Tony Szamboti Wrote:I don't believe what you are contemplating is possible for several reasons.
1. The only mechanisms acting on a building which can provide lateral forces are wind loads and seismic loads and a building would be designed to handle these without shifting between floors.
If the building were designed in a certain way with an inner core and outer frame as the Twin Towers were the force of the floors falling within this contained cylinder would create a funneled air force similar to compressed air. Compressed air, when channeled correctly, can possess enormous force. All you needed in this situation was enough force to shift the hanging truss supports away enough to release their support and you had a real problem. This compressed air force would have blown laterally and shifted the inner core inward pulling the floor support out from under the truss and unzipped the outer frame outward, also pulling the floor support away from the floor truss. A concrete floor pad is basically a big heavy air compression ram when left to such a channeled confined space and gravity. The initial impact of the first floor collapse and lateral air blast could have been enough to compromise the inner core's vertical resistance. If this occurred you have failed to acknowledge the serious acting force of this lateral air blast and its effect on the inner core. It is possible it was strong enough to buckle it inward instantly, in combination with the mechanical force of steel members also pushing it laterally, which would completely destroy the vertical resistance to which you refer. Meaning it wasn't there and the inner core was being blasted apart and falling in tandem with the collapsing structure. Your statement above is instantly rejectable because what we are talking about is the split second dynamic occurring within the structural failure and the forces of that failure. To enter a textbook view of normal lateral forces on buildings is to show a lack of understanding in my opinion. What counts here are the forces that destroyed the building as it occurred. What you wrote above is untrue simply because the "mechanisms" we are talking about are those that occurred from a major insult to the normal integrity of the building caused by flying wide body aircraft into them.
Tony Szamboti Wrote:So I don't know where the lateral force required would come from and how it could accomplish what you are saying. It would have to be applied to only the upper section and would have to be enormous to shift the upper section due to inertia and with its columns still connected to the lower section.
Video of the South Tower showed a bulge in the outer wall in the collapse area that very obviously occurred at the impact and fire zone. The deceleration actually occurred at the beginning where both Towers slowly eased in to their collapses.
The North Tower probably had some serious inner core column damage because the Boeing hit square in the middle. I feel you've got the science backwards because the static resistance you cite would have resisted the collapse as you say. So you have to ask why it didn't? One solution would be controlled demolition devices. I doubt they were thermite because thermite burns with sparkles and smoke. If thermite were placed I think the firefighters present throughout the building would have noticed it and reported it. Remember where the staircases were. Also, why would they pull the South Tower first if it was hit last? In my opinion the fact the North Tower fell tells you something overcame that vertical resistance. I believe it was a lateral force caused by the unique design of an inner and outer frame that didn't have enough lateral cross bracing to resist the forces of collapse once initiated. The building's engineering relied on the floors themselves to act as this cross-bracing. Once any section suffered critical damage from airplanes being flown into them and burning this design was a fatal flaw waiting to happen. It would not be in the government's interest to admit it killed thousands of people with this flawed design.
Tony Szamboti Wrote:2. The columns would not buckle after losing support for one story. They all could go at least three stories without lateral support before buckling. It is hard to see how this contemplated shift could ever be sufficient to dislodge three stories worth of floors from their vertical supports. The shift would have to be massive and even then it would only potentially separate the floors from their vertical supports in one direction, since it would only affect the floors that are normal to the shift not those parallel to it. What would really need to happen, for what you are contemplating, is for the core to shrink in girth and the exterior to expand. That is even less possible than the shift.
They might if they were seriously cut by the Boeing impacting them at several hundred miles per hour. The outer frame gave way upon impact and was cut through by the incredible mass of a Boeing impacting the building at full throttle with fuel tonnage in the wings and the longitudinal strength of the fuselage. The open cut-out of the plane in the impact zone proves this. This mass traveled forward and probably severed many of the inner column members. To say they wouldn't buckle is to ignore the serious damage they obviously received. Again, I feel you are failing to observe the real situation and referring to technical theory. Besides, I'm not really sure what you are talking about because even the North Tower had at least 11 floors above the impact zone. If this mass hit the first level of intact inner core the force we are talking about would be 11 floors of mass hitting the lateral resistance of one or two floors of core column. It is this inward lateral force you have failed to account for in your analysis.
I totally disagree with your claim that the outer frame could not expand and the inner core shrink. If you look at the dynamic I spoke of that is exactly what would happened as super compressed air escaped from the falling concrete floor pad in the path of least resistance, which would be the hollow of the inner core and weaker resistance of the outer frame which was supported by nothing but air behind it. Indeed, if you look at the videos, the outer frame peels back exactly in this fashion as the building collapses. We are not talking "shrinking" here we are talking blasting inward from air blasting from the falling floor platforms and physical members. Something those column members were not designed for.
Tony Szamboti Wrote:3. For the lower section columns not to provide resistance to the fall of the upper section their lateral support needs to be completely removed before the upper section hits it.
This would happen instantly as the air blast descended with the floor pads. The outer frame would be unzipped and the inner frame blasted inward destroying its structural integrity. I think you are talking floor trusses as far as "lateral support" by the way.
Tony Szamboti Wrote:4. The core floors would not be susceptible and the core was self supporting, so it would not fall without providing resistance.
I don't know what you mean by "core floors"? I believe I just showed you why the core would blast inward and remove support from the floor truss supports. This would quickly become exponential as the falling floor mass accumulated.
Tony Szamboti Wrote:I would say what you are contemplating would be on par with a magic trick. It just has no basis for occurring in reality.
Very practically possible in my opinion.
Tony Szamboti Wrote:The paper is about the North Tower. If there is a serious problem with it then it is not hard to imagine a problem elsewhere.
The South Tower had more mass above. There was probably a slightly different failure there that involved the core buckling because of the tilted nature of the collapse. However in less than a second the same dynamic must have occurred.
Think of a pop gun and how ramming air in a cylinder quickly creates an explosive force.
