Layman's terms please! Tower collapse issue

[Apollo20]

Sizzler

Yes, it's Heiwa's box spring bending. They also talk about it in the NIST Report (of course!)... sorry I cant give the reference, but I see RM can!

 

[Sizzler]

Thanks guys. Never noticed that before.

 

[MRC_Hans]

Sorry, you are totally wrong! How would the wall columns buckle without floors (and then no loads on them)? Outwards or inwards. Sorry, kept in place by the spandrels acting as belts around the tower. Inline, sideways? Sorry, no influence by floors there.

Main function of the floor, bolted on and hanging on the wall, was to walk on! Another function was to transmit horizontal wind loads on one wall to the opposite wall allowing the tower to sway, albeit steadily, sideways.

With all floors hanging on a wall the stress in the wall columns was 20% of yield all the way. Remove the floors and the stress was 1% of yield (only due to columns own weight). Buckling stress in both cases are >100% of yield, so nothing will happen.

Without floors WTCs were very strong cages. And cages of any size do not collapse due own weight. Read my article comparing WTC1,2 with a bird cage.

You are wrong. Why do you think pylons have stays?

A very high column can only stand as long as the vertical pressure vector falls within it's circumference. If it bends just a little bit, then the pressure comes outside the circumference and it bends more. This leads to collapse. Thus has nothing to do with buckling stress which presupposes that the force vector stays within the column.

Layman's explanation:

• Take a wooden broomstick.
• Saw about one foot of lenght off it.
• Take the one foot piece and put it on two bricks so just the ends are supported.
• Try to break it pushing down on the middle with your hand.

Odds are you can't.

Now repeat the procedure with the long piace of the broomstick. Much easier to break, right?

Now imagine a 100ft broomstick. Will it be able to carry its own weight?
Hardly.

Re. Bird cages:

A lot of people make the mistake of thinking that mechanical structures are freely scalable. They are not. Far from, in fact. The reason for this is that if you take a mechanical part, say, a steel girder and make it twice as big (scale it 2:1) then its width will be doubled, but its weight will be 8 times as big. This means that if you scale it sufficiently, it will buckle under its own weight. Likewise, a bird-cage is a quite rugged structure. But scale it 100:1, and it will collapse under its own weight.

Hans

 

[MRC_Hans]

1. The 33 000 tons are carried by 280+ columns. Average 118 tons/column

2. So 33 000 tons were shifted out of alignment with the columns below! Good. Actually 118 tons per column was shifted out of alignment. It means that these 118 tons will never again be applied on any column below! And it is valid for all columns.

So, you agree that the 33,000 tons are now no longer supported by the columns that used to support them. Good, we are making progress! Now, bereft of support, what will the 33,000 tons do? Hover??

3. <30% yield. Good industry standard!

So you concede that it was just standard margin. Thanks.

4. ?? How can a column below be impacted when the load above has shifted out of alignment?

Who says it was impacted directly? Where does the load go, now the column no longer supports it?

5. The upper part disintegrates before anything happens below the 'impact' zone. Very visible for WTC1! But see 4. How can a mass above impact a column below if it is not aligned?

I see no sign of that. Please provide support for that claim. Not that it matters. Disintegrated or not, it weights 33,000 tons. What carries the 33,000 tons?

6. See above. The beauty of a multi-column steel structure is that, if for any reason a mass above gets lose and starts to drop, it will not be aligned with the structure below = no global collapse. The weight drops beside the primary structure below!

Where does it go? If the primary structure below does not stop it, what does?

The wool bale analogy I only use when 'experts' talk about uniform density above and other nonsense. The weight of the wool bale is evidently transmitted to 280+ columns as packing ... but when the packing has shifted out of alignment with any support below ... the weight above drops like a bale of wool. Then the stresses in the packing is ZERO. And the wool will just drop by the solid structure below.

So you mean that it passes frictionlessly through the structure below or what exactly do you claim happens to it? There is 33,000 tons perched over the remains of the building, with nothing to support it. What do you claim happens to it?

PS Above replies all questions in your other comments. Just note that the initiation/impact zone is where the upper part allegedly free falls and vertically impacts the lower structure. Has nothing to do with a plane impacting same area 45-100 minutes earlier horizontally (another thread) which did not cause any global collapse of the intact structure below.

No, you did not answer all my questions, but never mind; I was never into Larsen Lists. Just answer the question here: What happened to the 33,000 unsupported tons of building?

Hans

 

[MRC_Hans]

It is always fascinating to see what gray ideas/questions the yellow greenhorns produce to support the red tape of NIST.

To start with - if an upper column is misaligned with a lower column a distance corresponding to the thickness of the plate of the columns after free fall (takes 0.5 seconds - not seen of course), the columns will never impact each other. In layman's terms the upper column misses the lower column.
I would then assume that 50% of the upper perimeter columns are outside the building - no floors there unless balconies were fitted (not seen on any videos) - and will meet no resistance. They should thus drop straight down.

So, the columns never impact! What we would expect then is that it is the bottom floor of the upper part that impacts the upper floor of the lower part.

No problem according NIST. Nothing happens! The upper block just drops another storey. Another floor then impacts the floor sandwich on the top of the lower structure. Nothing happens according NIST except that another floor impacts the tripple sandwich below. According NIST you can stack 11 floors on top of the uppermost floor of the lower structure and then that floor will fall down. The global collapse apparently starts.

Bfore that time 50% of the perimeter columns of the upper block are hanging in free air on the outside of two walls, and the remaining 50% perimeter columns have been punching holes in 11 floors below just inside the other walls. Never seen on any videos or Hollywood production. It is quite insane, what NIST proposes.

Very strange collapse, cowboy! Just watching the ears of your horse?

So we have this 33,000 tons of upper building, which, you apparantly agree, has been robbed of its support. Now, cowboy, what does it do:

1) Fly away to Kansas?

2) Hover and wait for the Marines?

3) Settle calmly on top of the remaining building, which, in spite of the supports being misaligned, carries its weight?

4) Jump to the side and land in the street below?

5) Crash down though the remaining building gathering momentum as more and more of the building is turned into falling junk?

Please pick only one. (Hint: The right answer is likely to be consistent with observed facts).

Hans

 

[MRC_Hans]

Apparently, between the bouts of talking with himself, heiwa has trouble understanding that .5g =/= 1.0g.
(i have him on ignore, so I wonder --is he arguing with himself, and if so, does he win those arguments?)

No, not even those. That would require a minimum of logical consistence.

Hans

 

[Heiwa]

This debate is going nowhere, so let me offer this:

I believe Heiwa's main point is that the Twin Towers were like very tall cages. And the more a cage structure is multiply connected horizontally as well as vertically, the more robust it gets. So how can a cage, or a part of a cage, collapse/crush another cage?

Now that's a fair question. But I think the answer to this question is that such a collapse can in fact happen if the cage unit-cells are weakly inter-connected, and this was probably the case for the Twin Towers. WTC 1 & 2 had relatively weak welds and relatively weak bolts. The buildings could literally "fall to pieces" if struck/stressed in a particular way.

Thus there is no need for explosives to explain the collapse of WTC 1 & 2. The structure of each tower was very sensitive (anywhere below the 100th floor) to local lateral stresses/impacts + heating rates. As a consequence, certain conditions are capable of triggering a self-propagating domino-effect/unzipping type of collapse, especially in the case of top-heavy buildings such as the Twin Towers.

I think the debate is very good when it is On Topic. I have got very valuable information. Photos, etc.

However, there are 1000's of photos of the collapses but unfortunately some are missing, i.e. those during the 0.5 seconds when the upper blocks start to free fall 3.7 meters - all columns failed - and then collide/impact with the structure below transmitting the upper block KE to the structure below. It is then the clock of collapse time should start.

But if there is no 'free fall' and no 'impact' then no gravity driven collapses can even be initiated and no collapse time clock will start. Any calculations about what happens after the alleged 'impact' become then pretty theoretical and, why not, meaningless?

So I would be grateful to see some photos when the upper blocks starts to free fall with the relevant columns missing, some photos a little after during free fall and some photos when the upper blocks collide/impact/strike with the lower structure.

That would settle the debate, I assume, that the collapses were actually started by gravity.

 

[Alferd_Packer]

oops, never mind

 

[Apollo20]

Heiwa:

There are plenty of photos/videos of WTC 1 AND WTC 2 showing the perimeter columns in the fire-affected impact zones bowing inwards. What do you think caused this bowing to occur? And do you think it contributed to collapse initiation?

 

[Alferd_Packer]

Heiwa, have you ever seen this formula before?

 

[NobbyNobbs]

I have last year written a paper about WTC1 for children that I copied Nist of course and then Nist changed opinion and suggested that 6-11 floors dropped down and caused global collapse. My paper has then been noted at JREF and there we are. No need to call anyone at Nist or contributing to Nist a fool. They are just working for the government.

You wrote a paper for kids? How on earth does that solve any problems?

Does anybody at JREF believe that a mass of uniform density 0.18, that collides with something, causes global collapse of something?

1. Go get a rowboat, and fill it with water until just before it sinks. The density of the rowboat is now only very slightly less than 1.

2. Now, row that boat out into the path of a battleship. (Bonus question: is the density of the battleship greater than or less than that of the rowboat?) See what happens to the rowboat.

3. After you swim back to shore, revise your theory about the twin towers.

 

[Myriad]

But if there is no 'free fall' and no 'impact' then no gravity driven collapses can even be initiated and no collapse time clock will start.

Heiwa, this is something you've been consistently wrong about all along. All that is needed to start a collapse is enough force to start things moving. The weight of the top of the tower is a force. When enough support members have been severed and weakened to no longer exert an upward force equal to the weight they have to support, f = ma will take over. The weight will start moving. That's collapse initiation. No impact (except, in this case, the impact of the airplane that caused support members to be severed) is required. No free-fall is required.

The conversion of gravitational potential energy into inelastic strain energy of the overloaded buckling columns, and into kinetic energy, happens as a result of the unbalanced force causing the mass to move. It doesn't have to happen "first."

Respectfully,
Myriad

 

[Newtons Bit]

Nice picture of WTC2 that proves my point 100%. No alignment at all of upper block with lower intact structure.

No, it completely disproves your point. You said it fell OUTSIDE. Stop trying to squirm away and admit that you made a small goof.

No free fall, no impact columns against columns. What you see on the photo is part of an unusual CD of WTC2. A second later the upper block disintegrates completely ... no load acting on it so you should wonder why! ... and long before it hits the ground. Where did the upper block of WTC2 go? It is supposed to drive the global collapse of the lower structure by falling straight down on it; impacts, crush front, etc.

This is complete B.S. The upper block does not disintegrate. It is heavily damaged, but so is the upper floors of the lower block, imagine! And then it travels inside of the tower and causing more damage to the floors below.

Read my article, the math is not too difficult, it is peer reviewed but have a try to find something wrong. Just copy/paste the erroneous part.

As a test I have hidden one minor error in my article.

From your paper

The major problem is that the authorities suggest that the top part, the upper block of WTC1 with mean density 0.18 tons/m3 above the alleged buckled columns in the initiation zone - no such damaged, buckled, columns have been retrieved from the rubble - drops free fall (!) as a rigid mass and releases potential energy, PE, and then destroys the weak steel structure below due to lack of strain energy, SE, there after an impact between the upper rigid part and the lower non-rigid part, while all videos of the collapse show that the upper block in fact telescopes into itself for 2-4 seconds, while the steel structure below is still intact! WTC2 is similar. The whole upper part of WTC2 tips over and disappears soon after. No free fall or impact occurs ... and cannot occur!

False. The upper block obviously falls at NEAR free-fall, otherwise we wouldn't have seen it fall. You can't say something didn't happen when there's video recording that it did.

Gravity is a force of attraction between any two objects. WTC1 and 2 consisted of many objects and, when WTC1 and 2 were intact and all objects were attached to each other, gravity resulted in compressive stresses in the primary load bearing columns that were <30% of the yield stress as will be shown in 3. below.

Inaccurate. You cannot take the entire cross-section of the tower and the entire load and say all columns were below a certain stress. This is because columns near severed and damaged columns are primary to resolving the loss of nearby strength. Furthermore, this ignores simple concepts such as a cantilever (ONE example) developing after a column is severed/damaged. This will multiply the vertical loads, easily overloading columns.

A floor is not a primary load bearing object. It just transmits its weight to the primary load bearing objects. It will also be clarified in 3. below.

False, the floors are necessary to provide bracing against buckling.

If you cut a primary load bearing vertical column in one location, it cannot transmit any load and the stress in it at the cut becomes zero. If you then cut the same object a bit away, the lose part will evidently drop out and fall down. If it is located in the wall, it is likely it drops down to the ground outside the structure. A core column may fall on a floor or down a lift shaft.

WTF. Obviously there is no stress in a column just above a cut. But the force that used to exist in that column has to be TRANSFERED SOMEWHERE ELSE. And it will not do that in a pure vertical fashion. You cannot understand the simple fact that the vertical forces will apply more than just a compressive force to the structure. This is BASIC statics.

In WTC1 and 2 we are told that 280+ primary load bearing vertical columns simultaneously failed in two locations in an initiation zone ... and disappeared allowing free fall. Fair enough! I do not believe it, because it is a crazy idea, but let's assume it anyway so this article can describe the madness.

Strawman. No one ever said that the columns failed simultaneously. Nor is this implied by the phyiscal evidence. The fact that both towers leaned noticeably during collapse shows that the towers collapsed linearly (roughly) from one side to another. This makes sense from how the tower actually resists core column failures.

Well, if the upper block above the initiation zone was then hanging in a crane and slowly lowered down and placed on the lower structure, the lower structure would evidently carry the upper block ... as before. The columns would again be stressed to <30% yield stress.

WTF? The upper block wasn't lowered, it collapsed. That's the entire point. Dynamic forces are much higher than static forces. That's why we design framing below corridors for 100psf live load, even though they will never expierence that amount of load statically. They will expierence something close to that dynamically.

These are the first six of your paragraphs. They are all complete crap. I'm just going to randomly select a few more.

How is the yield stress of steel affected by heat? In this writer's opinion it is not affected very much at about 500°C. This is confirmed by any fire test - the test chamber and what's in it never collapses due to the heat inside up to 1000°C. The heat inside is normally by kerosene set on fire.

Complete crap. I recommend you do a little research rather than relying on your own "opinion".

The total strain energy our wall and core columns and attached spandrels and floors can absorb is evidently the energy required to first strain them to 100% yield - the elastic strain energy - and second to buckle or rip them apart - the buckle or rupture strain energy. In order to rip a column apart, the stresses in the structure must exceed the rupture/break stress of the steel that is much higher than the yield or buckling stress.

Uneducated in engineering. The column will buckle before 100%, energy is absorbed when the column rotated about a plastic hinge (buckling), and THEN there will be a small amount of energy in rupture. Buckling is not the same rupture strain energy.

Reason why a steel building cannot collapse due to release of potential energy is, in simple terms, that the potential energy will mainly be applied to secondary structure - the floors - that will be overloaded and detached from the primary structure - the columns! The potential energy will then not be applied to the primary structure ... that will remain intact!

The floors are necessary to support the columns, otherwise they will just fall over and outwards (which is what happened) under smallish forces.

You also seem to be of the opinion that the entire upper block should disintegrate. But that doesn't make any sense. If the upper block can disintegrate from the striking the lower block, shouldn't the lower block (made of the same material, same craptacular uniform density measurement that you use) also be able to take damage from the upper block? You can't have it both ways.

Now then, you said something about calculations in your paper. The only thing I saw was inaccurately calculating weight and compressive stresses. Was there something else that I missed?

 

[Heiwa]

Heiwa, this is something you've been consistently wrong about all along. All that is needed to start a collapse is enough force to start things moving. The weight of the top of the tower is a force. When enough support members have been severed and weakened to no longer exert an upward force equal to the weight they have to support, f = ma will take over. The weight will start moving. That's collapse initiation. No impact (except, in this case, the impact of the airplane that caused support members to be severed) is required. No free-fall is required.

The conversion of gravitational potential energy into inelastic strain energy of the overloaded buckling columns, and into kinetic energy, happens as a result of the unbalanced force causing the mass to move. It doesn't have to happen "first."

Respectfully,
Myriad

Hm, enough force to start things moving. Only force available is gravity acting towards centre of earth. It acts on a mass above. The mass above is supported by 280 columns. Gravity compresses these columns <30% yield stress.
Columns are heated and failing (how?) one after the other so that the stresses in the remaining columns become 100% yield stress! OK. Due to Euler we know that they will not bucklebend then (no buckled columns from the initiation zone found), so they start to deform, compress plastically (none found either!). The mass moves down. When does this happen? Any photos? Due to gravity. Always equilibrium due to reaction forces in the lower structure columns equal to the gravity force acting on the mass above. Any PE released due to mass moving down is consumed to deform the supporting columns. Columns do not rupture in compression, as far as I am concerned.

So, why would the mass start to move down apart due plastic deformation in turn due to heating the columns? What about the reaction forces in the intact structure below?

Only way the reaction forces below cannot support the mass above is that the connecting columns are physically removed. Any photos of that?

And because the columns cannot be removed by gravity, there will be no collapse due to gravity.

So what removed the columns in the initiation zone? The outside columns are intact until they cannot be seen in the smoke/dust.

You haven't read my article, have you? Or done the model test, http://heiwaco.tripod.com/nist1.htm#6 ?

It would appear that the WTC1 upper block above the initiation zone implodes/telescopes into itself/disintegrates before gravity collapse starts below the initiation zone. It cannot have been caused by gravity. No photos of any failed columns there.

Whatever caused the upper block to implode/telescope into itself and produce smoke/dust to prevent further viewing prior collapse below initiation zone is probably also the cause of the destruction of the lower structure.

According Bazant and Seffen (read my paper) you need an intact, loose, rigid (all the time) upper block falling at a certain velocity on a structure to drive a gravity collapse of the latter, like an avalanche, until it runs out of energy.
During the complete process - avalanche - the lose KE must be applied uniformly on the structure (soil/snow) below. Uniform density you know is required.

But there is no intact, loose, rigid upper block at any velocity in the WTCs to drive a gravity collapse. And no uniform density.

The WTCs are nice examples of high tech CD. I wonder how the perpetrators did it! Clever to blame gravity for it using university profs as useful idiots.

Kind regards

Heiwa

 

[Heiwa]

Heiwa:

There are plenty of photos/videos of WTC 1 AND WTC 2 showing the perimeter columns in the fire-affected impact zones bowing inwards. What do you think caused this bowing to occur? And do you think it contributed to collapse initiation?

Any alleged deformations prior start of collapse is of little interest. Pls provide photos of the perimeter columns taken after the upper block started to move and before the lowest floor of the upper block reaches the uppermost floor of the intact structure 3.8 meters below. Time for this initial 'collapse' is 0.5 seconds assuming free fall acceleration = several frames on any video. Longer if the columns are assumed connected to the upper block and lower structure and fails in one way or another but offering resistance = many more frames of any video.

Thanks for your assistance. I will publish any of these photos on my web site.

 

[Architect]

Heiwa

It's time to come clean, mate.

You haven't *actually* studied building structures, have you?

Tell the truth. We'll respect you for it.

 

[stateofgrace]

Hiewa, I have been following this thread and I must say I do find your theory somewhat " out there" but hey you are entitled it.

From what I gather you seem to base your entire agrument on your belief that the upper portion of the tower did not impact the lower portion.It seems you are agruing that the entire upper portion above the impact zone completly disintegrates before any such an impact took take.

OK, it as been pointed out to you that the "upper block" weighted in at some 30,000 tons. Can you please tell me how much explosive power would be needed to produce such a complete disintegration?

Equally so can you also tell me, once the complete disintegation of the upper portion has happened how much explosives would be needed to stage the rest of the top down demolision?

Thank you.

 

[NobbyNobbs]

I'm not sure I'm following here, but the impression I get is that Heiwa believes that the upper portion of the building, along with all its support beams and such, was moved two feet to the right, and then came straight down.

Have I got it right?

 

[Apollo20]

Heiwa:

Sorry to be pedantic about this but the free fall time for 3.8 meters is not 0.5 seconds.

s = 1/2 a.t^2

3.8 = 1/2. 9.81 . t^2

t^2 = 0.7747

t = 0.8802 seconds

Also I believe the floor height was closer to 3.7 meters so a better value for the free fall time of a WTC floor would be t = 0.8685 seconds

Anyway, the free fall time to which you refer is closer to one second than half a second.

Regardless of this, the behavior of the north face of WTC 1 at the 98th floor is obscured very quickly after the first movement of the roof line.

Unfortunately all the "action" during the first few seconds of the collapse of WTC 1 was at the south face where we know there was pre-collapse bowing.

Please explain this pre-collapse bowing and/or explain why "any alleged deformations prior (to the) start of collapse are of little interest."

 

[Dave Rogers]

There are plenty of photos/videos of WTC 1 AND WTC 2 showing the perimeter columns in the fire-affected impact zones bowing inwards. What do you think caused this bowing to occur? And do you think it contributed to collapse initiation?

Heiwa answered this one a long time ago. He said that this bowing was highly unlikely, therefore the photographs must have been faked.

Dave