The 9/11 Forum

femr2 --- WTC 7? Are not we doning WTC 1? Yes, I have made several points regarding possible sources of what the wideo recorded, none of which require any form of "pre-collapse". Further, you need to specifiy a hypothesis and then determine the RMS error for each such hypothesis. Here are...

By scrubbing through the video you can see the movement for yourself in a better form than any amount of written analysis. But then fail to interpret it properly. The high frequency component is mostly noise. I agree. Properly using the tracking of a nearby (and static) feature should elimnate that...

femr2 --- By actually reading NCSTAR1--2A you will discover there are torquing modes; rotations at the top.

Double static points are the means to see the movement, so no, not camera.

Explain please. I don't seem to be following this.

Interesting, but consider the breeze blowing from generally the NNW that day. The high frequency component is likely due to the tripod and the camera with its heavy telephoto lens hanging out in front. The lower frequency camera shake might just be due to a breeze gust, or nearby HVAC motor starting...

T_Szamboti --- Consider your leg pulled.

Of course it was natural.

Nothing supernatural about it.

Niclas --- Depnds upon the location of structural steel members in the crushed zone. Extra time certainly won't make a difference; it is only whether the applied load is (eventually) sufficient to break connections and comminute concrete, etc.

Niclas --- Splice failure observed almost everywhere. After initiation nothing was coaxial and structural steel slammed sideways into structural steel below, snapping the splices. Think of the zone of crushed amaterials as similar to a flowing snow avalanche; roiling.

Scale models can be used for statics questions, since the loading mass can be made appropriately small. For dynamics, consider Galileo's studies of terrestrial gravity using cylinders rolling down inclined planes. Another reason for thinking of WTC 1 collapse as a vertical avalanche as the study of ...

psikeyhackr --- Read Bazant & Le, available from Professor Bazant's publications page. Under the stated simplifying assumptions what is claimed indeed follows and of course follows the 3rd law. The only possible question is the estent to which the simplifying assumption acutally apply to WTC 1 ...

Niclas --- One column butting on another is not the same as solid steel.

First Greening, then Bazant with co-workers have provided quite a reasonable description of the progressive collapse. Have you seen any model by which their theory can be reproduced in physical reality under experimental conditions? If not, what rationale could one have to claim their notions could...

Doesn't a skyscraper have to have a disproportionate amount of steel and concrete in its foundation and lower portions to withstand the wind? No, to withstand the weight of the upper portion. Therefore the strength must grow, downwards, in arithmetic progression. So Greening's calcs were based on a...

Thank you for clarifying David, we seem to make some progress. You are welcome. Did you read what Mackey said in the exchange with me i posted earlier? Do you agree with him? I didn't follow that closely but he is a fine engineer. Like i said in my comments, how can one storey, or let us say one co...

Major_Tom --- Thank you. Ok, about 0.6 m of sag due to increasing tertiary creep in the core.