Failure mode in WTC towers

[Furcifer]

I postulate as follows: These large perimeter sections seen falling before all others are from the 92nd to 98th collapse initiation zones.

Probably a little lower, but close enough unless you'e actually tracked this piece in photos and positively identified it.

They fall off the building as large perimeter pieces (spanning up to 5 or 6 floors)

Looks about right.

and do not appear noticably crushed, deformed or buckled.

and from that distance you wouldn't

We will get much higher quality photos and zoom in on these falling pieces.

This may prove difficult. Unless you can match that exact piece to one on the ground, nothing taken from further than a block away (with a Bronica) will give you the resolution you need to determine how "crushed, deformed or buckled" that piece is for purposes of proving anything beyond what is reasonable.

Reasonable being whatever Max doesn't say.

 

[Dave Rogers]

I postulate as follows: These large perimeter sections seen falling before all others are from the 92nd to 98th collapse initiation zones. They fall off the building as large perimeter pieces (spanning up to 5 or 6 floors) and do not appear noticably crushed, deformed or buckled.

OK, let's see if we can come up with an explanation of that. Suppose the columns initially buckle elastically, until they reach the elastic limit of the weakest part of the structure. That will probably be a weld or a bolt connection. At that point, the weakest point deforms plastically, releasing the elastic strain on the remainder of the column, which (because the strain is elastic) therefore returns to its original shape. When the points experiencing plastic deformation reach the point of fracture, the column section falls clear, and is seen as an undistorted - or substantially undistorted, there may be some slight buckling which will not be visible from a distant, poorly focused photograph of a moving object - column section with possibly some small region of plastic deformation close to its ends - which also will not be visible in a d.p.f.p.o.a.m.o. This is a simple and obvious explanation, and one that you have been offered several times before. In other words, what you are claiming as an anomaly is, in fact, no such thing, it is exactly what would be expected.

Dave

 

[Heiwa]

I am a critical thinker who respects genuine experts, especially when they have the ability to communicate some their knowledge to people who lack technical backgrounds. I am a harsh critic of ineducable, willfully ignorant charlatans who deliberately distort quotes and peddle bogus science in the service of an evil cause.

Very good, I am a critical thinker, too! Subject is failure mode, i.e. that the release of potential energy of the upper block above buckled columns (thus below the upper block) exceeded the strain energy of the structure (below).

The 280+ buckled columns in the initiation zone are not important! If they started to fail in the south wall, progressing through the east and west walls, etc (core ?) is of little interest. They are (incorrectly?) assumed to buckle and that is supposed to release potential energy. Dave Rogers think each column only deformed elastically prior two ruptures at top/bottom supports, so that the column straightened out afterwards. A bit fanciful - I have never seen such a column collapse once - and now it happened 280+ times, but who cares? What about the potential energy released.

How much is it? It is assumed that the upper block free falls down one floor level, 3.7 meters, and impacts the structure below. That is the alleged cause of the disaster.

If the upper block is 100% rigid, solid and the impact takes infinite time 340 kWh of energy is involved. It is not much! It will only elastically compress the structure below and maybe cause some plastic deformation of some parts due to overload. That is the effect! After that all potential energy is consumed. No global collapse of the rest of the structure can ensue.

However, Major Tom's & al's observations confirm my observation, i.e. that the upper block is not solid or rigid prior to the alleged impact.
It means that no impact of infinite time can take place! The energy is applied to the structure below over a longer time and then no sudden overload can take place as there is sufficient strain energy in the structure to handle that. Actually the whole upper block can be seen compressed 50% before anything happens to the structure below.

Reason how the upper block can compress 50% is that it is mostly air and of very low uniform density (0.18 ton/m3 initially). Question is of course why the upper block compressed or imploded prior impact? There was no load on it?

It appears that Nist, Bazant, Seffen and others make a serious mistake when they suggest that the upper block is solid/rigid before columns buckle, that the upper block free falls and impacts the lower structure as a rigid body and that the lower structure lacks strain energy to withstand the energy input from the rigid upper block.

Just correct these assumptions, e.g. that the upper block is not rigid at all and that, if the upper block impacts, it will self-destruct as it consists of floors bolted to columns acting as springs, and that contraption cannot cause any overload of structure below. Try then to prove that global collase ensues due to release of potential energy above from such a contraption. And explain the implosion of the upper block prior global collapse actually ensued.

 

[Newtons Bit]

The splices are staggered for the perimeter. What you are saying has no meaning in this case.

What you are saying is that you have no idea what you are talking about.

 

[Major_Tom]

OK, let's see if we can come up with an explanation of that. Suppose the columns initially buckle elastically, until they reach the elastic limit of the weakest part of the structure. That will probably be a weld or a bolt connection.

There is no need to speculate.

We know that the 98th floor (actually the 97th floor along the tops of the windows) seemed to give across the entire floor simultaneously along the west and north faces.

The external horizontal line along the perimeter that was seen to give first is well known.

At most, about 33% of the column-to-column bolted connections will be along this line.

The column-to-column bolt connections are staggered. It is impossible that the bolt connections stretch across the horizontal rows where ejections were first seen to come.

To get the crease of "buckling" and severence across the 97th floor ejection lines on the north and west faces, at least 66% of the columns from that row must buckle since there are no local bolt collections to break.

What we need are many higher quality photos of the leading large chunks of the falling perimeter to put NB and Dave's explanations to the test.

 

[GregoryUrich]

Major Tom:

Yes, but apparently Heiwa does.... he claims to see no tipping at all!

And there are no videos of the south face of WTC 1 during the collapse (as far as I know) but this would tell us a lot about the collapse!

This video from the north-west clearly shows the tilting if one watches the original Siegel footage which appears about halfway through.

 

[GregoryUrich]

Don't you wish you had a point to make?

The point was that there is no evidence what-so-ever that the top portion remained rigid or intact. You might as well just say what you never say "Oh, I guess you are right."

 

[beachnut]

The point was that there is no evidence what-so-ever that the top portion remained rigid or intact. You might as well just say what you never say "Oh, I guess you are right."

Gregory is an expert fence sitter who is listed under the Patriots Question for 9/11 truth. He signed a petition blaming US officials for the murders and of course he is a full blown truther with Scholars for 9/11 Truth & Justice a bunch of fence sitters who have nut case ideas on 9/11 and publish false information to blame others for 9/11. This alone is reason to know his word is independent and not biased on these issues. If you use judgment and knowledge you can use what Gregory says with a grain of salt.

 

[bofors]

This video from the north-west clearly shows the tilting if one watches the original Siegel footage which appears about halfway through.

(1) Where is the irrefutable evidence that tipping initiated the collapse of the North tower?

(2) What mechanism could have caused the near simultaneous failure of all the columns on the collapse initiation floor?

 

[GregoryUrich]

(1) Where is the irrefutable evidence that tipping initiated the collapse of the North tower?

(2) What mechanism could have caused the near simultaneous failure of all the columns on the collapse initiation floor?

1. Tipping is an observed phenomenon during initiation and does not imply an initiating mechanism.

2. I don't know.

 

[Dave Rogers]

(1) Where is the irrefutable evidence that tipping initiated the collapse of the North tower?

(2) What mechanism could have caused the near simultaneous failure of all the columns on the collapse initiation floor?

These questions are unusually absurd even by bofors standards. Tipping wasn't what initiated the collapse, it was a feature of the collapse; and tipping proves that the columns did not fail simultaneously. "Near simultaneously" is not worth commenting on, as it's a classic piece of truther obfuscation.

Dave

 

[Myriad]

(1) Where is the irrefutable evidence that tipping initiated the collapse of the North tower?

"Initiated?" Say, rather, that it was one step in the chain of events that made up the collapse. Some of those events happened quickly, some slowly. What initiated them was the high-speed crash of a jetliner into the upper floors. The tipping was caused by failure of some of the columns to support the increased loads on them. The tipping in turn caused redistribution of loads that led to further support failures. If you must place the "initiation" of the actual structural collapse in one moment, it's when the upper block first started to move. It began rotating at that point, so the initiation of collapse caused the tipping, not the reverse.

(2) What mechanism could have caused the near simultaneous failure of all the columns on the collapse initiation floor?

Progressive overloading of those columns.

http://www.internationalskeptics.com/forums/showthread.php?t=102994

Respectfully,
Myriad

 

[bofors]

1. Tipping is an observed phenomenon during initiation and does not imply an initiating mechanism.

From what I understand, the proponents of the gravity driven collapse theory are claiming that the collapses initiated with "rotating", "tilting" or "tipping" (which you should note is something completely different then what Bazant proposes and it implies the release of even less potential energy):

I think the upper block being rotated and striking the lower block in an angle might produce axial strikes that are not concentric, don't you? And of course, it's entirely reasonable that with even a minor rotation of the upper block, the upper block columns will not be striking the lower block columns at all.

(1) Again, there seems to be no evidence (irrefutable) of this in the north tower, is there any?

(2) Even if there is such evidence what resulting mechanism could have caused near simultaneous of all columns during the collapse initiation of the north tower?

 

[Dave Rogers]

From what I understand, the proponents of the gravity driven collapse theory are claiming that the collapses initiated with "rotating" or "tilting":

There's your problem, right there.

Can you understand the difference between "with" and "by"? Or when you get served roast beef with gravy, do you always give the waiter a suspicious glance?

Dave

 

[bofors]

Progressive overloading of those columns.

http://www.internationalskeptics.com/forums/showthread.php?t=102994

I am not sure why you think that answers my question about near simultaneous failure because, as you indicate in your linked thread, you believe that column failure was progressively horizontal:

It's clear that collapse initiation for both towers, and for WTC7 as well, were true progressive failures. In those cases the "progression" of the progressive failure was horizontal...

I do not believe there is any evidence of this in the north tower.

 

[beachnut]

expand on that

 

[Heiwa]

Tilting of the upper block does not cause any vertical collapse effect. Rather the oppositie. Tlting means to cause something into a sloping position, and if potential energy tilts the upper block before any downward motion starts (the official cause) , then most energy available will be lost in the tilting. The tilting energy is evidently directed sidewards as rotation and has no vertical component downwards.

Or for children. There is a weight (mass) on a table with three legs. You remove one leg and the table and the mass above tilts in the direction of the removed leg.

Nothing moves down below the intact two legs.

Or with a four leg table. Remove one leg ... and what happens? Nothing, if there is perfect balance. The other legs carry the weight of the missing leg.

But then there are only three legs left. Guess what happens when one of those collapses! You are right. Tilting! But the remaining two legs will remain intact. No vertical movement there.

 

[GregoryUrich]

From what I understand, the proponents of the gravity driven collapse theory are claiming that the collapses initiated with "rotating", "tilting" or "tipping" (which you should note is something completely different then what Bazant proposes and it implies the release of even less potential energy):

(1) Again, there seems to be no evidence (irrefutable) of this in the north tower, is there any?

(2) Even if there is such evidence what resulting mechanism could have caused near simultaneous of all columns during the collapse initiation of the north tower?

If you use a little geometry to examine the tilting, you can see that column-column impacts were nearly impossible due to displacement of the upper part.

The tilting itself is evidence that there was no near simultaneous collapse of all columns.

 

[Myriad]

I am not sure why you think that answers my question about near simultaneous failure because, as you indicate in your linked thread, you believe that column failure was progressively horizontal:

Yes, horizontal, and rapid, which adds up to "near simultaneous" (but not completely simultaneous, hence the tipping).

Horizontal -- when a column begins to fail, what happens to its load? It's transferred to the horizontally adjacent columns. If they, too, begin to fail under their now-increased load, then the columns horizontally adjacent to them receive the load. And so forth. The result is horizontally progressive failure.

Rapid -- Only in the movies are progressively failing systems required to pause for dramatic effect between stages. The redistribution of load forces moves at the speed of sound, which in steel is over 11,000 miles per hour. Once the forces on a column are greater than it (or its connections) can withstand, there's no reason for it not to fail immediately.

But you don't have to take my word for it. NIST modeled the conditions in Tower 1 (and Tower 2) and horizontal, progressive, near-simultaneous column failure is what the models showed happening as a result.

With continuously increased bowing, as more columns buckled, the entire width of the south wall buckled inward. Instability started at the center of the south wall and rapidly progressed horizontally toward the sides. As a result of the buckling of the south wall, the south wall significantly unloaded (Fig 5-3), redistributing its load to the softened core through the hat truss and to the south side of the east and west walls through the spandrels. ... The section of the building above the impact zone tilted to the south (observed at about 8°, Table 5-2) as column instability progressed rapidly from the south wall to the adjacent east and west walls (see Fig. 5-8), resulting in increased gravity load on the core columns.

(emphasis added)


So that's a progressive column failure ("instability" -- columns capable of withstanding their load are stable) progressing horizontally and rapidly across the south wall, then horizontally and rapidly via the hat truss to the core and horizontally and rapidly to the south sides of the east and west walls. During that process, tipping also began occurring.

You seem to think that "progressive" and "near-simultaneous" are contradictory attributes for a failure event. They are not (except, as I mentioned, in the movies). And that does answer your question about "near simultaneous failure," whether you like that answer or not.

Respectfully,
Myriad

 

[bofors]

If you use a little geometry to examine the tilting, you can see that column-column impacts were nearly impossible due to displacement of the upper part.

My question is how do the proponents of gravity driven collapse explain the first instance of such displacement.