I'm saying the opposite. You need the verinage to crush the load-bearing elements in that concrete structure, but for the WTC towers, that wasn't necessary and provably did not happen (I linked to pictures of the spire and the fallen facade). To collapse a steel frame, all you need to achieve is to destroy the connections.
Did you see any of the earlier discussion of how this relates to a type of demolition called verinage? In those, the top 50% of the building is used to crush the lower 50%. But you seem to be saying that in the case of the WTC towers, something like the top 5% might even be sufficient. What makes the difference in your opinion?
why are you ignoring the fact that these are different building types, and that load-bearing columns in the WTC towers were not crushed? You've seen the pictures.
So what mechanism are you saying "destroyed the connections", specifically in the core of the towers? It was the weight of the upper floors bearing down on them, right? Would you use a different word other than "crushing" to describe that?
It were the connections between the core and the outer facade which were failing. The cores were mostly destroyed by gravity I would say as Mendel has shown in other posts he linked. ( https://www.metabunk.org/threads/ho...he-twin-towers-to-truthers.12072/#post-259237 )
"shearing", probably.
The WTC towers have the core columns, the "hollow box" facade columns, and the floors between them bracing them. The floors connect the core to the "outer facade", and once the floors fail as the building progressively collapses, all these columns are no longer braced properly and topple easily.
It's the "structure" of "anything" that resists gravity... and "gives shape" to things. The structure of the buildings like most other high rises is a frame of steel and steel reinforced slabs. ROOSD was notable because the axial structures were bypassed and the collapsing floor mass gutted the buildings. But the ROOSD began as a result of failed axial members which "freed" the upper block mass to drop and crush the lower block. The typical floors were not designed to support more than perhaps 3 or 4 floor masses.... so once started the building self destructed floor by floor. 7WTC's demise came after the axial structures low in the building were destroyed as a result of a progression of toppling of transfer structures leading to column failures leaving the top (floors, facade/moment frame) with no support. It crushed floor by floor from the bottom during the collapse. Facade and moment frame were likewise destroyed as the collapse down with no support.
ROOSD is an acronym for Runaway Open Office Space Destruction.
Before someone says this is shoddy design, remember you could fill up a storey completely with water and not exceed the total strength of the floor connections. It took a catastrophic event to trigger this runaway collapse.
The loading was dynamic not static.
It wasn't shoddy, but it was not as robust as the Empire State building.
Even the Empire State couldn't stop an aircraft engine from crashing out the other side.
It is drifting off topic. The issue is how high up the tower can a plane crash and still cause collapse. Stick to that.
The OP question is: "How high could the plane have hit, and still caused a total collapse?" and I don't think the discussion is as far off the topic as it may seem.
) sure that progression would lead to global collapse IF we could trigger "initiation".
with unknown differences in the aircraft impact damage, as the facade and core columns are less sturdy higher up.
Yes. But the net result is it either will or will not trigger progression. And anything other than the "ROOSD" process we saw on 9/11 will arrest.
Possibly true. But my point is that the net result dominates the OP question. Anything OTHER than a "ROOSD" style progression will halt. AKA "not cause a total collapse".
Yes. But the key question remains:
I've been wondering if it would be possible for just half a floor to come down, like if the "hat" breaks in the middle and one half comes down? Intuitively, I'd still expect that to progress, and possibly "eat" inward and over to the other side as it avalanches down, but is that realistic?
Seems to me that a partial floor collapse would radiate/spread throughout the floor plan because there was no structural isolation of bays. If the break was very clean perhaps it would not spread... but the floors were composite with rebar and long metal pans.
I've given it some preliminary thought - it may not be possible to come to a definitive conclusion.
So let's imagine that somehow a small area/concentrated 10,000# load dropped on a WTC floor. I imagine it would punch through the floor, destroying at least a portion of the floor around the impact... and the load would continue as unstoppable until it hit the ground. The question really asks if a large area load which exceeded the floor spec would radiate throughout the floor or simply cause a runaway local collapse.
Econ41 uses the image from 2WTC. 1WTC did not as much tilt.... It does seem to laterally translate causing misalignment the column ends, However these column ends were staggered over 3 floors as far as the facade is concerned. And the column ends of the core were not at floor level...nor were the facade column joints aligned with the floor slabs.
That's pretty much what I've been wondering.
True.
Yes there is "macro" level AKA overall lateral translation but it is also irrelevant. Or more pedantically stated - it is redundant. Think from the micro. Many columns failed and in doing so they got shorter overall (the Top Block was differentially moving downwards. So for each individual failing column as it got shorter the ends must be missing or bypassing. The gross, macro level, lateral translation comes later as a consequence.
I'm not sure of the relevance of this detail.
The cores of the Lower Towers of both Twin Towers were dismantled by a process analogous to ROOSD << which, strictly, refers to the open office space i.e. "OOS"
That is far too ambiguous. What was falling was, in the early stages, the Top Block as it was breaking up in mutual destruction with the top of the Lower Tower. Later, in "established progression", it was the accumulating and increasing weight of debris. Never the "weight of the Upper Floors" pers se or in any overall sense of the upper levels still being intact.
"Shearing" is technically correct had appropriate.. The word "crushing" has a bad history of confusion and is simply wrong EXCEPT when applied bodily - at the "macro" level - e.g. your other thread references to "soda can crushing". An applied weight bodily crushes the whole of the soda can. We are not dealing here with an imagined "large boot" crushing the whole structure of the Tower. And there is no buckling involved at this stage. "Shearing" is the dominant process.
the steel columns were tapered
17 floors weighed more than enough to drive the progressive collapse
Very simplistic drawing below.
| This is fine | This is not (and it's not a problem with the nail being too weak) |
You think it is just a matter of aesthetics?
