Claim: Jim Hoffman's "9/11 progressive collapse challenge" can't be met

[econ41]

At some risk of complicating things:

Just a quick point of personal privilege: I'm not debating. I'm trying to understand your understanding of the exterior shells of the Twin Towers. I had always thought they were entirely self-supporting. And I didn't realize how committed @Mick West was to the idea that they weren't "shells" so much as "skins", unable to maintain rigidity without a "skeleton" inside the building. I thought the design concept was that the facade was an "exoskeleton".

Yes - change "debating" to "discussion". Yes the facade most definitely was not an "exoskeleton". And it also wasn't a "skin" in the non-structural sense. It was a definite contributor to the structural integrity and strength. The point I think is now clearer is that those lay-person explanations from Wikipedia et simile as per your next comment are misleading:

If I understand this correctly, then there is indeed a debate or dispute between truthers and debunkers and I have (unknowingly) been on the "truther side" of it. Until this discussion, I thought everyone believed that the facade carried "all the lateral loads and most of the gravity loads" (quoting something from memory, probably in the Wikipedia article or its sources). This has been very illuminating.

The bolded bit is definitely misleading as you now comprehend. And we can go further with "illuminating" discussion if you wish.

But, to repeat, I don't have a position on this (because I didn't know I needed one). At this point, I'm still trying to make up my mind.

I think several of us are better understanding where we are each coming from.

 

[Thomas B]

Jeffrey Orling contributed some numbers and I think he is right. I have ZERO doubt that (b) is impossible.

Can you or @Jeffrey Orling work the numbers for my paper tower? I'm using 90 g/m2 paper, but I could probably find even weaker material. How big a sheet of 4:3 paper do I need to make a tower that will crush itself (without any floors or other load)? Or, more simply, what's the maximum height of my 6:1 paper tower?

[EDIT: I said I could find "even weaker material", but it occurs to me that there's also a weight issue. So I could also find heavier material if that helps. But that would in most cases increase strength, I suspect. I suppose this problem is familiar to engineers. Anyway: you're free to suggest different paper. I just need to know the length of the sheet (since that's also the height of the tower.)]

 

[Gamolon]

View attachment 43594
This one stands up also when I take out the floors (every 7.5 cm). But I could probably stack four of them on top of each other without causing them to collapse.

[EDIT: It's actually 41 cm tall. It's a page torn from a croquis pad with a coil binding. It turns out the pad is 42 cm, the page you tear off is 41 cm. Just in case you're doing the math at home.] [EDIT: I updated the picture.]

[EDIT: This one has about the right the aspect ratio for our purposes, almost 6:1. But all this is of course quite arbitrary since the strength of the materials haven't been chosen with any particular care. It's just the grade of paper that happened to be in the pad, and I used the dimensions I could get just by folding. I'm hoping I can push the materials to their breaking point by scaling up, or maybe finding some cheaper paper. The challenge will be getting it to be "strong" in its normal configuration and yet vulnerable to top-down collapse when properly loaded and wounded.]

Thomas, is this the same model I suggested trying in the post just above? Taking the four sheets of paper you taped together to form a square tube and then creating four more of those same cubes and taping them together, one on top of the other.

This was to see if the constructed tube would stand on it's own.

 

[Thomas B]

The bolded bit is definitely misleading as you now comprehend. And we can go further with "illuminating" discussion if you wish.

Again, just to be clear: I don't understand it yet. What I have found "illuminating" is that this disagreement exists.

The received view among truthers is that the shell/core structure is basically one skyscraper inside another, with floors suspended between them. They would probably easily grant that the structures become more rigid (i.e., will sway less) with the floors in place. But they would not suspect that the buildings fall apart altogether if you remove the floor joists.

Until yesterday, I thought this was completely uncontroversial. I still don't really understand your view of it -- that is, I don't understand why buildings would be built that way. And it seems to be received view around here. Lots to take in all at once.

 

[Mick West]

huh. I admit i never did grasp (after 5 years of reading MB 911 threads) how roosd is really different from the term pancaking. So now that i know they aren't different i'm going to have to agree with NoParty on this one. probably easier for laymen if you just call it Consecutive Floor Collapse or something.

I generally refer to the progression mechanism as "floor stripping". It only captures a part of the mechanism, albeit a very important part.

But I see from @Thomas B that this too can lead to confusion, with now an excessive focus on large-scale buckling of the exterior (which is actually a key part of the collapse of WTC7, but less so on the Towers.

The sad part here is that, I think, most structural engineers familiar with tall buildings would be rather bemused that this is even some kind of debate. The towers were carefully constructed with safety margins to withstand the static load, plus imaginable dynamic loads (mostly wind). After the initiation, the progression of the collapse was a series of rapidly increasing dynamic loads that vastly exceeded the design parameters in a chaotic variety of directions.

 

[Mick West]

The received view among truthers is that the shell/core structure is basically one skyscraper inside another, with floors suspended between them.

Is it? Where have you seen this?

I really doubt even Richard Gage thinks this. But I'd be interested if this is the case.

 

[Thomas B]

Thomas, is this the same model I suggested trying in the post just above?

Sort of. It only has one seam (the far corner in the picture). I made it by folding a single piece of paper instead of joining four narrow strips with tape. The folds are equivalent to a perfect job of joining the seam with tape (I'm getting better and better at that with each iteration). Otherwise, yes, I'm trying to build a paper tower with mutually bracing sides.

Did I completely misunderstand your suggestion?

 

[Thomas B]

Is it? Where have you seen this?

I really doubt even Richard Gage thinks this. But I'd be interested if this is the case.

Curioser and curioser! as Alice said. All these years I've been sure that the truther position was grounded in a radical overestimation of the strength of the towers in their normal state, both the core and the shell. Though he's a bit passé, I guess, in keeping with OP for this thread, Jim Hoffman's understanding of the buildings would be one example:

1 and 2 World Trade Center used the so-called tube within a tube architecture, in which closely-spaced external columns form the building's perimeter walls, and a dense bundle of columns forms its core. Tall buildings have to resist primarily two kinds of forces: lateral loading (horizontal force) due mainly to the wind, and gravity loading (downward force) due to the building's weight. The tube within a tube design uses a specially reinforced perimeter wall to resist all lateral loading and some of the gravity loading, and a heavily reinforced central core to resist the bulk of the gravity loading. The floors and hat truss completed the structure, spanning the ring of space between the perimeter wall and the core, and transmitting lateral forces between those structures.

Now that I notice it, I can see he also grants that the floors "completed the structure" and that they "transmitted lateral forces". But I really never suspected he'd think the perimeter would collapse without them. I still don't think that's what he means by that. But I've got something to think/read some more about, I guess. (I was wrong about the perimeter being thought to carry "most of the gravity loads". It also makes more sense that that would be the core's job.)

 

[Gamolon]

Sort of. It only has one seam (the far corner in the picture). I made it by folding a single piece of paper instead of joining four narrow strips with tape. The folds are equivalent to a perfect job of joining the seam with tape (I'm getting better and better at that with each iteration). Otherwise, yes, I'm trying to build a paper tower with mutually bracing sides.

Did I completely misunderstand your suggestion?

I believe so. You're answer to Jeffery Orling's example of a sheet of paper buckling post was that the sheet of paper buckled on it's own. But then you taped four of those sheets together at right angles and proclaimed that they stood on their own which you seemed to use as proof that the perimeter facade would have stood on it's own.

I asked you to construct four more of those same tubes, by using the same method you did for the first one. By taping four sheets of paper together at right angles and then taping them together, one on top of each other. That would be of five of them in total.

 

[Thomas B]

I asked you to construct four more of those same tubes, by using the same method you did for the first one. By taping four sheets of paper together at right angles and then taping them together, one on top of each other. That would be of five of them in total.

I did understand that, but I suppose I took the easier route to [nearly] the same aspect ratio. Your idea would take a lot of careful taping. Are you suggesting that a 150 x 20 x 20 cm paper tower (i.e., folding a tower out of sheet of paper 150 x 80 cm) would collapse under its own weight?

 

[Mick West]

From the original 2002 FEMA report:

FEMA403 -- Chapter 2

2.2.1.5 Progression of Collapse [WTC1]

Construction of WTC 1 resulted in the storage of more than 4x1011 joules of potential energy over the 1,368-foot height of the structure. Of this, approximately 8x109 joules of potential energy were stored in the upper part of the structure, above the impact floors, relative to the lowest point of impact. Once collapse initiated, much of this potential energy was rapidly converted into kinetic energy. As the large mass of the collapsing floors above accelerated and impacted on the floors below, it caused an immediate progressive series of floor failures, punching each in turn onto the floor below, accelerating as the sequence progressed. As the floors collapsed, this left tall freestanding portions of the exterior wall and possibly central core columns. As the unsupported height of these freestanding exterior wall elements increased, they buckled at the bolted column splice connections, and also collapsed. Perimeter walls of the building seem to have peeled off and fallen directly away from the building face, while portions of the core fell in a somewhat random manner. The perimeter walls broke apart at the bolted connections, allowing individual prefabricated units that formed the wall or, in some cases, large assemblies of these units to fall to the street and onto neighboring buildings below.

FEMA403 -- Chapter 2

2.2.2.6 Progression of Collapse [WTC2]

As in WTC 1, a very large quantity of potential energy was stored in the building, during its construction. Once collapse initiated, much of this energy was rapidly released and converted into kinetic energy, in the form of the rapidly accelerating mass of the structure above the aircraft impact zone. The impact of this rapidly moving mass on the lower structure caused a wide range of structural failures in the floors directly at and below the aircraft impact zone, in turn causing failure of these floors. As additional floor plates failed, the mass associated with each of these floors joined that of the tower above the impact area, increasing the destructive energy on the floors immediately below. This initiated a chain of progressive failures that resulted in the total collapse of the building.

Something of an aside, I think a contributing factor to the misunderstandings around the collapse is fact that the FEMA report and the later NIST reports were distributed as protected PDF files, with copying disabled. This made it harder (especially in the 2000s) to share useful portions, leading to a more general lack of unfamiliarity with the reports.

 

[Jeffrey Orling]

I would like to inject the fact that the floors were a composite of concrete, re bar and open web steel trusses... the slabs were no ON the trusses the trusses were embedded into the concrete. The entire composite acted as a rigid plate which rested on steel angles welded to both the perimeter steel and the belt girders which encircled the core. The belt girders had cantilevers connecting it to the 24 core columns. The short cantilevers are called beam stubs Floor system rested on steel angles.

It is instructive to know how the towers were built which was novel at the time. I prepared the drawings below to help me understand the structure. without some detailed understanding of the structure it is impossible to understand how they collapsed as they did.

Key aspects of the construction:

all floors (except mechanical floors) were identical in structural design
each floor was constructed from a prefabricated "panel" which was made from 2 trusses joists and corrugated steel decking connecting the trusses.
These panels were hoisted into place and then bolted down to the steel angled at the perimeter and at the belt girder.

All core columns were 3 stories tall. The top and bottom did not align with a floor plate. The floors were connected at approximately 4', 16, 28' from the bottom. All facade "columns" were prefabricated into panels with 3 columns and 3 spandrel beams.. hoisted into place and bolted together with splice plates and bolts in end plates of the columns. Facade panels were staggered vertically.

All steel columns were thinnest at the top and were thick as the loads aggregated.

The strongest core columns were the 24 columns on its perimeter with the 4 corner columns being the strongest.

So the floors were identical over the entire height... but the columns were massively thick steel plate at the bottom thinning to 1/4" thick at the top.
The design was developed to save enormous erection time... with little welding and mostly bolting.

It should be noted that the floor systems are connected to the sides of the columns... and acted as footprint sized rigid rectangular donuts connected to the steel frame ONLY the truss locations

The floors in the core were more traditional. There were girders and beams with metal decking and concrete slabs. All the concrete and the re bar in the floors was installed in the field, of course.

The 4 mechanical floors had conventional beam and slab construction... and were designed for the heavier loads of mechanical equipment.

++++

Traditional steel high rise structures had been "stick built" from the ground up... (similar to the core of the twin towers) with a column grid about 25' (varied). Twin towers had no columns in the office use spaces outside the core. The core contained bathrooms, plumbing. electrical and mechanical risers and of course the elevators.

These are graphics and no complex calculations are needed to understand the stucture.

 

[Gamolon]

I did understand that, but I suppose I took the easier route to [nearly] the same aspect ratio. Your idea would take a lot of careful taping. Are you suggesting that a 150 x 20 x 20 cm paper tower (i.e., folding a tower out of sheet of paper 150 x 80 cm) would collapse under its own weight?

No.

I think we're using the term "sheet of paper" to mean different things.

"Sheet of paper" to me is 8.5" x 11" inch piece of paper.

You would need 20 sheets of this paper.

 

[Thomas B]

"As the floors collapsed, this left tall freestanding portions of the exterior wall and possibly central core columns. As the unsupported height of these freestanding exterior wall elements increased, they buckled at the bolted column splice connections, and also collapsed." (FEMA)

Again, I'm new to thinking about this specific issue, but wasn't the argument here that the longer the "unsupported height" of the perimeter columns was, the more likely they to buckle under the weight of the floors above, and especially the dynamic load they constituted after they began moving? I think there was indeed some limit (I've read it somewhere) to how many floors you'd be able to remove under how many floors (i.e., a certain mass) above. (This was important to know because some tenants, especially in building 7, wanted high ceilings.) But if you remove all the floors, we're back to the lateral loads only, "all" of which (I thought) they were designed to resist.

 

[Jeffrey Orling]

Can you or @Jeffrey Orling work the numbers for my paper tower? I'm using 90 g/m2 paper, but I could probably find even weaker material. How big a sheet of 4:3 paper do I need to make a tower that will crush itself (without any floors or other load)? Or, more simply, what's the maximum height of my 6:1 paper tower?
]

First of all you would need "tapered" paper... because the towers has much thicker / stronger structure at the bottom becoming thinner / less strong toward the top.

the first 3 floor columns had plates that were 3" thick (core and facade) and at the top the were 1/4" thick. Yet all floors were identical "structures" except the mech floors.

The 4 mech floors are significant structurally in that they were very rigid "blocks" adding much stiffness to the tube.

 

[Thomas B]

You would need 20 sheets of this paper.

But the first thing I would do is to tape them all together along their edges to form one big sheet of paper, 34" x 55". [Ooops, had to edit my math there.] Then I'd fold along the long seams.

 

[Thomas B]

First of all you would need "tapered" paper... because the towers has much thicker / stronger structure at the bottom becoming thinner / less strong toward the top.

This may become necessary in my final model, I will grant that. I might layer the paper in the lower sections. But that would make the resulting tower much, much, taller in this case where it doesn't have any load but itself to carry.

 

[Gamolon]

But the first thing I would do is to tape them all together along their edges to form one big sheet of paper, 34" x 55". [Ooops, had to edit my math there.] Then I'd fold along the long seams.

Yes.

 

[Thomas B]

Yes.

And you think a 55" by 8.5" square paper tube (folded out of a 55" by 34" sheet of paper and taped along the seam) wouldn't be able to stand on its end?

 

[Thomas B]

Question for @econ41 and @Jeffrey Orling:

Take any individual perimeter column, running the whole length of a WTC tower, completely unsupported laterally along its length. Treat it as pinned at the top and fixed at the bottom. Will it buckle under its own weight? If not, what's the maximum distance it can bend at the middle before it does?

 

[Gamolon]

And you think a 55" by 8.5" square paper tube (folded out of a 55" by 34" sheet of paper and taped along the seam) wouldn't be able to stand on its end?

That's what I'm thinking. I'll try it also. We'll compare notes when we're done.

 

[Thomas B]

That's what I'm thinking. I'll try it also. We'll compare notes when we're done.

I'm so confident (on the basis of my partial experiments) that I'm not sure I'll bother. (Consider: everything will depend on the load on the bottom section of four sheets, right? So build the lower section and just put 16 pieces of paper flat on top. It's not going to collapse.) If you do try this (i.e., actually build the tower) and get a different result, though, I'll definitely try to replicate it.

 

[Gamolon]

I'm so confident (on the basis of my partial experiments) that I'm not sure I'll bother. (Consider: everything will depend on the load on the bottom section of four sheets, right? So build the lower section and just put 16 pieces of paper flat on top. It's not going to collapse.) If you do try this (i.e., actually build the tower) and get a different result, though, I'll definitely try to replicate it.

Here's my paper tower. I'm holding it up while it touches the floor.

Here's my paper tower after taking my hand away.

That tower was only using four of the five "cubes". I used two small pieces of Scotch tape at each connecting edge of the sheets of paper.

 

[deirdre]

Yes, easily. With the floors in place, the tower can support at least ten batteries on the top.

that's a roof, not a floor. but carry on.

 

[Jeffrey Orling]

Question for @econ41 and @Jeffrey Orling:

Take any individual perimeter column, running the whole length of a WTC tower, completely unsupported laterally along its length. Treat it as pinned at the top and fixed at the bottom. Will it buckle under its own weight? If not, what's the maximum distance it can bend at the middle before it does?

Absolutely would self buckle. Look at the explanation of the collapse of the spire.. col 501 the strongest column in the building.

 

[Jeffrey Orling]

A key point to understand about Euler buckling is that the weakest axis governs.. so in the spire example you can see that the short axis would promote euler buckling. In the facade... even if you were to consider a entire side as "plate" its shorter axis... 14" would govern... So the floors BRACE the short axis and without the floors it WOULD buckle even as a single plane 200' x 1400' x 14"

 

[deirdre]

I'm so confident (on the basis of my partial experiments) that I'm not sure I'll bother. (Consider: everything will depend on the load on the bottom section of four sheets, right? So build the lower section and just put 16 pieces of paper flat on top. It's not going to collapse.) If you do try this (i.e., actually build the tower) and get a different result, though, I'll definitely try to replicate it.

i dont understand at all what you are trying to do, but i have 80 inches of paper left on my roll. it will take a day of book flattening to "kill the roll curve", but i can fold it in 4 and tape one corner to make a tower tomorrow or later today. each building side would be 12 inches unless i cut it (so likely not to tt scale). i can tell already it wont hold much weight if i tube it tomorrow..

(im not willing to cut it for this experiment as i use it big for painting sketches etc... but you can buy rolls of paper for like 8 bucks. here is rosin paper for 14$, rosin paper is very thick made for walking on https://www.amazon.com/Trimaco-3514...=1&keywords=rosin+paper&qid=1616944397&sr=8-2 )

 

[Thomas B]

that's a roof, not a floor. but carry on.

I meant there are five floors inside that particular tower providing lateral support.

 

[Thomas B]

I used two small pieces of Scotch tape at each connecting edge of the sheets of paper.

Well, I promised, so I'm going to have to put a tower where my mouth is. I don't have time tonight, but I can already tell you I'm going to be using more tape. I don't know how significant you think that is.

 

[Thomas B]

i can tell already it wont hold much weight if i tube it tomorrow

Without the floors in place it will indeed not hold much weight. The question we're exploring is whether it will hold its own weight.

This actually helps me understand what we're talking about, so thanks. @Mick West (and everyone) is of course right that without the lateral bracing of the floors the perimeter would not be able to support the weight of the the floors. I definitely recognize the importance of lateral bracing and how it increases the effect[ive] strength of a column. What puzzled me was the idea that the perimeter wouldn't even be able to support its own weight -- i.e., without any load on it at all.

Absolutely would self buckle.

This, for example, I still don't understand. If, say, two [or 240] columns indivdually can't support their own weight, how does loading them with 100 floors weighing millions of pounds between them make them stand up?

 

[Mick West]

Again, I'm new to thinking about this specific issue, but wasn't the argument here that the longer the "unsupported height" of the perimeter columns was, the more likely they to buckle under the weight of the floors above, and especially the dynamic load they constituted after they began moving?

Columns, boradly speaking, can fail in two ways: compressive failure (being squashed vertically), or buckling failure. Illustrated below.

A column buckling is a situation of dynamic instability, where once it starts, the buckling weakens the column more, leading to rapidly increasing buckling. The yellow can above will no longer support a 100lb person in any way, whereas an intact can could easily do this.

But the WTC columns didn't even fail like this. They failed at the joints. Imagine two cans stacked one upon the other, lightly taped, with a load applied to the top. Imagine extending this to 3, 4, or 5 cans. It's obvious that it's an unstable structure.

But mathematically, there no difference between 1 can and 5 cans in terms of vertical load carrying. The buckling has to come from something other than simple numbers. That something is a combination of it not being perfectly vertically aligned, and dynamic loads, specifically dynamic lateral loads. If something is pushing on the column assembly from the side then that introduces variations in the vertical load paths that can lead to buckling. Large forces = more effect.

With the collapse of the WTC towers, there was a chaotic combination of various things that all need to be considered.

1. The stripping of floor leaving lengths of column assemblies unbraced (or significantly less braced)
2. Wildly varying, and increasingly large, vertical dynamic forces from the falling mass.
3. Wildly varying, and increasingly large, lateral dynamic forces

These things were not even close to being within the design specification of the column assembles. So they popped apart, largely at the connections where they were welded or bolted together. So most of the columns you see in the debris pile are straight.

 

[Jeffrey Orling]

Without the floors in place it will indeed not hold much weight. The question we're exploring is whether it will hold its own weight.

This actually helps me understand what we're talking about, so thanks. @Mick West (and everyone) is of course right that without the lateral bracing of the floors the perimeter would not be able to support the weight of the the floors. I definitely recognize the importance of lateral bracing and how it increases the effect[ive] strength of a column. What puzzled me was the idea that the perimeter wouldn't even be able to support its own weight -- i.e., without any load on it at all.


This, for example, I still don't understand. If, say, two [or 240] columns indivdually can't support their own weight, how does loading them with 100 floors weighing millions of pounds between them make them stand up?

Each material has a different set of characteristics or attributes.. for example, for metals the temperature at which they melt. One of the attributes is strength of "load capacity" per unit area. Practically steel is quite efficient... strong... but as you know from the twin towers.. the columns carrying more load have greater cross section... see the graphic above. When a column is loaded the forces are "resolved" and there are horizontal forces.... If you take a wood stud and keep increasing the load it begins to bow. The weight on the top shortens the effective length and the stud bow. Eventually the stud will buckle.
Now if you stack on stud on top of another of the same cross section... the weight on the lowest stud gets larger and larger with each stud added until the bottom bows and then buckles. As a single tall column buckles from euler forces. Column designs are for column the slenderness ratios of less than 150. Short columns have slenderness ratios of less than 40 for steel, less than 9.5 for aluminum T6 and less than 11 for wood.
Bracing reduces the "effective" length... to braced tall columns act structurally like shorter columns.

 

[Jeffrey Orling]

These things were not even close to being within the design specification of the column assembles. So they popped apart, largely at the connections where they were welded or bolted together. So most of the columns you see in the debris pile are straight.

The connections are much weaker laterally and effectively simply kept the columns in axial alignment. In fact. in the towers the column to column connects were not restrained from lateral movement except for relatively thin splice plates or bolts. No beams / floor framing at the columns connections!

 

[Thomas B]

Columns, boradly speaking, can fail in two ways: compressive failure (being squashed vertically), or buckling failure.

I just want to be clear that I understand this, and what (I think) we're talking about is whether the exterior shell, without any of the loading of the floors, would buckle itself, thus being squashed by its own weight or would fail by "not being perfectly vertically aligned".

The can is a good example of what I'm thinking of. How tall would the can have to be to crush or buckle itself? How would it fail if you added no additional loads?

[Edit: or how many cans would you need to glue on top of each other before it's likely that, without any other loading, including laterally, they would collapse?]

 

[Thomas B]

...the columns carrying more load have greater cross section... see the graphic above. When a column is loaded the forces

I'm asking about a completely unloaded column.

Suppose you have four columns, none of which can support their own weight if placed perpendicular to the ground. How can they be combined to support the non-zero (or even zero!) dead weight of any number of floors?

The image I have of what you're telling me is: you've got four shoelaces that somehow become columns because you connect them to the corners of floors. It makes no sense to me.

 

[Jeffrey Orling]

I just want to be clear that I understand this, and what (I think) we're talking about is whether the exterior shell, without any of the loading of the floors, would buckle itself, thus being squashed by its own weight or would fail by "not being perfectly vertically aligned".

The can is a good example of what I'm thinking of. How tall would the can have to be to crush or buckle itself? How would it fail if you added no additional loads?

[Edit: or how many cans would you need to glue on top of each other before it's likely that, without any other loading, including laterally, they would collapse?]

So look at the table for S/R ratios for aluminum... a can is round so there is no minor or major axis... looks like a stack 66 cans would self buckle.

 

[deirdre]

I just want to be clear that I understand this, and what (I think) we're talking about is whether the exterior shell, without any of the loading of the floors, would buckle itself, thus being squashed by its own weight or would fail by "not being perfectly vertically aligned".

The can is a good example of what I'm thinking of. How tall would the can have to be to crush or buckle itself? How would it fail if you added no additional loads?

[Edit: or how many cans would you need to glue on top of each other before it's likely that, without any other loading, including laterally, they would collapse?]

what about using your idea of straws. the upshot is you can burn the bottoms and solder them together with the melted plastic. (i'd do it in a garage though or make sure you have a fan blowing out an open window or youll get high pretty quick.) You can secure the bottom with a glob of melted candle wax. ???

 

[Thomas B]

looks like a stack 66 cans would self buckle.

I realize you're making an empirical statement so it's going to come down to an experiment. But doesn't that seem wrong to you intuitively? Imagine 7 stacks of ten empty beer cans standing side by side -- seven 4-foot aluminum towers. Look at them with your mind's eye. Feel their weight in your mind. Now imagine putting them all on top of each other. One big tower of 70 beer cans glued together, 28 feet tall. Do you expect them to collapse? With no additional loading, whether vertical or lateral?

[Edit: the tower would weigh just over 2 pounds. But an aluminum can can "easily" "support a 100lb person".]

 

[Jeffrey Orling]

I realize you're making an empirical statement so it's going to come down to an experiment. But doesn't that seem wrong to you intuitively? Imagine 7 stacks of ten empty beer cans standing side by side -- seven 4-foot aluminum towers. Look at them with your mind's eye. Feel their weight in your mind. Now imagine putting them all on top of each other. One big tower of 70 beer cans glued together, 28 feet tall. Do you expect them to collapse? With no additional loading, whether vertical or lateral?

[Edit: the tower would weigh just over 2 pounds. But an aluminum can can "easily" "support a 100lb person".]

But a stack of them can't! It may be counter intuitive... but greater slenderness ratios are weaker!

 

[Thomas B]

But a stack of them can't! It may be counter intuitive... but greater slenderness ratios are weaker!

We must be misunderstanding each other. Which of the following statements do you disagree with:

1. A single empty beer can can support a 100 lb person.
2. 70 empty beer cans weigh a little over two pounds altogether.
3. A single empty beer can support a three-pound block of solid aluminum.
4. A tower of 10 empty beer cans will remain standing.
5. A tower of 20 empty beer cans will remain standing.
6. A tower of 30 empty beer cans will remain standing.
7. A tower of 40 empty beer cans will remain standing.
8. A tower of 50 empty beer cans will remain standing.
9. A tower of 60 empty beer cans will remain standing.
10. A tower of 70 empty beer cans will remain standing.