Gamolon
Active Member
Nope.1:1000 is much easier to build on my desk. So if you're happy with those conditions, I'd be grateful.
We're now testing your understanding of scaling and models.
Both models should act the same.
Nope.1:1000 is much easier to build on my desk. So if you're happy with those conditions, I'd be grateful.
the load didn't provide the bracing, the bracing provided the bracingThis is literally my initial reaction to Mick's conception of the WTC tubes. Somehow they were structures that couldn't stand on their own but could stand when loaded with at least twice their weight (because some of that load also provided lateral bracing). I'm trying to understand it by building such a structure.
That's an interesting possibilty. I'll have to think a little more about that. We agree that their connection to the ground was stronger than those joints, right?If you hit one of the panels in my photo with a wrecking ball, the joints would sever, and it would break off.
So it's fine if I build the smaller one first?Nope.
We're now testing your understanding of scaling and models.
Both models should act the same.
I just meant that the floors provided the load and the bracing.the load didn't provide the bracing, the bracing provided the bracing
Why?So it's fine if I build the smaller one first?
I hadn't thought of that. Thanks. Will get back to you when I make some progress.then re-read what i actually wrote
We can save you the trouble of building anything.So it's fine if I build the smaller one first?
I would use different grades of paper and different amounts of tape. That is, I would scale those factors too. But, yes, my goal is to make a desktop model in paper of the collapse of a 1700' steel-framed building.We can save you the trouble of building anything.
Do you think the 1:1000 scale model will act the same as the 1:100 model both using paper and tape?
How did you determine that the paper for your 1:1000 model is scaled down correctly and models the inherent characteristics of the actual steel façade?I would use different grades of paper and different amounts of tape. That is, I would scale those factors too. But, yes, my goal is to make a desktop model in paper of the collapse of 1700' steel-framed building.
That is exactly what I (and others) have been trying to explain to Thomas B.I believe that you can't use physical scaled models to study the collapse. Strength of materials cannot be scaled. Or... what materials would you use to have the model behave exactly as the full size structure... in some or all aspects/conditions?
What is constant is gravity.... that is not scaled. Some aspects can be studied with a model... but it would be impossible to make a small scale model collapse exactly as the towers did.
What type of paper are you using for your 1:1000 scale model?I would use different grades of paper and different amounts of tape.
I think I keep explaining this. I do it experimentally. The structures I build have to be able to support a significant load under significant lateral forces.How did you determine that the paper for your 1:1000 model is scaled down correctly and models the inherent characteristics of the actual steel façade?
What type of paper are you using for your 1:1000 scale model?
The paper is 30 cm x 41 cm and 90 g/m2.
And you think paper and cardboard replicate the scaled down forces/loads of the actual towers? Without doing any math whatsoever?I think I keep explaining this. I do it experimentally. The structures I build have to be able to support a significant load under significant lateral forces.
You're making assumptions about what I have tried and who I've talked to.I asked asked you this before. Take your paper and tape model ideas to a couple licensed engineers and see if they agree that your model will help you understand the collapses of the towers.
Let us know what they say.
So your paper is about 112 microns thick (.112mm) for the 1:1000 scale model. What paper thickness would you use for the 1:100 model?
So you have talked to engineers and explained your paper and tape model and what you are trying to accomplish?You're making assumptions about what I have tried and who I've talked to.
You also seem unware of how engineers actually teach these principles to their students. The structural behavior of paper is very instructive.
And you are making assumptions also. I worked in an engineering firm for years with all kinds of engineers.You also seem unware of how engineers actually teach these principles to their students. The structural behavior of paper is very instructive.
Please provide evidence to support your claims.You're making assumptions about what I have tried and who I've talked to.
You also seem unware of how engineers actually teach these principles to their students. The structural behavior of paper is very instructive.
Or... what materials would you use to have the model behave exactly as the full size structure... in some or all aspects/conditions?
Young's modulus for steel is about 200; for paper, as far as I can tell, it's about 5. But the steel used in WTC can be measured in inches whereas for paper we're talking about thousandths of inches. So there's some scaling on the order of 1:1000 there somehow.Without doing any math whatsoever?
Withdrawn.Please provide evidence to support your claims.
They said, for example, that if you want to understand the strength of a box column, just fold a piece of paper four ways.What did they say?
That's not what I asked you.They said, for example, that if you want to understand the strength of a box column, just fold a piece of paper four ways.
Please address post #258They said, for example, that if you want to understand the strength of a box column, just fold a piece of paper four ways.
He withdrew his claims in Post #264.Please address post #258
They said, for example, that if you want to understand the strength of a box column, just fold a piece of paper four ways.
The idea, as I understand it, is to show how much stronger a box column is than the steel plates it is made of. For example, a thin steel plate that is long enough (basically a strip of steel) will buckle if you stand it on its end. But if you weld four strips together the resulting column will stand up easily and even be able to support some weight. This can be demonstrated with that folded piece of paper.Were they comparing the strength of a flat piece of paper with the strength of a piece of paper folded up into a box column?
That would indeed be informative, but it doesn't tell you anything about structures made from other materials or at other scales.
For one you should compare the strengths of columns with the same cross sectional area... and of course the same material. Columns need strength in both the X and Y axes. Box and WF sections accomplish this. I believe WF are more economical to make as they can be rolled. Boxes need to be "assembled". I suppose at some size point (cross section) there is limit to manufactured sections.... then engineer would go to built up sections if more strength were required.The idea, as I understand it, is to show how much stronger a box column is than the steel plates it is made of. For example, a thin steel plate that is long enough (basically a strip of steel) will buckle if you stand it on its end. But if you weld four strips together it will stand up easily and even be able to support some weight. This can be demonstrated with that folded piece of paper.
I don't know yet. Until I get any model to collapse progressively, figuring out how (or whether) to scale it one way or another is not my main concern.So your paper is about 112 microns thick (.112mm) for the 1:1000 scale model. What paper thickness would you use for the 1:100 model?
Volume would be 1:1,000,000,000 then.1:1000 is much easier to build on my desk. So if you're happy with those conditions, I'd be grateful.
I thank you for your input. This is the general tenor of the message I'm getting here. Still, some of the pushback is giving me ideas to try. I'm not giving up yet. But you are of course free to ignore me.Hopeless!
I'm not sure how closely you've been following the thread. We're at paper.So... Aluminum is weaker than steel... cardboard is weaker than aluminum.
Understood. Different materials have different properties. A wide flange section of paper is weak than one made from alum or steel. I don't think you can find a material which scaled down behave like the scaled up steel does.I'm not sure how closely you've been following the thread. We're at paper.
He could use steel "plates" for box columns, spandrels etc. that are 1:1,000 the thickness of the original steel. In the upper floors, that would e.g. be 0.000,020 m thin (20 micrometers) insteaf 0.020 m (20 millimeters). This is pretty much within the range of common gauges of houshold aluminium foils.So... scaling down from full size... at what point (how "small") will the model not collapse?
Gravity is not scaleable
Strength of materials is not scaleable. You would have to select materials of less strength... no?
So... Aluminum is weaker than steel... cardboard is weaker than aluminum.
Interesting. At one point I bought a bunch 15 gram lead plates at a hobby store. The plan is in fact to distribute about 20 of them throughout the building as dead weight.If all dimensions are scaled 1:1,000, then mass also is 1:1,000,000,000.
Your model would weigh only 280 grams then,
This level of complexity if of course not realistic. I'm happy to reduce this by roughly 1:1000. So about 4 seats x 6 or 7 floors with 40 or so grams of lead on each.yet have to model the equivalent of 26,400 truss seats.
Don't we just solve this by adjusting the dead loads *on* the structure. Is there a useful difference between being a 1000 times heavier and gravity being a thousand times stronger?But they would have to be a thousand times heavier somehow, or gravity a thousand times stronger...