Acceleration of the falling top blocks.

Also the top block did not fall straight down, but it leaned over and started to break apart.

I find it silly to think that say floor 77 remained perfectly intact until floor fell onto it. And then onto floor 76, etc.

And loads being exerted on a vertical 30 ft column would almost instantly be transferred to the structure below, perhaps poping bolts and breaking welds ahead of the falling mass.
 
notheist said:
If you look at the videos you see the side walls peeling away like a banana. And this would cause several floors at a time to become unsupported. In WTC 1 a good portion of the core remained intact with the side walls fallen around it, with 12 people alive inside as well. You can see the core is the last parts to fall.

Each floor does not need to wait to start a downward fall. An avalanche is a good analogy. An avalanche of steel concrete and building contents.
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I have always envisaged the WTC1 & 2 collapses as 'wedge' driven. Akin to splitting a fire log with an axe. I also believe it possible that the building structure actually enabled its own collapse and guided the collapse as if on rails. Thats just me. Probably totally wrong.
 
This all moot given a controlled demolition would not do what you saw on 9/11.

Controlled demolitions ARE gravity driven after all. Controlled demolitions do NOT blow up buildings, but only use explosives to unsupport enough of the building to allow gravity to distroy the structure. On 9/11 it was fire that did the unsupporting.
 
notheist said:
This all moot given a controlled demolition would not do what you saw on 9/11.

Controlled demolitions ARE gravity driven after all. Controlled demolitions do NOT blow up buildings, but only use explosives to unsupport enough of the building to allow gravity to distroy the structure. On 9/11 it was fire that did the unsupporting.
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I know:rolleyes:
 
WTC Dust said:
...Add up all these fractions of a second, and you get something very different from what was seen on 9/11. We saw the buildings
go away in about a dozen seconds. There wasn't enough time
for a floor-by-floor gravity accelerated collapse. The buildings
fell too fast for this to be a proper explanation.
Click to expand...
Show your work.
 
Jackanory said:
I have always envisaged the WTC1 & 2 collapses as 'wedge' driven. Akin to splitting a fire log with an axe. I also believe it possible that the building structure actually enabled its own collapse and guided the collapse as if on rails. Thats just me. Probably totally wrong.
Click to expand...

In many photos after you can see the side wall were pushed outward and into other buildings so yes the top block mass could act like a wedge splitting from the inside and down.
 
Jackanory said:
I have always envisaged the WTC1 & 2 collapses as 'wedge' driven. Akin to splitting a fire log with an axe. I also believe it possible that the building structure actually enabled its own collapse and guided the collapse as if on rails. Thats just me. Probably totally wrong.
Click to expand...
Not totally wrong.

Take care not to push the "wedge" analogy too far. The office space floor separation proceeded many floors ahead of perimeter peel off and fall over. The separation therefore achieved by the mass of material falling in the office space and NOT by wedge action pushing outwards breaking the floor joist connections.

Yes this process had the effect you describe of "guided the collapse as if on rails." The "guiding rails" of the outer perimeter columns remained standing after the falling mass had passed.

And remember that the core failure was happening in about the same time as floor failure - the main mechanism probably strip down of the horizontal beams which were sheared off from the columns. The beam to column connections almost certainly the weakest point in the core.
 
WTC Dust said:
Acceleration is a very good topic. Acceleration takes time. We saw the buildings
go away in about a dozen seconds. There wasn't enough time
for a floor-by-floor gravity accelerated collapse. The buildings
fell too fast for this to be a proper explanation.
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Really? So where did it go? Given you can not make mass just disappear.

And what do you base your observation on? This was the first time anyone saw a building this size collapse. You can not judge it by smaller structures given the fact the scalling issue. Very massive structures will behave differently.
 
WTC Dust said:
I'd like to know which part of what I'm saying you think is wrong.
And, yes, I was a 9/11 Truther before it was cool to be a 9/11 Truther,
because I smelled the burning building, and knew something was wrong
with the explanation.

It's made for an interesting, if insult-filled, ten years.

But enough about me. Talk about the acceleration.
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What of the core that remained standing after the perimiter fell?
 
WTC Dust said:
You're model doesn't account for the fact that the bottom floors can't move until the top floors reach them to deliver the impact.
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Nice to know you are still alive and well, but a bummer that you still haven't figured this out.

You do not have to wait for one floor to hit the next if the perimeter columns are unzipping, as we can see that they do in most of the close-up video. You also ignore the fact that falling fluid will continue to exert a downward force at least equal to gravity in all directions except straight up, and that compressed air can actually add more energy to the reaction because it allows a loosely-packed mass to continue accelerating downward without totally stopping with each impact, even if at slightly less than g. Thus, the need to overcome resistance in the structure below would slow collapse, but not arrest it.

The whole process took closer to twenty than to ten seconds in both towers. There is no need for a magic space-case discombobulator gun or demolition charges.
 
NoahFence said:
What of the core that remained standing after the perimiter fell?
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In some of the videos you can clearly see parts of the core standing after the other wall and floors have fallen away. Hard to see with the dust and all, must be a video of good quality. They only stand for a second or two.
 
notheist said:
In many photos after you can see the side wall were pushed outward and into other buildings so yes the top block mass could act like a wedge splitting from the inside and down.
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A wedge is a better anology than an axe. Especially if the wedge is powered by a hydraulic ram, like an industrial log splitter.
 
leftysergeant said:
A wedge is a better anology than an axe. Especially if the wedge is powered by a hydraulic ram, like an industrial log splitter.
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Yeah......wedge or v through the centre/off centre etc. Top 10 stories being the wedge as it did tilt into such.....sort of. Guided by the central columns on its way down.......possibly. Ripping the structure from inside out. That's my mental picture. Perhaps not as swift as an axe and yeah.......more like the constance of a ram.
 
notheist said:
In some of the videos you can clearly see parts of the core standing after the other wall and floors have fallen away. Hard to see with the dust and all, must be a video of good quality. They only stand for a second or two.
Click to expand...

If memory serves, I think the free standing core was close to 60 stories in the North tower and 40 in the South. There's only a few good videos where the cores can be made out through the dust cloud.

Don't quote me on that though.

eta: of course there's a thread going - http://www.internationalskeptics.com/forums/showthread.php?t=233835

The chopper video is the best one to see the North tower core.
 
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DaveThomasNMSR said:
Wrong, wrong, wrong. The upper sections gather mass, and fall faster and faster. The bottom sections are at rest until they are impacted and incorporated into the falling upper mass, taking on its speed.
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This is shockingly stupid. You should be ashamed of what you're writing here.

Not even going to get into the complete silliness of the "avalanche" metaphor.
 
ergo said:
This is shockingly stupid. You should be ashamed of what you're writing here.

Not even going to get into the complete silliness of the "avalanche" metaphor.
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Explain, What did he get wrong? You can use the big words, we can take it.

;)
 
ozeco41 said:
And remember that the core failure was happening in about the same time as floor failure - the main mechanism probably strip down of the horizontal beams which were sheared off from the columns. The beam to column connections almost certainly the weakest point in the core.
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I am going to have to take issue with that to some extent. I think Bazant may have been a bit off on his calculations that crush-down would precede crush-up. Both could clearly have been going on simultaneously, but the structural elements were all lighter toward the top, and would probably have split apart under their own weight. This would, however, eventually over-load the core columns so that the top ends were begining to separate under the weight of the upper-level debris.

Looking at pictures of some of the perimeter columns I have noticed that not all of the mounting brackets appear to have been pushed very far downward. Some appear almost entirely undamaged. Had the floor slabs been disconnected from the core first, I would expect the brackets on the perimeter to be almost uniformly pulled downward.

The less-damaged brackets suggest to me that there was considerable latteral force applied to help sever the connections.
Bear in mind that the perimeter columns were tie together by threes, that they extended across three floors, and that they were staggered in such a way that outward forces could easily have been transferred several floors downward. Given the advantage of levering, it would not take any great deal of force to move a panel of columns outward by an inch or two, which would seriously weaken, if not break the connection even before weight was applied to a specific floor by the falling rubble.

This also allows the sides of the building to fall away in multi-floor pieces, thus enabling it to simply lean across WTC 5 and WTC 6 to hit WTC 7, the telephone building and the Winter Garden.
 
ergo said:
This is shockingly stupid. You should be ashamed of what you're writing here.

Not even going to get into the complete silliness of the "avalanche" metaphor.
Click to expand...

I will bet ten dollars that ergo will never explain what his objection is in a logical manner.
 
ergo said:
This is shockingly stupid. You should be ashamed of what you're writing here.

Not even going to get into the complete silliness of the "avalanche" metaphor.
Click to expand...

Thanks for this, ergo. I'm filing this in my "Shockingly Stupid and Silly Statements" file, along with this gem:

I'm not sure even a moon-sized field or mountain of rubble, dropped from a height of 12 feet would entirely crush the WTC. No.
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Thanks for playing! :D
 
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