Why Should the WTC Towers Suffer Complete Collapse?

A series of related arguments concerning the collapse of WTC 1 & 2 posits that the collapse mechanism is the weight of the upper building masses, which drove the destruction of the towers after the initiation events. In numerous threads and papers, posters as well as qualified engineers on both sides of the issue of 9/11 CT have attempted to quantify and elaborate the destruction of the towers in precise terms.

While I admire these efforts, I have always been struck by the obvious disconnect between these attempts at theoretical modeling, as well as the shorthand argument that "the falling upper building masses drove the collapse of the towers," and the reality of the collapses themselves.

Let's let this photo serve for this discussion:





Here we encounter the basic problem: I do not see any "huge mass falling and pulverizing the mass below." I see the immediate remnants of the upper building mass being ejected outward and the concrete being turned to dust.

The majority of the upper building mass simply no longer exists to drive the collapse. It is being strewn across the WTC site.

Now, since most of the upper mass is being "liberated" in this manner, what mass is then continuing to drive the collapse?

And how did the collapse continue at the rate it did?

We also know that the structural members--the core and perimeter columns--become much thicker toward the bottom of the buildings to support the upper mass. Why then, without 1/2, or, about a second later, 3/4 of the upper mass pressing down on them, do the buildings continue to collapse? At their strongest point?

This to me is the proof so many 9/11 debunkers are asking for. It is staring us in the face in that photo, hidden in plain sight.

(This thread is adapted from a prior post on a related thread, but I believe it warrants a thread of its own as I have not seen it properly addressed.)

[edit on 18-1-2008 by gottago]

Well you know my take on it by now but please don't consider me a 'debunker'. I assure you I'm looking at everything presented to see what fits, what doesn't, how and why and I guarantee I'm not suggesting my ideas are the absolute facts of it.

Those lower column sections were certainly heavier so it's no surprise to see multiple stories of the outer walls still standing fairly intact once the dust settled but there's evidence of the forces involved in the way they're all leaning outward, not inward. Enough force to propel the upper thinner sections of outer wall horizontally? quite possibly (note I'm not saying definitely).

edit for lousy typing

[edit on 18/1/2008 by Pilgrum]

Originally posted by Pilgrum
Those lower column sections were certainly heavier so it's no surprise to see multiple stories of the outer walls still standing fairly intact once the dust settled but there's evidence of the forces involved in the way they're all leaning outward, not inward. Enough force to propel the upper thinner sections of outer wall horizontally?

First you need to differentiate between torque imparted from gravity + instability, and an actual projectile motion from debris being literally launched out of the building.

If a perimeter column tilted outwards, its bolts broke, and it started falling, then it would do so right next to the building. It would not begin to lean and then suddenly be launched out horizontally, unless by a separate mechanism.

I think that we can tell from the lack of response here that there is no real way to answer your question without claiming the use of demo charges.

Design fault / shoddy workmanship?

The conspiracy they dare not mention ....

I just want to know what happened to the columns? Why would they be snapped like twigs? They were clearly the strongest point in the buildings, and if the building is going to collapse at the weakest point, the columns should have been left unaffected?

Right?

*Edited for spelling, then re-edited to add why I edited.
[edit on 19-1-2008 by Sublime620]

[edit on 19-1-2008 by Sublime620]

Originally posted by bsbray11

If a perimeter column tilted outwards, its bolts broke, and it started falling, then it would do so right next to the building. It would not begin to lean and then suddenly be launched out horizontally, unless by a separate mechanism.

Would falling debris striking the inside of the exterior columns be able to deliver enough force to propel them?

I believe I read a post that only a couple of thousand pounds of force would be sufficent to propel them a few hundred feet.

So if a falling 30 ton section of exterior column hit an exterior column below that has had its floors stripped off, wouldn't it be possible that enough energy could be imparted to it to "launch"?

Originally posted by Richard Gizinu
Would falling debris striking the inside of the exterior columns be able to deliver enough force to propel them?

No. Maybe in isolated cases but not for ultimately ~80% at least of the entire mass of either building. The collapse would have to literally have more momentum for every floor horizontally than vertically. In other words the mechanism's motion is not straight down, but straight out, each floor popping out one-by-one.

Originally posted by Sublime620
I just want to know what happened to the columns? Why would they be snapped like twigs? They were clearly the strongest point in the buildings, and if the building is going to collapse at the weakest point, the columns should have been left unaffected?

Right?

[edit on 19-1-2008 by Sublime620]

Core columns? They broke at the welds.

The core columns were maunfactured in 3 floor lengths - 30 ft? Then welded together as it went up. The welds were sometimes only on 2 sides, and weren't fully penetrating welds. This would have been sufficent since the core columns were never intended to take bending loads ( how's that for an accurate term?), just vertical gravity loads.

Exterior columns broke apart at the bolted connections.

Originally posted by bsbray11

No. Maybe in isolated cases but not for ultimately ~80% at least of the entire mass of either building. The collapse would have to literally have more momentum for every floor horizontally than vertically. In other words the mechanism's motion is not straight down, but straight out, each floor popping out one-by-one.

But not 80% of the debris was ejected 100's of feet. Some fell close, some was propelled.

So some peeled and fell close, like in your first post, and in some isolated cases, some was hit and propelled. Some farther than others.

Possible?

Originally posted by Richard Gizinu
But not 80% of the debris was ejected 100's of feet. Some fell close, some was propelled.

If you want to turn this into semantics, you go right ahead, but it is obvious from images what physically happened. That's all that matters. When I look at the piles left in the footprints, I don't care if some debris is just barely "over the line", so to speak.


Here is a diagram FEMA offers you:




Here is the little that was left in WTC1's footprint:





Here are only a few photos of ejected steel laying all over the complex and beyond:








The core structure is still partially intact at the base, which is mainly why there is as much debris in it as there is. And since the core is intact, and you can see that the perimeter walls (just at the lobby level) are also still intact, you get the idea that the debris did not go down much further than this. And in fact if you look at photos of the basements being excavated, it's mostly aggregate and still-intact structure.

WTC2 had even less debris in its footprint:

So some peeled and fell close

"Some" is so much more vague of a word than the percentages I was using for estimations. Can you be more specific?

and in some isolated cases, some was hit and propelled. Some farther than others.

No, now you're attempting a complete reversal of what I've said. You now suggest most debris landed in the footprints, or within a few feet of the footprints. I'd like to see visual evidence of this, in images from Ground Zero, please.

[edit on 19-1-2008 by bsbray11]

Originally posted by Richard Gizinu
Core columns? They broke at the welds.

Can you provide examples in the form of photographs and explain the mechanism that lead to their "breaking"?

And can we agree that a large steel box column will be under enormous stress before it fails, and that it will bend and deform greatly around where it actually severs?

Originally posted by Richard Gizinu
Core columns? They broke at the welds.

The core columns were manufactured in 3 floor lengths - 30 ft? Then welded together as it went up. The welds were sometimes only on 2 sides, and weren't fully penetrating welds. This would have been sufficent since the core columns were never intended to take bending loads ( how's that for an accurate term?), just vertical gravity loads.

Exterior columns broke apart at the bolted connections.

Would you please post the sources of your description about how the core was constructed?

Also, your contention that the cores were only intended to bear gravity loads is misleading, as the entire building was designed to sway in response to wind loads. I can personally attest to this as I'd visited once on a windy day and stood at the corner of one tower and could actually see the building sway. Quite a sight. Here is an analysisconcerning the wind loads only in relation to the perimeter columns:

With regard to the WTC’s perimeter columns, the factor of safety fluctuated from day to day and even from hour to hour, because, in addition to supporting 47% of the WTC’s gravity load, the perimeter wall also had to withstand the lateral force of the wind, which is highly variable given the whims of Mother Nature. A single face of the WTC presented an enormous “sail” to the elements, for which reason John Skilling vastly overbuilt this part of the structure. According to the NIST report, the outer wall’s factor of safety against wind shear on 9/11 was extraordinary, i.e., in the 10-11 range.[67] Why so high? The answer is simple: On the day of the attack there was essentially no wind, only a slight breeze.[68] For this same reason nearly all of the perimeter wall’s design capacity was available to help support the gravity load. As the NIST report states, “On September 11, 2001 the wind loads were minimal, thus providing significantly more reserve for the exterior walls.”[69] When NIST crunched the numbers for a representative perimeter column in WTC-1 (column 151, between the 93rd and 98th floors), they arrived at a factor of safety of 5.7.[70] Assuming this average figure is a typical value we arrive at a reasonable estimate of the perimeter wall’s amazing reserve capacity. Even if we subtract those columns severed/damaged by the impact of Flight 175, and the lost capacity due to the alleged (but unproven) buckling along the eastern perimeter wall, there was still a wide margin of safety, more than enough by several times over to support the outer wall’s share of the gravity load, with plenty to spare.[71]

The WTC’s tremendous reserve capacity was no secret. In 1964, four years before the start of construction, an article about the planned WTC appeared in the Engineering News-Record. The article declared that “live loads on these [perimeter] columns can be increased more than 2,000 percent before failure occurs.”[72] A careful reading of the piece also gives insight into why the plane impacts were not fatal to the integrity of the outer wall. The reason is simple: the perimeter columns were designed to function together as an enormous truss, specifically, a Vierendeel truss. The wall was inherently stable. After the plane impacts it behaved like an arch, simply transferring the load to the surrounding columns.

reply to post by bsbray11


Your whole argument is based on incredulity.

Try explaining WHY you feel this way.

Originally posted by Richard Gizinu
Your whole argument is based on incredulity.

Which argument would that be? "Look at the picture" or "put up or shut up"? Because that's pretty much all I just said.

Try explaining WHY you feel this way.

Try looking at the photos and justifying your statement that steel was only ejected in "isolated cases."

reply to post by bsbray11


Thanks bsbray for posting this series of photos of the aftermath. The OP made a very simple, basic point, and let's not lose sight of it:

Since the major mass of the towers did not fall directly on the remaining structure, how could this "ground zero" occur?

Where is the mass, the force, that drove the collapse to its conclusion?

Look at the photo in the OP again--the top of the building just wasn't there.

Originally posted by bsbray11

Can you provide examples in the form of photographs and explain the mechanism that lead to their "breaking"?

And can we agree that a large steel box column will be under enormous stress before it fails, and that it will bend and deform greatly around where it actually severs?

I could find the photos, but it's a pain. They're on Mark Robert's site.

I'm not an engineer, but the photos are the proof that it happened.

No, the columns broke at the welds, which were MUCH weaker, when exposed to lateral loads, then the core columns. That's why they don't show deformation.

Originally posted by gottago

Would you please post the sources of your description about how the core was constructed?

Also, your contention that the cores were only intended to bear gravity loads is misleading, as the entire building was designed to sway in response to wind loads.

The core columns were designed to take around 50% of the gravity loads.

The exterior columns were designed to handle the other 50% of the gravity loads and all the lateral loads. That doesn't mean that the building as a whole, wouldn't sway. The exterior columns handled these loads.

The floors connected the 2, and as a unit, performed as designed. But an unsupported core column has almost no ability to stand on its own when subjected to impacts .

Originally posted by bsbray11

Try looking at the photos and justifying your statement that steel was only ejected in "isolated cases."

Well aren't you the clever one.

Did I say that steel was ejected only in isolated cases? Nope.

To expand my statement, some would be impacted with sufficent force to be propelled 400 feet in isolated cases.

Some would be impacted with sufficent force to be propelled 300 ft....

Some...... 200 feet.....

Some..... 100 feet.....

And everything in between.

Some wouldn't be impacted at all, and would peel away as you said.

That's what your photos show.

Originally posted by Richard Gizinu
I could find the photos, but it's a pain.

I posted some photos above. You can't do the same?

I'm not an engineer, but the photos are the proof that it happened.

Exactly. All the columns and other structural debris laying all over the complex and in the streets and buildings beyond the complex were extensively photographed. So were the footprints of both buildings.

No, the columns broke at the welds, which were MUCH weaker, when exposed to lateral loads, then the core columns. That's why they don't show deformation.

The core columns were solidly welded to each other. You don't think deformation would occur in the surrounding steel before the ultimate strength would be reached in the welding? Do you know the difference between the ultimate strength and loading that just causes deformations?