Some Misunderstandings Related to WTC Collapse Analysis

[Tony Szamboti]

Tony,

Would you mind summarizing you position in non-technical language if you have the time-- if that is possible. I have looked through your paper and find it tough sledding.

My experiences with JO have been less than rewarding on a number of accounts.

Lauren, the columns below are designed to support several times the load above them for safety. In order to cause them to yield, and start to collapse, the upper section must fall on them from a height and generate what we call a dynamic/amplified load. This requires deceleration which there is no indication of in the measurement of the North Tower descent. Jeffrey will argue this, but he is taking the word of one anonymous poster who claims he measured a deceleration. Nobody using their real name has found any deceleration in their measurements. Now not only does there have to be a dynamic load to start the column yielding, but there has to be enough kinetic energy available to completely collapse the column, because as the column deforms it absorbs energy, and in the case of large steel columns lots of it. The fall of the upper section of the North Tower should not have progressed, because the column energy absorption capacity was significantly greater than the kinetic energy that was available. In other words, there wasn't enough energy available to break through the columns after a one or even two story drop. The reason Zdenek Bazant's analyses showed there was enough kinetic energy to break through was that he grossly overestimated it, by using a much larger than actual mass and having it fall faster than it actually was before impact, while also grossly underestimating column energy absorption capacity. We were able to show he was completely wrong with his available energy to energy absorption ratio now since enough details are finally publicly available about the actual weight of the building, the column sizes and grades of steel, and the measurements showing the actual fall velocity. When Bazant's calculations are redone with the correct parameters the collapse arrests after a one or two story drop. This means the columns were not involved in the collapse. We don't come right out and say it in the paper, but there is no natural way for that to happen. I apologize for the single paragraph as that is all the site lets me do while on my home computer.