Tower Collapse Questions for Critical Thinkers

No, it DOESN'T MATTER if I drop it, or break it apart into tiny weights. The weight will still eventually be ON my porch, even if not all at once. I believe its called "static load", but I could be wrong. Like I said, I am not an engineer.

It doesn't matter. Either way, my porch WILL collapse.
 
kylebisme said:
You are correct, but you are missing Bill's point. You could take a giant 2,000 pound weight that covered the area of your porch and collapse it by dropping that weight from high enough. However, if your broke that weight into a bunch of pieces, they wouldn't hit at the same time, and hence would have to be dropped from far higher to collapse your porch.
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To the degree you are correct, depending of the weight and the porch, the momentum can be sufficient to collapse your porch, anyway.

It was on 9/11.
 
kylebisme said:
You are correct, but you are missing Bill's point. You could take a giant 2,000 pound weight that covered the area of your porch and collapse it by dropping that weight from high enough. However, if your broke that weight into a bunch of pieces, they wouldn't hit at the same time, and hence would have to be dropped from far higher to collapse your porch.
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Why exactly wouldn't they hit at the same time?If they're dropped from the same height and accelerate due to gravity everything should fall in the same amount of time regardless of whether it's a solid block or the same sized aggregate of particles.
 
kylebisme said:
All good, and I thank you for the apology. I also respect your difficulty with technical jargon as I know many are not comfortable with such things. This is why I've been attempting to speak in common terms, not out of any trouble with the technical descriptions myself.
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Trust me, you're not impressing anyone here with your technical knowledge. Quite the opposite actually.
 
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HeyLeroy said:
The lower section would not be exerting a force greater than the falling portion; the falling portion has momentum.
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momentum = mass x velocity.

force = mass x acceleration

The two are related, but not the same; mass doesn't doesn't gain force though momentum. (That really isn't quite true, but the increase is immeasurably small until coming very close to the speed of light, which isn't rightly relevant here.)

HeyLeroy said:
The only reason the lower portion held the upper portion (I refrain from using your term, "block...
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Not that I was not commenting on the towers there, but rather the conversation you responded to was about these these collapses.
 
I just spoke to the engineer who designed my overly simple porch, (my father) and I spoke to the builder (myself and my BIL, who is also a structurl engineer) and they have all agreed that it wouldn't matter if the weight was in pebbles, or toasters, it would still cause the catastrophic failure of my porch.
 
kylebisme said:
momentum = mass x velocity.

force = mass x acceleration

The two are related, but not the same; mass doesn't doesn't gain force though momentum. (That really isn't quite true, but the increase is immeasurably small until coming very close to the speed of light, which isn't rightly relevant here.)


Not that I was not commenting on the towers there, but rather the conversation you responded to was about these these collapses.
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What the Hell?

Mass and force are related only through acceleration.
a 1 kilogram mass(9.8 N at 1 g) can exert a force of 9800000 N quite easily.
take it up to 1000 m/second velocity, and stop it in 10 milliseconds
 
triforcharity said:
Have you JUST called EVERY SINGLE PERSON on this forum a COMPLETE IDIOT???
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I did nothing of the sort. I believe we are all intelligent, but I know we all have different interests and many never found much use for studying physics. My comment was not even directed at forum members, but rather a comment on people in general.
triforcharity said:
No, it DOESN'T MATTER if I drop it, or break it apart into tiny weights. The weight will still eventually be ON my porch, even if not all at once. I believe its called "static load", but I could be wrong. Like I said, I am not an engineer.

It doesn't matter. Either way, my porch WILL collapse.
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It does matter, for the reasons I explained above. Also, static load is the weight of the porch itself, dynamic load is what it is designed to hold beyond it's own weight.
Reactor drone said:
Why exactly wouldn't they hit at the same time?
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Because we broke them apart. Even if you could just neatly stack them all together tightly hovering in mid air to drop them from there, air resistance would cause them to push each other apart. Also, the pieces impacting on each other would absorb some of the force rather than transferring it to the deck below, acting like crude shock absorbers.
 
triforcharity said:
I just spoke to the engineer who designed my overly simple porch, (my father) and I spoke to the builder (myself and my BIL, who is also a structurl engineer) and they have all agreed that it wouldn't matter if the weight was in pebbles, or toasters, it would still cause the catastrophic failure of my porch.
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Ask them to read what I wrote instead of presenting your interpration, as I get the strong impression you didn't compherend what said.
rwguinn said:
What the Hell?

Mass and force are related only through acceleration.
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What the hell? I never claimed otherwise, and rather stated exactly that in other terms.
 
Seriously, twoofer, stop pretending that you know what you are talking about. You obviously have no idea.
 
kylebisme said:
Ask them to read what I wrote instead of presenting your interpration, as I get the strong impression you didn't compherend what said.
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I sent it to my dad in his office. I copied exactly what I said, and what you said.

He laughed.

So did my BIL. Actually, he said a few choice words about your intelligence, then laughed.

So, are they BOTH wrong?? I highly doubt that.
 
kylebisme said:
Because we broke them apart. Even if you could just neatly stack them all together tightly hovering in mid air to drop them from there, air resistance would cause them to push each other apart. Also, the pieces impacting on each other would absorb some of the force rather than transferring it to the deck below, acting like crude shock absorbers.
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Loads don't just vanish instantly the moment after they are applied. This is easily modeled by the characteristic equation of vibration. This translates to something similar to a sinusoidal wave with an intial magnitude equal to the dynamic load effect of the force and decays down with each cycle.

The period of this sinusoidal wave in the WTC is measured in seconds.
The percent damping, or reduction in amplitude for every cycle is about 10% (which is exceptionally high for a building). This crude shock absorber you're talking about is insignificant.

The tower was doomed once the upper block began falling. Not only because of the forces from the debris impacts, but because the force in the lower block columns from the upper block hadn't unloaded before the upper block struck.
 
kylebisme said:
It does matter [static and dynamic loads] , for the reasons I explained above. Also, static load is the weight of the porch itself, dynamic load is what it is designed to hold beyond it's own weight.

Because we broke them apart. Even if you could just neatly stack them all together tightly hovering in mid air to drop them from there, air resistance would cause them to push each other apart. Also, the pieces impacting on each other would absorb some of the force rather than transferring it to the deck below, acting like crude shock absorbers.
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You post an empty hypothetical. Details matter.

On 9/11, the load was sufficient to collapse the tower.

I'm really not interested in the countless other buildings in the world, if only because no other buildings were constructed like WTC1 and 2 were in ways that are relevant to the way they collapsed.

You, Herrit, Jones, Gage et all are ignorant of that fact.
 
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kylebisme said:
It does matter, for the reasons I explained above. Also, static load is the weight of the porch itself, dynamic load is what it is designed to hold beyond it's own weight.
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Please quote the relevant passage from the IRC (or any building code) which talks about designing porches for a dynamic load.

Heh, I know you can't. It doesn't exist. The only dynamic loads any architecture structure is designed for is earthquakes. For a porch in a region of low snow-fall and non-hurricane region, the porch wouldn't need any capacity greater than a 20psf roof live load and 30psf wind uplift force.

Be careful with what you talk about on these forums. You can't just make up whatever you want. People here earn a living actually doing the things you can only lie about.
 
Newtons Bit said:
Please quote the relevant passage from the IRC (or any building code) which talks about designing porches for a dynamic load.

Heh, I know you can't. It doesn't exist. The only dynamic loads any architecture structure is designed for is earthquakes. For a porch in a region of low snow-fall and non-hurricane region, the porch wouldn't need any capacity greater than a 20psf roof live load and 30psf wind uplift force.

Be careful with what you talk about on these forums. You can't just make up whatever you want. People here earn a living actually doing the things you can only lie about.
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Newtons,

You must be psychic. I live in a NO snow-fall, high hurricane region (Florida) and I just looked at my drawings for my porch. Guess what?

My capacity is 25psf, and a 40 psf uplift. I wanted it stronger, as we do live where many hurricanes can occur in just 6 weeks (2004) I am somewhat anal like that.
 
triforcharity said:
Newtons,

You must be psychic. I live in a NO snow-fall, high hurricane region (Florida) and I just looked at my drawings for my porch. Guess what?

My capacity is 25psf, and a 40 psf uplift. I wanted it stronger, as we do live where many hurricanes can occur in just 6 weeks (2004) I am somewhat anal like that.
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I'm not psychic, I just do this stuff for a loving. With things much much larger than porches. :D
 
I can't believe that this "kylebisme" has managed to generate ten pages of responses to his completely ignorant, and uninformed theories. I guess it's ironic, that a little bit of stupid, can attract the attention of a whole lot of smart. When does it finally become a futile waste of time and words?

L.
 
kylebisme said:
Ask them to read what I wrote instead of presenting your interpration, as I get the strong impression you didn't compherend what said.
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We did read, and it is pure pseudo-scientific gibberish
kylebisme said:
What the hell? I never claimed otherwise, and rather stated exactly that in other terms.
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Yes. Yes you did claim mass=force...
...mass doesn't doesn't gain force though momentum...
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Although to be painstakingly fair, bending over backwards, as it were, it is through change in momentum over time that "mass gains force", so from a purely pedantic POV, you are correct...
 
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