Sorry, NIST does not talk about falling floors in its report, it is just excess energy applied to and too little strain energy in the structure below to absorb it! NWO physics!
No
"NWO physics" to speak of, it's not rocket science. If you're talking about the entire lower structure as a unit then look at the collapse, no part of the lower structure begins to yield until the collapse threshold reaches it. The failures occurred individually in rapid succession, that's exactly what a progressive collapse is.
From NIST report - NISTNCSTAR1-6D chapter 5.2 - we learn:
"The aircraft impacted the north wall of WTC 1 at 8:46 a.m. … between Floor 93 and Floor 98. … The subsequent fires weakened structural subsystems, including the core columns, floors and exterior walls. The core displaced downward … At 100 min (at 10:28:18), the north, east, and west walls at Floor 98 carried 7 percent, 35 percent and 30 percent more gravity load loads … and the south wall and the core carried about 7 percent and 20 percent less loads, respectively., … At 10.28 a.m., 102 min after the aircraft impact, WTC1 began to collapse. … The release of potential energy due to downward movement of the building mass above the buckled columns exceeded the strain energy that could be absorbed by the structure. Global collapse ensued."
I don't know what what you're reading off of this, but this section says nothing about treating the
entire lower portion of the structure as a single structural unit, as you're treating it. The lower section did not fail all at once, the only viable collapse progression there was were the floors failing one after the other progressively along with every other part of the building. The collapse videos show large sections of the core structures remaining after everything else had failed around them, it's fairly straightforward that the progression does not exhibit the behavior you propose.
NIST forgets to calculate the potential and strain energies and explain why global collapse should ensue. A lot of potential energy will just be diverted away by the structure below ... and not applied to it.
They have. They've calculated that a single floor could sustain itself, and a static load of 11 additional floors; under a dynamic load a single floor could sustain the weight of itself and 5 additional floors. In World Trade center one the dynamic load consisted of roughly 15 floors, in tower two this was roughly 29 floors.
In a progressive failure you don't have all of the structure failing at once, the upper sections are falling as a unit and then exerting all of that potential energy it had as kinetic energy onto the floor below, and this mass increases as the collapse advances. Your analysis leaves this out.
Furthermore, if an impact occurs, it is columns against columns according to Bazant (and floors shaking loose).
In my analysis (if impact occurs, which is not proven) it is columns against floors at contacts, with the columns destroying the floors with collapse arrest as result - damaged floors getting entangled into one another, etc. This has happened often in structures due overload.
It has nothing to do with floors failing at single points and then hinging downward like a trap door. That's an awfully strange assertion to make particularly when one has the entire top section of the structure coming apart, and not simply an interior set of floors.
It has everything to do with the fact that a 15 to 30 floor section of the building just slammed into a single floor with all of it's weight which was more than the individual floor could handle, this transfer of forces did not fail the entire lower section as a unit, it failed it progressively where it was weakest.
Complete top section against one floor is not possible at first impact - the columns are in the way! And the top section is not very strong - 95% air, 4%floors 3.7 m apart + misc, and <1% columns spread around. Top section will be destroyed at/soon after impact (with columns) and the destruction is arrested.
Once that top section was in motion and imparting an entire array of moment and axial forces against whatever was still intact within the impact zone that ratio of empty space to solid mass doesn't make a helluva a lot of difference in whether or not the structure is sturdy enough to hold the building in a static vertical load, all of the forces enacting on the structure from this point forward are dynamic. I would think the columns would be the least of your concerns, particularly considering it was the connection points where two column sections met that suffered the most common failures. As an engineer of any callibur even you should be aware of this.
connection failures
