:02 is is very clear and you can see the line of the front facing corner begin to shift out of true. By 00:03:14 is is anout 10 degrees or so off of the straight line.

At 00:03:24 you can see the dust being forced out from inside the building and the corner is even further out alignment with the lower floors.

At 00:04:22 again I see the roof and upper floors at an odd angle and dropping down.

At no time did I see the upper floors Turn to Dust before impacting the lower floors.

Both videos clearly showed the upper sections of the towers dropping down and impacting the lower floors.

I used Adobe Premire Pro to view this in this manner.

My analysis of the videos before this post were done with Media Center.

posted on Mar, 18 2009 @ 12:11 PM
Hi Have said this before and will say it again look at the collapse videos.
The second tower hit collapsed first WHY simple look at the video of the collapse you see all the floors above the impact area drop as one MASS the floors they impact on CANNOT and were not designed with such a dynamic load in mind. The load was far greater above the impact point so that tower although hit second collapsed first.
Same happens with first tower look at the videos the floors above impact area drop as one MASS now each floor weighed approx 1500 TONS.
With regard to the fires the STEEL did not have to melt only weaken then the imposed load of the floors above bacame to much and down it went.

Have a look at this video

www.youtube.com...

At 5.13 probably gives the the best view you can see the building starting to collapse at impact area and the area above fall as one mass.

[edit on 18-3-2009 by wmd_2008]

[edit on 18-3-2009 by wmd_2008]

posted on Mar, 18 2009 @ 12:53 PM

Originally posted by wmd_2008
Hi Have said this before and will say it again look at the collapse videos.
The second tower hit collapsed first WHY simple look at the video of the collapse you see all the floors above the impact area drop as one MASS the floors they impact on CANNOT and were not designed with such a dynamic load in mind. The load was far greater above the impact point so that tower although hit second collapsed first.
Same happens with first tower look at the videos the floors above impact area drop as one MASS now each floor weighed approx 1500 TONS.
With regard to the fires the STEEL did not have to melt only weaken then the imposed load of the floors above bacame to much and down it went.

Have a look at this video

www.youtube.com...

At 5.13 probably gives the the best view you can see the building starting to collapse at impact area and the area above fall as one mass.

[edit on 18-3-2009 by wmd_2008]

[edit on 18-3-2009 by wmd_2008]

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.

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