Reply #128: There are quite a few problems with Ross's analysis...

[Carefulplease]

http://worldtradecentertruth.com/Journal_5_PTransferRoss.pdf

I have commented already briefly on this paper. You can search the archive. Here are some further comments.

In this analysis of the energy conditions for the sustainability of the collapse of WTC1 Ross grants that one floor failed and that the upper block of the tower (16 storeys) fell freely 3.7m and impacted the lower section of the tower. He then calculated an energy balance of the process that occur until .02sec after the impact and he concludes that the energy available is fully spent and the collapse can not proceed. His analysis is flawed in several respects.

(1) The very model he uses for his whole analysis is flawed. He assumes that after the upper block has fallen from the height of one storey and has impacted the lower section of the tower there still exists a perfect mechanical coupling between the upper and lower segments of corresponding columns. But these columns -- in a realistic scenario that grants the conditions of collapse initiation -- have already buckled or failed at the splice. It is mostly the upper floor of the lower section that will resist the fall of the upper block. This does not provide the coupling Ross needs to sink the kinetic energy of the block above in the strain reserve capacity of the columns below and above. Ross would rather require, it seems, that 287 column buts below fuse impeccably with 287 column buts above so that the columns load bearing fuctions and strain absorbing capacity be fully restored.

(2) Ross also assumes that after the collision the momentum distribution in the storeys below ranges linearly over a distance of 24 floors below the impact level. Conservation of momentum then dictates that the velocity of the upper block is reduced from 8.5m/s to 4.8m/s and the 25 storeys below acquire velocities that range linearly from (23/24)*4.8m/s to zero m/s. This assumption begs many questions as it builds into the model the assumption that the tower is a giant spring that can absorb the shock of the falling upper block without damage. But the assumption is physically unrealistic. For one thing, it ignores the inertia of the floors and the relative weakness of the floor connections to the columns. This process is supposed to last 0.02sec. This implies that several floors just below and above the impact undergo accelerations or decelerations close to (4.8m/s)/0.02s = 240m/s^2 or 24 times the acceleration of gravity. The only way that I can see to make the model more realistic is to vastly reduce the number of floors involved in the energy absorption during the collision process and this changes the energy balance in a way that is fatal to Ross's argument.

(3) Another major blunder is to count the kinetic energy removed from the upper block after the impact as net energy expenditure in the energy balance. Some fraction of this energy translates into kinetic energy of lower storeys. The rest is "lost" to the extent that the collision is partially inelastic. However the former still is available to produce damage down the road and the latter already *has* been expended doing such damage. In short Ross counts the amount of money spent as a further expenditure and thus he counts it twice!

I have other minor quibbles but each on of these flaws seem sufficient individually to compromise Ross's conclusion that the collapse ought to be arrested.

As an adendum, if you want to read the paper carefully take notice that many occurances of a mysterious factor 10 appear to be typos when some factor 1000 (or .001) is required instead. I am also unsure avout the last "/2" in the calculation of the "Compression of impacted section = 24MJ". There also seems to be some confusion at time about wether 16 or 24 storeys below the impact point are being considered. There are further minor issues.