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

[Thomas B]

1. What does 80% of the mass of the towers being below the level of weakening have to do with anything?

That's roughly what happened on 9/11. I just want to make sure that the model can't be rejected as easily as it would be if I dropped, say, a single car battery on top of an otherwise unloaded paper tube.

2. You think the top floor of the remaining 80% of the structure was designed to withstand the impact of the upper 20%

No, I expect my model to collapse to the ground. That's the point of building it -- to reproduce a top-down progressive collapse roughly within the terms of Hoffman's challenge, using simple materials like paper, cardboard, and tape.

3. Do cardboard floors effectively replicate how concrete floors would behave when impacted?

They're not the concrete but the trusses. (Corrugated cardboard is essentially a truss structure.) They will bend slightly when impacted, and the force of the impact will detach them from the walls, to which they have been taped.

The concrete in the system is mainly represented by the batteries, though any recognizably massive household object will do as a unit load. (I want to be able to say, e.g., that its normal state is 2 AA batteries per floor, but that it has been tested with 4 batteries per floor and survived.) This is a clear limitation of the model, but one that I'm willing to accept: the energy to pulverize the concrete will not be demonstrated. Obviously the batteries are much stronger than concrete at this scale.

 

[deirdre]

No, I expect my model to collapse to the ground.

how can a solid tube collapse to the ground? it can't, it can only fall over.

when engineers say the mesh exterior couldnt stand on it's own with the slightest wind etc, they arent suggesting it would collapse the same way the Twins collapsed. edit add: note, they arent saying it would fall over or bend in half like a solid paper tower either)

 

[Gamolon]

That's roughly what happened on 9/11. I just want to make sure that the model can't be rejected as easily as it would be if I dropped, say, a single car battery on top of an otherwise unloaded paper tube.

No, I expect my model to collapse to the ground. That's the point of building it -- to reproduce a top-down progressive collapse roughly within the terms of Hoffman's challenge, using simple materials like paper, cardboard, and tape.

They're not the concrete but the trusses. (Corrugated cardboard is essentially a truss structure.) They will bend slightly when impacted, and the force of the impact will detach them from the walls, to which they have been taped.

The concrete in the system is mainly represented by the batteries, though any recognizably massive household object will do as a unit load. (I want to be able to say, e.g., that its normal state is 2 AA batteries per floor, but that it has been tested with 4 batteries per floor and survived.) This is a clear limitation of the model, but one that I'm willing to accept: the energy to pulverize the concrete will not be demonstrated. Obviously the batteries are much stronger than concrete at this scale.

Question.

Do you think smashing two Tyco HO scale locomotives into one another head on would give me accurate damage results to apply to a real life locomotive collision?

 

[Thomas B]

Do you think smashing two Tyco HO scale locomotives into one another head on would give me accurate damage results to apply to a real life locomotive collision?

No.

Nor is my model a WTC pewter gift shop statue of the buildings. It is specifically designed to scale down the forces involved.

If someone claimed that it is physically impossible for two identical locomotives to destroy each other in a head-to-head collision, we could, in fact, illustrate the physical principles by building two paper locomotives. But, as I think you're hinting, using the Tyco locomotives wouldn't work.

 

[Thomas B]

how can a solid tube collapse to the ground?

Solid? Cube?

 

[Gamolon]

No.

Nor is my model a WTC pewter gift shop statue of the buildings. It is specifically designed to scale down the forces involved.

Is it specifically designed to scale down the forces involved?

How do you know this? Let's take the floor connections for example. How have you determined that the taped connections are a properly scaled down version of the actual truss seats that were used?

How do you know that the taped edges/seams of the paper are properly scaled?

How does using cardboard as the floors properly scale with actual load bearing properties of the actual concrete floors and their trusses?

That's just to name a few questions.

If someone claimed that it is physically impossible for two identical locomotives to destroy each other in a head-to-head collision, we could, in fact, illustrate the physical principles by building two paper locomotives. But, as I think you're hinting, using the Tyco locomotives wouldn't work.

How would building two locomotives out of paper properly illustrate the physical principles of a head on collision between two real locomotives?

 

[Thomas B]

No, I expect my model to collapse to the ground. That's the point of building it -- to reproduce a top-down progressive collapse roughly within the terms of Hoffman's challenge, using simple materials like paper, cardboard, and tape.

"Gravity doesn't scale well," it is said. And I understand this. So it's possible that my model will fail (i.e., won't collapse) at the scales I'm working with. (My model is 15" and I think I'd give up at about 30". Although @deirdre's 80" effort is inspiring and I may buy a roll of paper like that one day. If that doesn't work, I won't go any higher.) But in that case I hope I will have learned enough about parts of the process to say how tall a paper model would need to be, and why that is, to understand how these structural principles ultimately scale up to become the WTC on 9/11.

 

[Thomas B]

How would building two locomotives out of paper properly illustrate the physical principles of a head on collision between two real locomotives?

The two paper trains will destroy each other as real trains would. The two Tyco trains will "confirm" the "trainer's" "conspiracy theory" that the trains can't harm each other structurally, only "bounce" off each other. That's because at their scale they're just way too strong for the forces involved.

 

[Gamolon]

The two paper trains will destroy each other as real trains would.

Wait... What? You honestly think that building two scaled trains out of paper and then ramming them into each other will completely destroy both of them?

 

[Thomas B]

How have you determined that the taped connections are a properly scaled down version of the actual truss seats that were used?

I'm going to experiment with different loads and safety factors. Like: they hold with the normal load of 2 batteries. And still hold with 4. (And the whole building holds up if the loads on all the floors are doubled to four.) But an indvidual floor will collapse if loaded with 6 batteries. Something like that. I'm not going precisely model the actual safety factors (I'm not building "to code") I just need for the building (and the individual floors) to not be at the breaking point before the collapse is initiated.

 

[Gamolon]

That's because at their scale they're just way too strong for the forces involved.

How did you determine that?

How will you determine that the scaled tower you build IS properly scaled for the forces involved?

What determines if models have been properly scaled to properly show the the proper forces?

 

[benthamitemetric]

Wait... What? You honestly think that building two scaled trains out of paper and then ramming them into each other will completely destroy both of them?

And not only that, he seems to assume it will tell him something meaningful about how real trains would act in such a collision. Maybe the paper trains will destroy each other in some way and maybe not. In any case, it will have nothing to do with how the real trains will behave in the same way his paper tube model has nothing to do with how the towers behaved, except at such a high level abstraction as to provide no actual insight at all (e.g., if you overload a structure, it will fail in some way").

 

[Thomas B]

Wait... What? You honestly think that building two scaled trains out of paper and then ramming them into each other will completely destroy both of them?

Sorry ... I thought you'd fill in the details. I meant "paper trains" in the sense that my models are "paper buildings". Paper and cardboard structural components. Batteries for inertial loads.

 

[Thomas B]

How did you determine that?

I thought you were familiar with Tyco trains.

 

[Gamolon]

I'm going to experiment with different loads and safety factors. Like: they hold with the normal load of 2 batteries. And still hold with 4. (And the whole building holds up if the loads on all the floors are doubled to four.) But an indvidual floor will collapse if loaded with 6 batteries. Something like that. I'm not going precisely model the actual safety factors (I'm not building "to code") I just need for the building (and the individual floors) to not be at the breaking point before the collapse is initiated.

How will you determine that your model floor loads properly scale with the actual floor loads of the real WTC floors? Are you using numbers or calculations of some kind?

 

[Thomas B]

he seems to assume it will tell him something meaningful about how real trains would act in such a collision.

There is no in principle difference between my work with these models and, say, Mick's use of aluminum cans to illustrate basic properties of buckling. Mine is just a little more elaborate. Mick's cans do tell us "something meaningful" about how columns buckle.

 

[Thomas B]

How will you determine that your model floor loads properly scale with the actual floor loads of the real WTC floors?

They don't really have to. The truther / Hoffman argument is that no structure can be built such the top part destroys the bottom part in a gravity-driven collapse. I've steel-manned it a bit by specifying that the structure has to be relatively homogeneous through its length (equally spaced and loaded floors) and that it has to be able to survive a bit of stress testing. But it's definitely not going to represent "the real WTC". As long as the model collapses, I've demonstrated something. At least to my own satisfaction. From there, yeah, maybe I'll try to model the real WTC more closely. But the prototype just needs to behave roughly right.

 

[benthamitemetric]

There is no in principle difference between my work with these models and, say, Mick's use of aluminum cans to illustrate basic properties of buckling. Mine is just a little more elaborate. Mick's cans do tell us "something meaningful" about how columns buckle.

There is a difference though in that Mick actually thoughtfully considered what he was trying to model, which was simple buckling, and chose a simple model to that end. You, in contrast, are choosing to model something complex that you do not even understand and, along the way, are making simplifying assumptions you do not seem to appreciate. That you can't properly scale for gravity should be a reason to give more thought to your highly complex model; instead, you use it as an excuse to give no thought to the key aspects of your model. You've made a series of arbitrary choices about what construction materials to use and in what proportion (paper and cardboard), what facets of the actual towers to omit (nearly all of them, such as actual connections), what facets of the towers to include (essentially none of them, other than proportional height and width), and the aspects by which you would judge your model against the real collapse.

 

[Gamolon]

They don't really have to. The truther / Hoffman argument is that no structure can be built such the top part destroys the bottom part in a gravity-driven collapse.

Mick did that I thought? Is Mick's model not considered a structure?

 

[Mick West]

There is no in principle difference between my work with these models and, say, Mick's use of aluminum cans to illustrate basic properties of buckling. Mine is just a little more elaborate. Mick's cans do tell us "something meaningful" about how columns buckle.

What's the meaningful thing you are attempting to convey with your models?

A paper tower illustrates some concepts, and could certainly illustrate (if sufficiently large) the contribution of internal bracing with floors to the stability. But it's not really useful to the topic of this thread which is building a model that will collapse top-down, like WTC 1 and 2 did.

A fundamental issue here is that of using a single sheet of material for the entire wall. The world trade center did not collapse to the ground because columns, or walls of columns, failed. It collapsed because the connections between and within building systems failed. i.e. the floors were ripped from the walls and core, leaving them isolated. Then the connections between vertical column sections failed, separating into pieces, which then joined the mass of falling debris.

So to illustrate this, your floors need to separated from the walls and the core (if any) and then the outer wall and inner core need to fall to pieces.

Paper is not going to do this. My model did.

You need to focus on modeling the connections.

 

[Thomas B]

You, in contrast, are choosing to model something complex that you do not even understand...

I'm trying to model something in order to understand it. You're right that I don't understand how the WTC collapsed. I'm not sure in what sense your comment is trying to make a contribution.

 

[Thomas B]

Mick did that I thought? Is Mick's model not considered a structure?

I think that's worthy of a separate thread. Maybe the original thread on the models?

 

[Mick West]

More explicitly, an illustrative model of the collapse would ideally show the disintegration of the outer wall into segments, like this.

 

[Mick West]

I think that's worthy of a separate thread. Maybe the original thread on the models?

How is it not a structure in the context of Hoffman's challenge? (which is the topic of this thread)

 

[benthamitemetric]

I'm trying to model something in order to understand it. You're right that I don't understand how the WTC collapsed. I'm not sure in what sense your comment is trying to make a contribution.

You see, I don't actually believe that. With your past threads, you have established a history on these forums of misrepresenting your experience with and views on these topics and so I believe you are more likely trying to use this thread to demonstrate that you believe Hoffman was correct. The way you dismiss, ignore or nitpick at legitimate criticisms to your approach here, which isn't consistent with a "trying to learn and get it right" mindset, reinforces that. As such, I am just pointing out the flaws in your methodologies along the way so that the ultimate conclusion you are working towards remains in proper context.

 

[Thomas B]

Paper is not going to do this. My model did.

We'll see about the first. So far it's fun trying.

I have long complicated answer to second that I don't think anyone on this thread is actually interested in. I don't think your model demonstrates anything that challenges the truthers' understanding of building structures and collapses. If you want to revisit your model and listen to yet another critique of it (I think you've already had plenty of pushback from truthers trying to tell you why they don't find it persuasive) maybe we could start a thread on that.

 

[Gamolon]

I think that's worthy of a separate thread. Maybe the original thread on the models?

Why a separate thread? You just stated that the truther / Hoffman argument is that no structure can be built such the top part destroys the bottom part in a gravity-driven collapse. Did Mick not create a "structure" whose "upper part" destroyed the "bottom part" in a "gravity-driven collapse"?

 

[Mick West]

We'll see about the first. So far it's fun trying.

A sheet of paper is not going to fall to pieces. To carry a load vertically it needs to be intact. So unless you introduce 3d structure into the walls then nothing will come of it.

We'll see about the first. So far it's fun trying.

I have long complicated answer to second that I don't think anyone on this thread is actually interested in. I don't think your model demonstrates anything that challenges the truthers' understanding of building structures and collapses. If you want to revisit your model and listen to yet another critique of it (I think you've already had plenty of pushback from truthers trying to tell you why they don't find it persuasive) maybe we could start a thread on that.

That's not the question. How does it not meet Hoffman's challenge other than the trivial aspect of aspect ratio? Obviously, it is a structure.

 

[Thomas B]

How is it not a structure in the context of Hoffman's challenge? (which is the topic of this thread)

Did Mick not create a "structure" whose "upper part" destroyed the "bottom part" in a gravity-driven collapse"?

I feel like this is an unnecessary detour, and I'm having more fun building models to illustrate my ideas.

I think I can reproduce Mick's model using my materials? Would that give us some common ground?

 

[Mick West]

I think I can reproduce Mick's model using my materials? Would that give us some common ground?

Go for it. Come back when you have a video of it collapsing.

 

[Gamolon]

I feel like this is an unnecessary detour, and I'm having more fun building models to illustrate my ideas.

I think I can reproduce Mick's model using my materials? Would that give us some common ground?

How is this a detour? It's directly related to the "Hoffman challenge can't be met" title of this thread. Can you just answer the question please? Did Mick not create a "structure" whose "upper part" destroyed the "bottom part" in a gravity-driven collapse"?

 

[Gamolon]

Go for it. Come back when you have a video of it collapsing.

How does one scale wind forces?

 

[Thomas B]

Go for it. Come back when you have a video of it collapsing.

I think I've mentioned this before, but this is one of the things I find puzzling about your exercise. Why did the experiment need to be run? Why the need for video evidence? If you just describe the model, we know how it's going to respond.

Suppose I used my cardboard instead of wood and made the lower columns 12 inches and the upper columns 4 inches. 3 inch floor spans. Clear tape for floor connections strong enough to hold one 9V battery on each floor. But weak enough to collapse when hit by another 9V battery dropped through the height of one floor.

(Yes, I've got all the parts cut and just need to test the connections.)

This will obviously stand up and then collapse just like yours did when I get the connections right. But you would need a video to believe it? I don't understand why.

Obviously all the dimensions and even the materials are arbitrary. You can make the columns shorter or longer and the floor spans as long as the cardboard allows. Everything depends on the floor connections. In fact, in an important sense, the floor connections are the only structurally interesting thing about the model. Make them a little stronger and the collapse is arrested. Make them a little weaker and the thing falls apart under its own weight before you even begin.

So let me ask you. If I do build this thing, and I do film it collapsing, what hypothesis of yours have I tested? Did you think it couldn't be done?

 

[deirdre]

We'll see about the first.

there is nothing to see. a single sheet of paper folded into a tube is not going to miraculously pop apart in sections.

it wouldnt be that hard a process really to build a mini model. Note corners are overly strong so you cant have like a 4 inch model because that is basically all corner.

you can buy different thicknesses of dollhouse wood strips (to taper the columns as you go up). they basically cut with a razor blade so pretty easy to get even lengths. glue them all together with elmer's school glue in the style of the Twins exterior columns....

glue on some tiny floor seats/brackets...

do some experiments (dont use your mesh ... any wood with the brackets glued on will do for experimentation) to see how much weight each bracket and glue will hold before breaking.

 

[deirdre]

If you just describe the model, we know how it's going to respond.

are you just making up arguments to irritate people? how many times have people described to you how the Towers were built and how they collapsed? personally i DO not need a model to understand their description, but apparently you and the OP do... or you wouldnt have started this thread.

 

[deirdre]

made the lower columns 12 inches and the upper columns 4 inches.

they need to be thicker on the bottom and thinner on the top, that's what is meant by tapering. (obviously not these exact dimensions, its just what i had in my dollhouse box)

 

[Thomas B]

It's directly related to the "Hoffman challenge can't be met" title of this thread. Can you just answer the question please? Did Mick not create a "structure" whose "upper part" destroyed the "bottom part" in a gravity-driven collapse"?

I already addressed this in the OP, where I mentioned that one possible answer is, "Mick already met the challenge. Done." If that satisfies you then this thread is of no interest.

What is strange is that those of you who are so certain that Mick's model does meet the challenge, seem pretty sure that my model can't. I.e., that using much lighter structural materials and much heavier (relative) loads will not be able to prove even what Mick already has proven can be done.

I think I can easily replicate Mick's result. And then I can go on to build a model that can prove even more.

 

[Thomas B]

they need to be thicker on the bottom and thinner on the top, that's what is meant by tapering.

They aren't on Mick's model.

 

[Jeffrey Orling]

In post #94... I described a model which could easily be built at home. It mimics the structure of the twin towers...

The perimeter is made of lattice sticks... 1/2" x 1" x 24" long (will do) and lightly tack them one to the other... If you want to get fancy you can cut every other one into 4" sections... use them as spacers... so that when the assembly of one side is completed... it openings at every other column (windows).
Use a toothpick to apply a small dab of glue- Make the side w/ 9 pieces 24" long and with spacers between the assemble will be 18" wide. Make 16 of these side sections

Next drill 1/16" holes at 5" from one end in every 3rd strip... you will insert short pieces of tooth picks into the holes (beam seats)

Next drill holes at 11" from the end... then drill holes at 17" from the end and finally drill holes at 23" from the end.

Now tack 4 facades together pinwheel style to make a 4 sided open tube that is 18 1/2" x 18 1/2" OD and 17 1/2" x 17 1/2" ID

Now you need to cast the floors from plaster. The floors will be 1/4 thick x 17 1/4" x 17 1/4.... allowing 1/8" clearance to the inside of the perimeter walls.

Make a form from 1/4" lattice strips.... so that the inside is 17 1/4" x 17 1/4" Screw them to a sheet of plywood covered with food wrap or waxed paper. Mixed the plaster loosely and pour it into the for to the top edge of the lattice. When dry, unscrew the lattice and carefully lift the cast plaster sheet... this is the floor slab. You'll need to make 4 floors for each section.... total 14.

Next break the toothpicks in half and insert them into the lowest set of holes.
Carefully place one the the cast plaster floors on to the lowest set of toothpicks.... Then insert the next row (from the top) and then carefully lower the next floor in place. repeat until all 4 floors are done for each section.

Next carefully stack one section 18 1/2 x 18 1/2 x 24 on top of one another with a toothpick place a dab of glue on to of the 1/2 x 1" lattice pieces and the place the next section on top and repeat until your model is 8' tall... 4 sections... 16 floors

++++

Set up video cameras
fill a pail with sand and some gravel mix and the from a ladder pour the mix on to the top floor of the top section.
When the load is too much for the plaster the floor will fail... and then all the mix and that floor in parts will fall into the floor below and continue down to the last floor.
it's more than likely that the collapse will also cause the wall to fall away in pieces... if the tack connections fail to maintain the tube's integrity.

++++

Of course this is not a literal scale model... but it has the features of the construction of the twin towers... cast floors, stick perimeter panels... truss supports. It will stand on it's own and it will collapse from a ROOSD load.

Don't waste your time with paper... to model the twin tower collapse.

 

[deirdre]

They aren't on Mick's model.

mick doesnt have 12 inch columns on the bottom and 4 inch columns at the top either. so what's your point?