I need some help debating a truther

[pipelineaudio]

After linking the NIST WTC7 link http://www.nist.gov/public_affairs/factsheet/wtc_qa_082108.cfm i was answered by the following

the link refers to progressive failure due to fires causing main supports to fail.

ok, let's say this is possible, and i'm sure it is. the key term here is progressive. that collapse was not progressive.

in a natural collapse of a building, say due to a fire, different sections will first collapse and then others due to that, and in general at least a part of the building will remain intact.

but truly none of that matters, none of their explanations matter, because the building did not collapse in the way described. the entire building collapsed, all of the supports, from the ground up, all gave, simultneaously, which is not a progressive collapse but an instantaneous one.


these are progressive collapses


http://www.youtube.com/watch?v=h7BHAQkTnyE

http://www.youtube.com/watch?v=tIsE8CkZI6U

this is to show also how it is not even easy to demolish a building on purpose this way.

http://www.youtube.com/watch?v=fiNrz...eature=related

this is what a highrise implosion looks like. minus the explosions much like wtc towers. obviously, if it was going to be done professionally they'd need to take more care of hiding any sorts of explosions. which, if you believe, a building can be destroyed this way by accident, you must also believe that hiding the explosions, or detonating the building in a more discreet way should be possible.

http://www.youtube.com/watch?v=8U4erFzhC-U

this is what a plane crash in a building should look like.


http://www.youtube.com/watch?v=s87e6...eature=related

in this one, you need to go to the end of it, the technique used here is slightly different, the building is more irregularly shaped, but i posted it because it helps you notice that the bottom must go first in order for the higher parts to fall, which no matter how much fire you get in upper floors won't happen.

support beams also must fail at various heights, as you've seen in the fail video, other parts of the building will still be strong, and will impede the fall of a building potentially to the point of halting it completely as in the fail video.

http://www.youtube.com/watch?v=GtIjU...eature=related

i'd also like to point out that progressive collapse is also a term used for demolition. they will progressively collapse buildings, usually wider ones, and usually if they want to get it to fall in a specific direction. if say a building is wide and a high part is on one side, they will first collapse the low side, progressively, so that the high side will fall into the footprint of the lower part. in a uniform building they need to get it to fall straight down into its own footprint, such as a building like 7 and the other wtc buildings. honestly i don't know all the subtleties of demolitions, there are different kinds for different situations, and some are called progressive demolition, which a term that can be used for natural demolition as well, although the key word is progressive. but wc7 had one major fail in it, and then the whole of it harmoniously collapsed.

i'd go through more examples, but you could research it more too.


or just tell me, in your own words, knowing the laws of physics, how a failure this way can occur.

one or more support beams in an isolated area of the building will not cause it to fail uniformly in this manner.

First of all, how does NIST define progressive collapse. I figure any collapse is a progressive collapse, it just progresses quickly

 

[Oystein]

Hello pipelineaudio,

I am not sure I can help a lot, as I am not an expert on these things, and have not looked too deeply into the NIST model.

You are lucky in that your buddy is one of the rare truthers who puts some efforts into research and does not only appeal to imagination and ignorance.

What NIST means by progressive collapse is different from what demolition pros mean when they demolish a larger buildinh progressively. In the latter case, they just time their explosives accordingly in progressive sequence. For this to work it is actually necessary that the building does NOT collapse progressively on its own too fast after the first blast, as that would get in the way of the controlled demo of the rest.

What NIST refers to is this: Structural elements buckle, break and collapse locally when they exceed their load-bearing capacity. This failure will lead to load distribution - the load formerly carried by the failed elements will be shifted to adjacent elements, whose load is thus increased. Progressive failure occurs if and when these adjacent element also exceed their capacities after the redistruibution.

Question is no: How fast does this occur?
The examples your friend refers to in his first 2 yt links are instructive and well chosen, however they can't be applied directly to WTC7.
For startes, both seem to be more conventional designs where vertical loads are carried by columns that are spread out more evenly about the area. WTC is different from that in that most of the vertical loads are carried by core columns which cover only a fraction of the footprint.
Secondly, the computer model is played in slkow motion, and the Utrecht-building is a lot smaller than building 7.

Now I start speculation: I would think that progressive collapse is something that accelerates, as less and less columns get burdened with higher and higher additional loads. This would mean that the first steps of progression occur slowly, seconds apart maybe, but zhat towards the end, the remaining elements fail in very rapid succession. This will happen especially when the point is reached where ALL of the remaining columns together can't bear the remainder of the loads. In that case, near-instantaneous failure should not be so surprising.

 

[pipelineaudio]

Thanks a million!

 

[Sabretooth]

I think Alienentity has a good video for you to watch:
http://www.youtube.com/watch?v=G8yfNLSp_Pw