WTC7 - The fires failed Girder 44-79

[jaydeehess]

While we waot for a truther scenario for CD...........

Last time I looked out my window at work, the Aon tower was still standing. Did it get hit by a plane and have a major fire, that I was unaware of?

When completed, it was the world's tallest marble-clad building, being sheathed entirely with 43,000 slabs of Italian Carrara marble. The marble used was thinner than previously attempted in cladding a building; this quickly proved to be a mistake. On December 25, 1973, during construction a 350 pound marble slab detached from the façade and penetrated the roof of the nearby Prudential Center.[8] In 1985, inspection found numerous cracks and bowing in the marble cladding of the building. To alleviate the problem, stainless steel straps were added to hold the marble in place.[7] Later, from 1990 to 1992, the entire building was refaced with Mount Airy white granite at an estimated cost of over $80 million.[4][9] (Amoco was reluctant to divulge the actual amount, but it was well over half the original price of the building, without adjustment for inflation.)

Wow a safety feature that was implemented at great cost rather than fake a terrorist attack to excuse its total destruction. Amoco acting prudently.

 

[jaydeehess]

Try this:
Somebody puts you in a box where you stand vertically feet on the bottom, head jammed against the top - reasons for head jamed should be obvious with what is coming. They give you a tennis ball then drop box plus you plus tennis ball off a high building.

Ignoring wind resistance (make it a streamlined box ) the lot goes to "G" or near enough.

Having nothing to do you decide to pass the time bouncing the tennis ball. So you throw it down to wards the bottom of the box.

What is the acceleration of the tennis ball:
a) As your arm/hand accelerates it to release speed?
b) at the instant after it is released?
c) When it strikes the floor of the box?
d) add more to suit your own thinking.

If you simply opened your hand the ball will not move any closer to the bottom of the box since both it and the bottom of the box are already falling at g due to gravity.

Thus in order to have the ball move to wards the floor of the box it requires that you push down on the ball. However Newton states that every action has an equal and opposite reaction and the amount of force you exert on the ball will equal the force causing your feet to rise off the floor. The saving grace in this is that the acceleration of your arm and ball moving down, wrt to the box, is proportional to both the force exerted and the mass of arm and ball which is itself much smaller than the mass of the rest of the body that is moving upwards, wrt the box. So while you move the ball down, your body accelerates slightly upwards but a much smaller acceleration than that of arm & ball. With your head jammed on the ceiling you however do not move and must absorb this force.

The ball accelerates while your arm accelerates but ceases acceleration at release(again wrt to the box) and now continues at a steady velocity , wrt the box, to wards the floor of the box.

The ball strikes the floor of the box and decelerates as it compresses due to its momentum and elasticity, thus storing energy which is released as the ball rebounds accelerating in the opposite direction. This acceleration ceases as soon as the ball is no longer in contact with the floor and the ball now moves to wards the ceiling at a steady velocity , wrt the box, where it hits the ceiling and rebounds again to wards the floor. For a perfectly elastic ball, it will continue to bounce between floor and ceiling.

Within the confines of the box, acceleration due to gravity plays no role in the velocity of the ball wrt to the box.

Here's the tricky part though. As the ball strikes the floor and rebounds its also pushing on the floor causing the box to accelerate slightly faster than g you say? Well not quite since pushing the ball downwards your head caused an upwards force at the contact of head on ceiling and at that time you slightly slowed the acceleration of the box.

Now if the box had a very large headroom;
as ball is accelerated down, you move upward. This is dictated by force generated by you and since a=F/m the larger mass of your body will experience a smaller acceleration than the ball does. The ball will then cease its downward accelleration (shall I keep saying 'wrt the box' ad infinitum?) when released and so will you but the ball is moving faster than you are and depending on distances involved, will reach the floor befor you reach the ceiling. When ball rebounds it will add a small force to the box causing it to now have a slightly greater than g acceleration, wrt the Earth, which will continue to be the case until you and/or the ball hit the ceiling and transfer momentum to the box over time.(a force)

 

[ozeco41]

Well done sir!

just one significant point and a couple of minor ones.

I see that you spotted why I had "head jammed up against roof".

Recall my question:

What is the acceleration of the tennis ball:
a) As your arm/hand accelerates it to release speed?

The ball accelerates while your arm accelerates but ceases acceleration at release(again wrt to the box)....

You correctly identified the a and v as relative to the box.

So what is the absolute relative to earth "acceleration of the tennis ball?" whilst it is being accelerated relative to the box? That was the one I was looking for given this example being used in the setting of "WTC7 collapse and probable accelerations in excess of 'G'".

So "High Credit" - I would have awarded "Distinction" if you had specifically addressed that one extra factor.

(I am treating the second order effects as of no consequence for purposes of this exercise - air resistance on the outside of the box also the upwards effect on box and person minus arm from exerting the downwards force on the ball and (later) the forces/accelerations/changes of momentum associated with rebound of tennis ball. Which is one reason I picked a tennis ball because its weight is second order at best - probably third compared with the total mass of box and most of the human. Plus "locking" the human in place by head jammed against roof.)

Are you still in hospital?

(And, for the cynics, this topic is directly relevant to WTC7 collapse because it is an exercise to explore the free body motions associated with the near free fall, free fall and 'over G' aspects of the WTC7 collapse.)

 

[LSSBB]

Will it collapse similar to WTC 1 if a jet crashed into it and fires left burning for over an hour?

How much will get through the marble façade? You do the math.

 

[ozeco41]

How much will get through the marble façade? You do the math.

The original marble failed due to heat effects and was replaced with granite - a costly exercise. It would not offer any substantial resistance to aircraft penetration in a repeated 9/11 scenario.

Superficially from initial google search the structure is similar tube in tube layout to WTC1 and WTC2. Haven't found any details so far. But it potentially has the same built in vulnerabilities as the Twin Towers viz:

A) impact and accumulated fire damage could possibly lead to a cascade failure stage as per the initiation of the collapses of the WTC "Twins".

B) The tube in tube set up also could be vulnerable to a ROOSD style progressive collapse.

Too many details and "what ifs" to take it further as an internet forum investigation IMO.

I wouldn't mind betting that the owners have done a bit of thinking following 9/11.

 

[LSSBB]

The original marble failed due to heat effects and was replaced with granite - a costly exercise. It would not offer any substantial resistance to aircraft penetration in a repeated 9/11 scenario.

Superficially from initial google search the structure is similar tube in tube layout to WTC1 and WTC2. Haven't found any details so far. But it potentially has the same built in vulnerabilities as the Twin Towers viz:

A) impact and accumulated fire damage could possibly lead to a cascade failure stage as per the initiation of the collapses of the WTC "Twins".

B) The tube in tube set up also could be vulnerable to a ROOSD style progressive collapse.

Too many details and "what ifs" to take it further as an internet forum investigation IMO.

I wouldn't mind betting that the owners have done a bit of thinking following 9/11.

Eh, you're probably right. In any case, there are no buildings built like the WTC 1 and 2 that had airplanes crash into them and catch on fire.

Have any tube in tube buildings been CD'd?

 

[beachnut]

Will it collapse similar to WTC 1 if a jet crashed into it and fires left burning for over an hour?

Are the fireproofing the same material?
Did you google this? What is your source that Aon is the same? Did they use wallboard to insulate the core? (which part is similar)

What is the shell made out of, the grade of steel? Will it stop a 186 pounds of TNT KE impact in a shape of a modern Jet? WTC would, is Aon stronger because it is shorter? Different thickness of steel?

What is the building made of wrt insulation? The WTC insulation did not survive the 1300 and 2000 pounds of TNT KE impacts. Are the owners of Aon dumb enough to give out the building plans to 911 truth nuts? If you want to be on watch list, ask. Is the steel covered in masonry? Bet you have more info, but forgot to publish the source.

Wait, this is WTC 7, you confirmed NIST got it right. Never-mind.

 

[ozeco41]

Eh, you're probably right. In any case, there are no buildings built like the WTC 1 and 2 that had airplanes crash into them and catch on fire....

...Have any tube in tube buildings been CD'd?

I'm pretty confident it is "No."

Whilst I have no direct knowledge:

A) The concept only goes back to ~1970's AFAIK; AND
B) If there had been one it surely would have been well publicised on these threads - by either side:
(i) Truthers saying "See - we told you so!" AND
(ii) Debunkers explaining why it was different.

So I am very confident about that "No."

 

[Gamolon]

Can you provide me with an example of a high rise completely collapsing solely due to fire.

To which I then asked:

Sure, as soon as you find us a few scenarios where we are comparing apples to apples.

First thing I'll ask you is this. Find me an example of a building that was either similar in design in to the twin towers or WTC7.

That was the first question. You provided the Aon Center as your example.

What about the Aon Center in Chicago?

Based on you selecting the Aon Center, I am assuming you are going to go with the twin tower scenario for the historical call for examples you have made in the first quote above.

Now for the second condition for comparing apples to apples. Find a building similar to the twin tower design AND that was hit by a jet in the upper third and caught fire.

How many examples can you find now?

 

[enik]

This is getting way off topic. Gamolon, please demonstrate your analysis skills over at my other thread.

 

[jaydeehess]

Well done sir!

just one significant point and a couple of minor ones.

I see that you spotted why I had "head jammed up against roof".

Recall my question:
You correctly identified the a and v as relative to the box.

So what is the absolute relative to earth "acceleration of the tennis ball?" whilst it is being accelerated relative to the box? That was the one I was looking for given this example being used in the setting of "WTC7 collapse and probable accelerations in excess of 'G'".

So "High Credit" - I would have awarded "Distinction" if you had specifically addressed that one extra factor.

(I am treating the second order effects as of no consequence for purposes of this exercise - air resistance on the outside of the box also the upwards effect on box and person minus arm from exerting the downwards force on the ball and (later) the forces/accelerations/changes of momentum associated with rebound of tennis ball. Which is one reason I picked a tennis ball because its weight is second order at best - probably third compared with the total mass of box and most of the human. Plus "locking" the human in place by head jammed against roof.)

wrt to the earth, when the ball is thrown downwards in the box, a force equivalent to that downward force acts upon the box via the person's head but in the opposite, upwards direction. Ball moves downwards faster than g but box itself now is accelerating at slightly less than g.

As ball is released this extra force stops and ball moves downwards at g and box again is accelerating at g.

ball hits floor and imparts a force due to impulse force (momentum transfer over the time of contact) thus (in our strictly first order assumption) imparting the same force on the box that was imparted upon the ball and during this transfer of momentum the box accelerates at slightly more than g..
Note that over the entire length of time that all of this occurs, from beginning to throw the ball until the ball finishes transfering momentum to the box floor, the average acceleration of the box is g

 

[jaydeehess]

Now move along to the case of an inclined beam with an object sitting on the high end of the beam, unattached but blocked from sliding down the beam?

The beam is then allowed to fall to ground. What is the acceleration of the high end of the beam?,, the point at its center of mass? What is the acceleration of the unattached object?

 

[ozeco41]

Now move along to the case of an inclined beam with an object sitting on the high end of the beam, unattached but blocked from sliding down the beam?

The beam is then allowed to fall to ground. What is the acceleration of the high end of the beam?,, the point at its center of mass? What is the acceleration of the unattached object?

Yes. I've lost my link to that classic video clip - it will be recorded on one of my"bits of paper" somewhere. pgimeno some months (years?) back referred to a crane jib collapse which was a IIRC a practical example of the pivoted lever cup and ball demonstration.

Bottom line >>'G' is not a mystery.

 

[ozeco41]

Ball moves downwards faster than g but box itself now is accelerating at slightly less than g....

which was my main point when I first posted the "thinking exercise".

IIRC I got little or no response which says something about "thinking' v "parrotting".

 

[Gamolon]

This is getting way off topic. Gamolon, please demonstrate your analysis skills over at my other thread.

Sorry, but I'll just use an excuse that one of my other buddies used earlier...

...way more than I wanted to commit.

Anyways, that's not my area of expertise. There are many people here in this forum that are way more qualified than I when creating models and doing calculations.

 

[ozeco41]

This is getting way off topic. Gamolon, please demonstrate your analysis skills over at my other thread.

All this recent stuff is relevant basics.

But the narrow "on topic" status is:
1) WTC7 collapsed as a consequence of fire damage;
2) The only variant from that is in claims of CD;
3) There has never been an hypothesis for CD;
4) Therefore OP claim of "fires failed Girder 44-79" is either:
(i) the unfalsified standing hypothesis if you want pseudo scientific language; OR
(ii) "true" in layperson talk.

PLUS
5) There has been a lot of talk about the specific details - both in support of and in opposition to NIST - none of them any more persuasive than the NIST hypothesis.

However a lot of speculation has been about accelerations at or about "G" hence the reprise discussions of the basic physics.

 

[jaydeehess]

Yes. I've lost my link to that classic video clip - it will be recorded on one of my"bits of paper" somewhere. pgimeno some months (years?) back referred to a crane jib collapse which was a IIRC a practical example of the pivoted lever cup and ball demonstration.

Bottom line >>'G' is not a mystery.

'zactly and given both your pointing out the effect of collissions and the effect of rotation. there is, from a basic physics stance, going to be variations in the observed acceleration of various parts of the structure.
Add to this the observed established fact that some locations of the building managed to exceed g and it would become obvious even to a high school physics student or his teacher, that such effects were in play and to a degree that was significant enough to affect observational measurements..

or

that some other unobserved source of downward force was in play, the realm of fiction. Fiction is easy so I'll have a go. The core area under the roof top was collapsed only to the 40th floor creating a hidden area in the recess. Large doors then opened from the ceiling of the 39th floor pushing aside the debris on the floor of the 40th.Enormous hydrogen/ oxygen rocket motors then fired creating a downward force on the floorspace of the 39th floor. While this was occurring, therm?te was burning through all interior columns at a lower, 8 or below, level.
Thus collapse achieved and exceeded g, only water vapour was created by the rocket motors which is not unusual in the debris since fire fighters immediately doused the debris and there was already a huge amount of smoke in the vicinity.
Yeah there are a few minor holes in my story but it is fiction after all . If Kirk et al can flit about the galaxy at many times the speed of light then I can propose the above! ... and that's the story I'm sticking with!¡

 

[ozeco41]

...and that's the story I'm sticking with!¡

I'm with you...


...however

Enough for now. Let's see if anyone can post directly on the topic. Current status is the OP stands - "WTC7 - The fires failed Girder 44-79" - because there is no opposing hypothesis.

 

[jaydeehess]

Let's see if anyone can post directly on the topic. Current status is the OP stands - "WTC7 - The fires failed Girder 44-79" - because there is no opposing hypothesis.

You mean other than those proposed in posts 851 and 897?

 

[LSSBB]

You mean other than those proposed in posts 851 and 897?

Congratulations, jaydee, you move to the head of the Truther class.