Executive summary: Fires weakened structural members which collapsed, resulting in catastrophe.
There was a link on CNN earlier today about the report and one of the conspiracy folks said (paraphrase) “It’s a load of rubbish, the government is covering it up”.
So, for anyone who was on the fence, or thought that WTC7 came down due to some cause other than the obvious damage, does this report change your mind?
Nothing has changed from what was decided. There were thoughts that the floor joist bolts snapped but upon further review the bolts survived and the sagging joists pulled the walls in to the point where they snapped. This was discovered after they found the joist ends still bolted to the walls.
Since only loonies believed that WTC 7 was “pulled”, I don’t imagine that anybody’s mind will be changed by any of it. The cranks will continue to believe what they want to and the rest of us had the truth confirmed once again.
I’d rather see them explain where the structural member failed and how the chain reaction of collapse spread across the building’s width in an instant. Also how the roof can hit the ground only a second slower than would a bowling ball falling through nothing but air. Buildings can collapse. But they’re not super-critical. Some parts break. Some parts resist. (See the Oklahoma City building.) But even if it all falls down, the parts that go first drag the others after them.
Please see these videos before posting in this thread. Just to be on the same page. Video 1 Video 2 Video 3
Notice how the roof, especially in video 1, is a just slightly kinked but essentially flat +/- 3 feet across its entire 100+ yard span.
You’re talking about WTC1 and WTC2, the Twin Towers. This thread is about WTC7, which collapsed later that afternoon.
I think most people can imagine that pretty well without need for an explanation. One member fails, and it immediately puts a huge amount of strain on its neighbor, which immediately fails, etc.
Why would a bowling ball be expected to fall faster than steel and granite?
I have no idea what you’re saying here.
You can see +/- 3 feet in a small video taken from miles away? One pixel in that video is more than three feet!
Define ‘immediately.’ It’s not, for example, “one nanosecond.” In one nanosecond light only travels one foot. Could it be 0.01s? That’s too fast for “immediately” also, because if a beam were to collapse and the ceiling sag, it’d only fall by about half a millimeter in 0.01s (distance=1/2gt^2). Yet you have to remember that “immediately” has to happen again and again, probably at least a hundred times. Even with a hard-to-imagine 0.01s delay per domino, you’d need about 0.5-1s for the chain-reaction to travel across the large building. Yet even a 0.5s spread between some part of the roof and any other is way more than is observed. 0.5s is actually a decent spread, if you watch any sort of racing. Given the speed the roof finally attains, it would equal several dozen yards. Yet the roof is flat to within a yard or two (and yes, that’s about one pixel of video 1). I’ve been taking the most optimistic estimates, and the result is still off by an order of magnitude.
Anyway, my point is that if you do any sort of math, you’ll realize the roof can’t, just can’t, be perfectly flat. And perfectly flat is what it is.
It did resist as it fell, considering that the building did fall slower than a bowling ball would have. Also, I’m curious about who measured the whole “bowling ball” thing. At what point would you have released the bowling ball to compare the time it fell to the time the building took to fall? It started falling several moments before it picked up critical momentum.
Air pressure inside the building might have been lower due to the fire consuming oxygen inside. This probably made the building “fall” faster than it otherwise would have.
Also, the fires were near the top of the building. If they were much lower, I would have expected the buildings to “topple” instead of collapse.
Too slow to edit, but an example came to mind. If you build a 20 story house of cards, and drop a bowling ball onto it, what happens to the ball? Do the cards significantly alter the bowling ball’s trajectory as it falls? I think you’re significantly underestimating the amount of force and weight being applied here. There comes a point where even the solid structure of a skyscraper can’t resist the weight crushing it from above. The supports for a skyscraper aren’t necessarily perfectly 90 degrees perpindicular to the ground, either, so they’re crushed inward, adding even more weight to the falling section and becoming even more irresistible to the floor supports below it.
Why run the unbelievable risk of planting demo charges? What would it possibly accomplish? Everyone saw the planes hit the other buildings, what could possibly have been so important about making sure WTC 7 collapsed?
The only reason anyone believes this bullshit is because the only buildings they’ve ever seen collapse have been demo’ed. So they watched 7 fall and went, “Duh, um, ahh, building fall down, go boom, just like on TV show!” I’ve wasted too much breath trying to explain to these ignorant trogledites that that is the only way a building can collapse.
I no longer mince words. If you still believe any of that you are a fucking idiot akin to someone believing the Moon landings were faked because the Earth is really flat.
I think you’re signficantly underestimating the strength of a building, which is engineered to be many times stronger than the weight applied to it. Needless to say the building can still fall, but not as if it were supercritical. A house of cards (or those things made of unglued wood sticks) is supercritical, barely strong enough to hold itself.
Um… no. Here are some videos of buildings collapsing naturally:
Granted these buildings are smaller, but they are still big. All of them failed in part but in many ways held strong until the end. Most incredible is the last video.
For the record, none of those except number 4 collapsed. They toppled. Number 4 collapsed in exactly the same way the trade center buildings did, but the weight of the collapse just wasn’t enough to crush the entire building.
I'm not a conspiracy theorist, but have always been puzzled by video of WTC collapses. Having a background in steel fabrication and familiarity with ANSI, ASME and NIST governance thereof, my first thought is, steel doesn't behave like that. It takes a lot of heat to lower the yield point in such a short period of time.
Building 7 had internal fires for hours, though. Given elevated temps and thermal expansion weakening joints and turning columns into beams, such an outcome is inevitable though surprising.
Now that I've admitted being a traitor, can I get a bumper sticker instead of a T-shirt?
No, if the oxygen were consumed it would simply be replaced by smoke and carbon dioxide. The pressure inside and outside the building would necessarily be equalized. Air pressure in any case wouldn’t make a significant difference in the collapse speed.
First, the fires were mostly lower in the building. IIRC, floors between 6 and 14 or so had the heaviest fires, out of 47 total floors.
Next, your expectations aren’t based on what really happened. A large building like WTC7 couldn’t topple, because it’s engineered to support itself when standing upright. Tilt it a little bit and the forces on the strained structures are way larger than what they can support.
Alex, the building obviously had a major internal catastrophic failure six seconds before the collapse started. The structural supports were already strained.
This is QUITE enough. This is Great Debates; if you want to fight ignorance, do it here; if you want to flame ignorance do it in the Pit. Everybody chill out a bit.
[Moderator Hat OFF]
Particularly questions about how fast the building came down (compared to free fall) and why it appeared to come down symmetrically. Please take a gander and see if that helps.
In previous WTC threads I’ve offered my opinions on certain technical issues and those are based on my education - I have a BS and MS in structural engineering from UIUC (one of the top CE schools in the country). For folks who are making statements about what is and is not possible on technical issues may I ask what your education or work background is in the related fields?
Carson, for example, you mentioned you’ve done steel fabrication work. Alex, how about you?
Carson, as far as heating steel goes: Structural steel loses about 50% yield strength at 600C (about 1100F). It’s metal and will heat up very quickly. At lower temps the loss of strength isn’t so catastrophic but thermal expansion can result in major stress as the structures geometry changes - joints could break, beams and columns can buckle.
