I agree with the post above. However taking out a bunch of columns will be much more difficult than it sounds. Columns at the lower levels were W14x730 or larger and these have 4.9in thick flanges. So I hope Hulsey will try and explain how they could be easily cut without noise.
Not sure I understand the thermite idea either, because melting a 5 in thick steel plate that is predominantly in compression is only likely to squish it under extreme circumstances.
If we assume that the US military had plenty of time to study the WTC7 plans, ( which is what is implied by Ae911truth ) as they would have had to have time to develop the silent explosive as well as plant them, make sure the WTC tower was designed to damage WTC7 , as well as start the fires and knock out the sprinklers.
So how many of the infinite variety of demolition options do you think Hulsey will look at. ? And how many parameters they will look at.? Rapid collapses can cause large dynamic load amplifications and slow collapses don't so I would expect thermite to be slow and explosives fast. Lots of other variable in loads, tolerance, damage patterns could have big impact in outcomes. I hope they look at the following options:
1. The low cost options: Demolish the beams coming into Col 79 to get a cascade failure of the beams below. If one level doesn't work try several. And what assumptions would one have to make, to cause a collapse and are these assumptions unreasonable.
2. The col 79 option. This is the NIST preference. Would be interesting to see what Hulsey makes of it.
3. 1&2
4. The transfer column supporting transfer truss TT1. This would take out 4 superstructure columns.
If that doesn't work then add the Column supporting TT2
5. 3&4
6. All the interior columns. This is the scheme implied by Ae911truth. Lots of thermite, pyroclastic clouds, pools of molten metal, straight down and free fall accelerations
I think we should discuss what Hulsey would need to do to develop his hypothesis. The tests and analyses outlined above are the minimum amount of analysis that Hulsey would need to do, to demonstrate his claim that fire could not have brought down the buildings, and it had to be a CD.
Analyses 1 and 2 gets to the very essence of the disagreement between NIST, Weidlinger, Arup, Thomassetti, the rest-of-the-world on one side and Ae911truth on the other.
Analysis 1 is important, because there are many reasons why a beam or floor could have failed. And there are many examples of beams failing in fire in tall buildings and even in small buildings. WTC5 was a great example of fire induced floor failure. Most of the specialists only take the WTC7 analysis as far as beam failure, because once the beam fails the assumption is that the rest will go. But if Hulsey can prove that the assumptions needed to get beam failure to cause progressive collapse are unreasonable then that will help to justify his theory.
The reason that the parametric analyses are important is to determine what variables are important. As with all conventional non-linear collapse analysis, the speed of impact will be very important for determining ductility and dynamic amplification effects. The ductility of the joints is also a primary variable. While the beams above the burn-out floors could be quite ductile, we know that in the floors below, say level 12, the floors have burnt out, the beams will have expanded, locally buckled at the end, and will be in the cooling phase, so the bolts will have large tensions in them… not a good condition to resist impact loading.
Its important to generate a progressive collapse and then see if the variables you have assumed are unreasonable rather than doing an analysis and saying… "
see it doesn't collapse". Doing so proves that you have the capability to generate and modify the collapse sequence. And once collapse starts it becomes very difficult to control the sequence and you can image that there are millions of interaction so an impact a half a second later or 4 inches to the right will effect the millions of subsequent interactions.
Once you get failure of beams around Col 79, its not clear to me if the connections to columns 80 and 76 , would be ductile or if they would shear. If they shear you get progressive collapse of Col79 below the fire. The next stage is the column becomes slender, stripped of its floors, reaches its compressive capacity, starts to buckle, turns into a tie and hangs from the upper level… at this stage the penthouse will sag as the floors try and act as a catenary to span between adjacent columns. If Hulsey can prove that the beam connection parameters that you need to assume to get progressive collapse are not consistent with a post fire ductility then he is a good step on the way to proving that fire induced beam failure would not cause the collapse.
The second analysis is column removal. Failure of large columns in fire is less common than failure of beams however lots of precedent of column failure in fire. So how can he prove that failure of col 79 does not lead to a global collapse? If he can prove that the assumptions that you need to make to cause collapse are unrealistic then that will also help to prove that fire induced failure did not cause the collapse. This analysis will be interesting because he will also have to prove that the sudden load transfer to adjacent columns would not cause failure of the columns or transfer beams.
