North Tower Acceleration

[William Seger]

165. Again: Why Chandler is wrong

> So now, do you disagree with Chandler's statement that "as long as the top section of the building is in uniform downward acceleration, it cannot possibly be providing sufficient force to destroy the building." ?

There are three problems, actually:

1) Chandler merely assumes that the top section of the building was in uniform downward acceleration, without proof and without ever explaining how that could possibly happen even in a controlled demolition. His logic is that it can't happen in a "natural" collapse so it must have been an assisted collapse -- his desired conclusion -- thereby missing the most obvious and more likely explanation: uniform downward acceleration is just not what was really happening.

2) Local decelerations could be happening in the collapse front without being noticeable at the roof because they are very brief and the flexibility in the structure doesn't allow the deceleration to propagate all the way to the roof. Szamboti says that if that were the case, then the flexibility would also mean that not all of the kinetic energy of the top section could be applied to the lower structure in the collision because some would go into flexing the structure. That's quite true but it misses the point that we are talking about a situation where the top had much more energy than was necessary to collapse the impacted columns, so it wasn't necessary for all of the energy to be transmitted at the collision zone.

3) It IS in fact possible for the top to destroy the bottom without any deceleration, by attacking the supporting columns individually or small groups rather than all at once. This was the point about Szamboti's "missing jolt" that he refused to see: If all the columns were reacting to the collision at the same time, then yes there should be a jolt because some "load amplification" would be necessary to collapse the columns, which would be seen as a deceleration. But if the top was tilted when it impacted the floor below, then the columns would not be attacked all at once. If the effective mass bearing down on one column or small group of columns is greater than they could handle as a static load, then no "load amplification" is necessary to collapse those columns, and there would be reduced acceleration but no deceleration. It is conceivable (although unlikely) that with a tilted top, such a condition could progress across the building, sequentially collapsing columns without ever encountering enough resistance at any one time to decelerate the falling top. As unlike as that scenario is, the effect of the tilt is that any "jolts" would be much less than what Szamboti calculates by assuming all the columns resisted at once, and they could be small enough that they would be undetectable by the fairly crude method used (measuring pixel displacements in fairly low resolution videos.)