structural engineer leslie robertson interview, page 1

www.bbc.co.uk...

hi...ive just stumbled across these interviews with him and one thing jumps out..at least to me...why..in the IMPACT OF A PLANE section does he say the 707 would have had a far smaller fuel load as it was a 'landing' aircraft?

does that make sense to anybody?

reply to post by alienesque

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Leslie also went on to say that they couldn't have forseen what the jet fuel would've done to the buildings. I say HUH? They designed the buildings to withstand jetliner impacts, but couldn't forsee what the jet fuel would do? Leslie was obviously and blatantly lying, probably trying to cover his buttocks.

WTC constuction manager Frank DeMartini said otherwise. He said the buildings were designed to withstand FULLY LOADED jetliners. Believe one or believe the other. The buildings were still designed to withstand them, and they did before explosives brought them down.

reply to post by alienesque

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You mean how they assumed that the only way such a collision would be a result of an airliner landing in the fog? Did you ever think that the normal takeoff patterns from the area airports are structured so that an airliner taking off wouldnt create the same possibility?

reply to post by CameronFox

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Although the 767-200 that impacted the south tower is slightly larger than a 707, the 707 is heavier and faster than a 767-200.

707:
www.flugzeuginfo.net...

767-200:
www.flugzeuginfo.net...

Further, Mr. DeMartini said fully loaded. That means fuel, passengers, luggage, etc.

Originally posted by CameronFox
Once again, we did not have the ability to model what damage would be caused by the fires.

Why? Because Leslie Robertson says so?

Their work led 127 years later to Sadi Carnot, the "father of thermodynamics", who, in 1824, published Reflections on the Motive Power of Fire, a discourse on heat, power, and engine efficiency. The paper outlined the basic energetic relations between the Carnot engine, the Carnot cycle, and Motive power. This marks the start of thermodynamics as a modern science.[3]

The term thermodynamics was coined by James Joule in 1849 to designate the science of relations between heat and power.[3] By 1858, "thermo-dynamics", as a functional term, was used in William Thomson's paper An Account of Carnot's Theory of the Motive Power of Heat.[11] The first thermodynamic textbook was written in 1859 by William Rankine, originally trained as a physicist and a civil and mechanical engineering professor at the University of Glasgow.[12]

en.wikipedia.org...

So, in over 100 years, we hadn't learned anything about what heat does to materials?

reply to post by Griff

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Leslie was trying to cover his arse or cover things up, plain and simple.

reply to post by CameronFox

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Your kinetic energy means absolutely nothing by itself.

Remember when objects collide the force on each object is equal, regardless of the 'kinetic energy', see Newtons laws. The object with the most mass will receive the least damage. So if the aircraft were destroyed by the steel, then the plane cannot also destroy the steel.

Now if the plane was made of material that had more mass than steel, then the speed would make a difference, but not in the way you're thinking.

Do you understand this?

(same theory explains why there was NO plane at the pentagoon, think about it).

Also, as Griff pointed out, we have known what jet fuel does to steel looooong before 9-11 happened. Thus, Robertson is full of it.

[edit on 3/16/2009 by ANOK]

When WTC was designed in 1960's nobody could concieve that 30 years
later bunch of fanatics would crash planes at 500 mph into buildings

Only reason designers could think of why an airliner would be flying that
low (under 1300 ft) over Manhattan was a plane lost in fog/bad weather
descending into the airports (Laguardia or JFK).

In fact had already happened not once, but TWICE!

First in 1945 when B25 lost in fog ploughed into Empire State Building

en.wikipedia.org...

Year later (1946) another lost aircraft, Coast Guard C 45 transport, again
lost in fog smashed into 40 Wall Street

en.wikipedia.org...

Had historical precedents of 2 lost aircraft hitting buildings, both flying
low and SLOW!

Designers made quick calculations of aircraft size (707) and speed (>180mph) to see if building could withstand impact

As for fuel load - was no way in 1960's to model fire behaviour. Only in
last few years were computers powerful enough to do it.

Originally posted by ANOK
reply to post by CameronFox

---

Your kinetic energy means absolutely nothing by itself.

Remember when objects collide the force on each object is equal, regardless of the 'kinetic energy', see Newtons laws. The object with the most mass will receive the least damage. So if the aircraft were destroyed by the steel, then the plane cannot also destroy the steel.

Now if the plane was made of material that had more mass than steel, then the speed would make a difference, but not in the way you're thinking.

Do you understand this?

(same theory explains why there was NO plane at the pentagoon, think about it).

Also, as Griff pointed out, we have known what jet fuel does to steel looooong before 9-11 happened. Thus, Robertson is full of it.

[edit on 3/16/2009 by ANOK]

You seem to be confusing head on impact of two moving objects with a moving object hitting a stationary object.

Upon impact of a moving object with a stationasy object the moving object will attempt to transfer its kinetic energy to the stationary object the stationry object will resist this with it mass.

However since speed (or acceleration) artifically increases the force (mass) of the moving object you cannot make the blanket statment that a 767 with a wieght of 400,000 Lbs would have "no effect"

If this is the case then why can a car wieghing 3200 Lbs demolish a house wieghing 10,000Lbs in a collision..

When the plane hit it had a force in excess of 100,000,000 Lbs. this visbily damaged the outer later sway support on one axis. It can also be deduced that the many of connecting floor beams across eight floors (93-101 for WTC1) were now without support. The concrete slabs of the flooring (sitting on top of the floor beams) were also unsupported.

People inside the building (below and on floor 93-95 and above) noted that the stairwells and elevator shafts were damaged. (one person claimed to have jumped down from one floor to another as the stairwell was cut in half) this indicates there was also damage to the central core of the building.

Now we have a visible damage to the outer lateral sway support, diconnected floor beams, and probable central core damage.

Considering that JA1 (JP5) burns in open air at 287.5C (549.5F) and steel (of 2.1% carbon also called structural steel) begins to weaken (not melt but weaken) at 230C and generally looses 10% strength at this point.

you can see how it is more likely that the fire, did not cause the collapse but was a contributing factor.

Originally posted by ANOK
Your kinetic energy means absolutely nothing by itself.

Now if the plane was made of material that had more mass than steel, then the speed would make a difference, but not in the way you're thinking.

Do you understand this?

I understand perfectly....it must have been a giant pumpkin that hit the Pentagon. For someone that claims to know "basic" physics... well...

Originally posted by Achorwrath
Considering that JA1 (JP5) burns in open air at 287.5C (549.5F) and steel (of 2.1% carbon also called structural steel) begins to weaken (not melt but weaken) at 230C and generally looses 10% strength at this point.

Why do you keep posting this?

The fire temperature....fire......fire....fire.

Steel takes an amount of time to reach this temperature in a fire.

Instead of assuming that the steel did in fact reach this temperature just because the fire can reach that temperature, let's ask NIST who actually found the temperature of the steel in the fire affected floors, eh?

What did NIST find?

Oh, and please explain how a 10% loss of strength causes a collapse when the Factor of Safety of buildings is over 2.5.

Also, can you please show where ANOK said anything close to "no effect". Or admit you put those words in his mouth.

[edit on 3/17/2009 by Griff]

[edit on 3/17/2009 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?

Same as what happened at the towers. The force of the plane was enough to cause the bolts and welds to fail. But, there wasn't an actual cartoon cut-out in the steel. It just looked that way from how the columns where constructed in sets of threes.

But, the point is that the plane did not "punch" through the steel other than the parts that are stronger than the steel (i.e. the engines etc.). What it did was "push" the steel out of the way.

Same as what the pumpkin is doing to those vehicles. Except for the fiberglass boat which is being hit in the weak axis and thus breaking. Fiberglass is weak in bending moment (being hit by something perpendicular to the "grain" of the fiberglass).

Edit: I'm trying to find the picture of the columns that were pushed into the street by the plane. You can see what I'm talking about more clearly.



[edit on 3/17/2009 by Griff]

[edit on 3/17/2009 by Griff]

Originally posted by Griff

Originally posted by Achorwrath
Considering that JA1 (JP5) burns in open air at 287.5C (549.5F) and steel (of 2.1% carbon also called structural steel) begins to weaken (not melt but weaken) at 230C and generally looses 10% strength at this point.

Why do you keep posting this?

The fire temperature....fire......fire....fire.

Steel takes an amount of time to reach this temperature in a fire.

Instead of assuming that the steel did in fact reach this temperature just because the fire can reach that temperature, let's ask NIST who actually found the temperature of the steel in the fire affected floors, eh?

What did NIST find?

Oh, and please expalian how a 10% loss of strength causes a collapse when the Factor of Safety of buildings is over 2.5.

Also, can you please show where ANOK said anything close to "no effect". Or admit you put those words in his mouth.

[edit on 3/17/2009 by Griff]

The factor of 2.5 was not in effect in buildings built in the 1960s,
Please show me you evidence for this being the building standard in effect when the WTC towese were constructed (the actual regulations were between .8 and 1.5) the WTC was not built with a FoS of 2.5 as claimed.

since you want to bring NIST into it:

1.67 and 1.92 for core columns in the original design and SOP cases, and for all columns in
refined NIST estimate case.
• 1.26 and 1.44 for perimeter columns in the original design and SOP case (discounting the
1/3 increase in allowable stress under wind loads)

source

One of your own posts states that the hottest temperatures the steel attained was not over 250C. still over the 230C that steel begins to weaken at.

I have explained at lenght how the FIRE COMBINED WITH STRUCTUAL DAMAGE casued the collapse, please show where I say that it is JUST THE FIRE or admit you put those words in my mouth

Anok said

Your kinetic energy means absolutely nothing by itself.

Remember when objects collide the force on each object is equal, regardless of the 'kinetic energy', see Newtons laws. The object with the most mass will receive the least damage. So if the aircraft were destroyed by the steel, then the plane cannot also destroy the steel.

Now if the plane was made of material that had more mass than steel, then the speed would make a difference, but not in the way you're thinking.

So yes you are right I used those excat words not Anok, however Anok saying that the steel detroying the plane indicates the impact did not affect the steel. Is an incorrect conclusion.

Also since it has been asked how the steel could have possibly been weakend by the fire; the open air burn temperature of an uncontrolled JA1 fire is relavent to the issue. Why do you want to discount it?




Edited for horrible typing and clarity]

[edit on 17-3-2009 by Achorwrath]

reply to post by Griff

---

Thanks Griff... I understand what you are saying. The point I was making...the Towers were stationary. If the Van was traveling toward the pumpkin at the same speed... damage would be different. Anok seems to think differently.

Also Griff... if you haven't read this, I think you may find this interesting:

The problem of the airplane wing cutting through the exterior columns of the World Trade Center is treated analytically. The exterior columns are thin-walled box beam made of high strength steel. The complex structure of the airplane is lumped into another box, but it has been found that the equivalent thickness of the box is an order of magnitude larger than the column thickness. The problem can be then modeled as an impact of a rigid mass traveling with the velocity of 240 m/s into a hollow box-like vertical member. The deformation and failure process is very local and is broken into three phases: shearing of the impacting flange; tearing of side webs; and tensile fracture of the rear flange. Using the exact dynamic solution in the membrane deformation mode, the critical impact velocity to fracture the impacted flange was calculated to be 155 m/s for both flat and round impacting mass. Therefore, the wing would easily cut through the outer column. It was also found that the energy absorbed by plastic deformation and fracture of the ill-fated column is only 6.7% of the initial kinetic energy of the wing.

Source:
How the airplane wing cut through the exterior columns of the World Trade Center; Wierzbicki, T.; Teng, X. International Journal of Impact Engineering; 2003 Vol. 28, p601-625.

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