Moderated Steel structures cannot globally collapse due to gravity alone

C7

Not rhetorical. Do you even know what rhetorical means?

How much was shedded in the first split seconds of the collapse? Rough estimate. What weight would have hit the floor below?
 
funk de fino said:
C7
How much was shedded in the first split seconds of the collapse? Rough estimate. What weight would have hit the floor below?
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3bp said:
at some point (2, maybe 3 seconds) after initiation the exact amount of material ejected becomes irrelevant to your arguement.
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Point taken. Bazant claims that the ejected material is not a factor after the first few seconds.
 
If I stood beside the base of WTC1 and threw a stone as hard as I could the stone would travel (say) 100 yards. If I then threw the same stone exactly the same way from the roof of WTC1 how close would it land to where the first stone landed ?
 
Dave Rogers said:
You are attempting to prove that steel structures cannot collapse due to gravity alone,
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No, I just saying that Bazant's calculations are based on a lot of assumptions and conditions that do not conform to the actual event.

which is itself an absurd contention
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Ya got that part right.

Even if you were to demonstrate that Bazant's model were invalid, you would at best have demonstrated that one specific structure would not be expected to collapse globally in one specific scenario.
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NIST did not explain the total collapse of the Trade Towers.

Bazant's theory has been put forward as an explanation of the collapses. It is not.
 
Christopher7 said:
Good point. How does a force pushing downward eject something sideways at 54 mph?
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From what I've read some people speculate that the box-column perimeter asemblies flexed, storing enough poetential energy to cause them to spring out from the building. But if you try to flex a box-column it will just kink or buckle before it flexes as far as I know.
 
Am I gonna have to bring out the fist falling on a Big Mac analogy again?

Oh wait, I just did.

TAM;)
 
bill smith said:
From what I've read some people speculate that the box-column perimeter asemblies flexed, storing enough poetential energy to cause them to spring out from the building. But if you try to flex a box-column it will just kink or buckle before it flexes as far as I know.
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That's correct. Structural steel will bend a little and "spring" back but it will stay bent past a certain point and is not capable of storing a great deal of "spring" energy.

At most, gravity can cause the exterior walls to be pushed out of the way by falling debris but falling debris cannot rip these interlocking sections apart and hurl them 400-500 feet in all directions at speeds of 50mph or greater.
 
Christopher7 said:
That's correct. Structural steel will bend a little and "spring" back but it will stay bent past a certain point and is not capable of storing a great deal of "spring" energy.

At most, gravity can cause the exterior walls to be pushed out of the way by falling debris but falling debris cannot rip these interlocking sections apart and hurl them 400-500 feet in all directions at speeds of 50mph or greater.
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Heiwa pointed out that for columns to travel horizontally away from the building they need to be severed top and bottom. A top-down collapse should always leave the bottom connection intact until the collapse wave reaches it. I think that should mean that the exterior columns should have been peeled away from the building by the collapse wave. As it was a lage fraction of the beams were seen spinning away straight and unbuckled through he air
 
bill smith said:
Heiwa pointed out that for columns to travel horizontally away from the building they need to be severed top and bottom. A top-down collapse should always leave the bottom connection intact until the collapse wave reaches it. I think that should mean that the exterior columns should have been peeled away from the building by the collapse wave. As it was a lage fraction of the beams were seen spinning away straight and unbuckled through he air
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Columns don't need to travel horizontally away from the building to fall clear of the footprint, they only need to acquire a sufficiently large horizontal velocity component. I think you're over-idealising the collapse wave by drawing a clear distinction between the time it arrives at the top and at the bottom of a column section; if you visualise a more chaotic collapse it isn't hard to see how beams could experience a lateral force. For example, if a column tree is disconnected at its top end, and debris is being funnelled to its inside, it will tend to rotate outwards, breaking the lower connection; that rotation will give its centre of mass a lateral velocity component. The result of such a process would be an unbuckled beam spinning away sideways. It's not much different to the toppling that Christopher7 seems to think was inevitable for the top section, except that it can be enhanced by oblique impacts of debris on the column tree when it's in mid-topple - something that couldn't happen with the top section because there was nothing falling on it from above.

Dave
 
Dave Rogers said:
Columns don't need to travel horizontally away from the building to fall clear of the footprint, they only need to acquire a sufficiently large horizontal velocity component. I think you're over-idealising the collapse wave by drawing a clear distinction between the time it arrives at the top and at the bottom of a column section; if you visualise a more chaotic collapse it isn't hard to see how beams could experience a lateral force. For example, if a column tree is disconnected at its top end, and debris is being funnelled to its inside, it will tend to rotate outwards, breaking the lower connection; that rotation will give its centre of mass a lateral velocity component. The result of such a process would be an unbuckled beam spinning away sideways. It's not much different to the toppling that Christopher7 seems to think was inevitable for the top section, except that it can be enhanced by oblique impacts of debris on the column tree when it's in mid-topple - something that couldn't happen with the top section because there was nothing falling on it from above.

Dave
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The collapse may have been chaotic inside the bildinng but the visible collapse wave on the outside was as orderly and neat as you please. The downward forces appeared to be fairly evenly applied to the perimeter walls . Given that the uper connections were boken first and as you say the funnelling rubble inside would have applied a lateral outward pushing force on the still bottom-connected beams surely the tendency would be to peel the outer skin off the building ?. At the very least the snapping of the bottom connections would have taken almost all the power out of the ejection. As it was some of the ejected beams have been measured as travelling at about 70 mph.
 
The way some people are talking, the evidence is SO compelling that Steel structures cannot globally collapse due to gravity alone, and therefore the WTC collapses were impossible they way they were described by NIST and others, I'm surprised it's not some kind of heated global scientific debate by now.

The fact it isn't is telling to me.
 
Gravy said:
http://video.google.com/videoplay?docid=2083421624495848233#5m24s
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It would take a frame by frame analysis to determine if the large section that landed in front of Winter Garden was hinging or falling.

The individual sections sticking in WFC 3 cannot be explained by the 'hinge' factor. They were ripped away from the surrounding sections and hurled over 400 feet where they still had enough lateral force/energy to embed themselves 200-240 feet above the ground.
 
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Christopher7 said:
It would take a frame by frame analysis to determine if the large section that landed in front of Winter Garden was hinging or falling.

The individual sections sticking in WFC 3 cannot be explained by the 'hinge' factor.
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Maybe I'll ask you: if it is indeed impossible for the buildings to have collapsed the way the "official" narrative describes, why is this debate only happening on obscure internet forums and not in the global scientific community?
 
Christopher7 said:
That's correct. Structural steel will bend a little and "spring" back but it will stay bent past a certain point and is not capable of storing a great deal of "spring" energy.
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Yes this is correct. I'll elaborate if I may, because I get that little spark when someone understands. I don't mean to be condescending but others might like to have more info.

Look at the following stress/strain (Force/Area v [elongation-original length]/ original length) graph for a typical metal.

http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Mechanical/Tensile.htm

Ever remember doing Hooke's Law at school by hanging various weights off of a spring and measuring the extension of the spring v load? Well the linear part is the same thing, it's elastic. The metal will "spring" back to it's original dimensions once the load is released as long as the stress the stress remains on the straight line. Again, as C7 states, once the load reaches a certain point, called the yield point, then the metal will no longer spring back to it's original shape, but is plastically deformed; or for want of a better phrase: bent.

Now imagine as you increase the stress from zero; follow the curve up, past the yield point, then stop at any stress before the UTS (see link) and then imagine reducing the stress gradually to nothing. The downward curve will not follow the one one the way up, but will now drop at the same rate as the original linear (elastic) part landing somewhere to the right of zero on strain axis. That's difference is how much the metal has been elongated or strained.

The two straight lines are parallel, but the one further to the right has a higher yield point. The next time you start to apply a load the graph will follow the second linear part. That is you have increased the yield point of the metal by previously bending it, but you have also made it more brittle (reducing the elongation after the yield point). Therefore the part of the graph between the yield point and the UTS is the part where "work hardening" occurs.

If we take a brittle material like glass or a ceramics then the linear portion of the graph extends right up until the material breaks. There is little to no plastic deformation (yielding) and therefore no work hardening.

Christopher7 said:
At most, gravity can cause the exterior walls to be pushed out of the way by falling debris but falling debris cannot rip these interlocking sections apart and hurl them 400-500 feet in all directions at speeds of 50mph or greater.
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I think that one of the things that we just cannot visualise is the tremendous energy stored within the buildings (potential energy). These buildings were so massive and so high that when we think of 12 ton (tonne?) sections being propelled distances we tend to think in more every day terms. When was the last time anyone saw a truck fall from 1/4 mile? The scale is mind boggling, there is a huge amount of energy released. Each time I see a collapse I'm reminded of slow-mo videos of water drops impacting puddles. The original drop is small and only has gravity acting on it's mass yet it manages to propel droplets in all directions, some a significant size and proportion away from the radius of the size of the impacting droplet.

I don't know if this is a good analogy (probably not) but it does remind me how a purely downward force causes lateral motion.
 
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Sunstealer said:
Each time I see a collapse I'm reminded of slow-mo videos of water drops impacting puddles. The original drop is small and only has gravity acting on it's mass yet it manages to propel droplets in all directions, some a significant size and proportion away from the radius of the size of the impacting droplet.

I don't know if this is a good analogy (probably not) but it does remind me how a purely downward force causes lateral motion.
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It is not a good analogy. It's a falling object hitting a flat surface and the energy being deflected sideways.

Bazant says the falling top section came in contact with something that gave way and the accumulated kinetic energy continued straight down.
 
I'd like to play pool against Christopher7, for a large amount of money. It should be easy, because according to his understanding of physics bank shots are impossible, as well as anything except a perfectly aligned cue-ball-hole shot.

But they do provide a good example for how a force is translated from one direction to another.

So, Christopher7, care to expalin how a force pushing in one direction (a cue ball moving) can send a ball it impacts off to one side? If you can understand this simplified case, then we can look at how more complex factors can add even more horizontal velocity.

And, to head you off at the pass, so to speak, I understand you're about to say "but gravity's a constant acceleration, a cue ball is just constant velocity!". Fine. Do the same thing, then, but drop a cue ball onto other pool balls suspended in air. Find out how many of them fall stright down. Report back here.
 
bill smith said:
The collapse may have been chaotic inside the bildinng but the visible collapse wave on the outside was as orderly and neat as you please.
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That's very difficult to say for certain from the videos available. Some don't have the resolution to be entirely certain which parts of the structure have and which haven't collapsed; there's at least one I know of WTC1 that appears, in the early stages, to show the building simply shortening in places, with no clear visibility of the collapse front at all. Later on, of course, when the entire collapse becomes obscured by dust, there's no way to determine any details of the collapse wave at all. And, of course, if columns are being forced outwards by oblique impacts from within, it's the unseen inner collapse that makes the difference.

bill smith said:
At the very least the snapping of the bottom connections would have taken almost all the power out of the ejection. As it was some of the ejected beams have been measured as travelling at about 70 mph.
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I don't know where you get "almost all" from. Remember that the connections between perimeter column trees were bolted. How far can one of the bolts rotate before it snaps? You'd have to ask a structural engineer, but I'd be surprised if they could be bent through anywhere near a right angle before snapping. If the bolts snap while the column is still rotating, they'll have very little effect on the horizontal velocity component; the forces on the base of the column tree are compressive and torsional, so the bolts never act in tension.

What's your source for the 70mph ejection speed, and is that the lateral component or the magnitude of the velocity?

Dave
 
C7,

Ever hit a nail with a hammer & had it fly off sideways?

BTW, if a 4 ton beam asembly is thrown to the side with enough horizontal velocity to make it 400 - 500 feet, then, BY DEFINITION, it has enough energy to embed itself into whatever it might contact at that point.

Short of firing the retro rockets, of course.

tk
 
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