Since it has been nearly 7 months since we left off, I had to go back to re-read the points brought up earlier. I apologize for quoting posts previously written, but since no rebuttals were made, their contents are still game for debate.
Posts #44 and #46 contain a healthy deal of information, but some summaries are:
From Post #44 (2/04/08):
Quote:
Originally Posted by Byrnison
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[detailed observations about fire progression in WTC7, building codes for "ordinary building fires", pictures from WTC 5, and steel temperature/strength curves]
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Putting together the observations: - Fires began burning after the fall of the twin towers.
- The fires in WTC7 were not fought by fire fighters, and spread over approximately 7 hours.
- Over time and without sufficient cooling sources (water, air) fire temperatures can weaken steel.
- Available data from testing standards, flame temperatures, and NIST computer modelling indicate that temperatures of at least 500-600C are possible.
- WTC 5 contained regions of collapse due to fire damage in the interior of the building, regions in which cooling sources can be expected to be the weakest.
- WTC 5 showed evidence of steel failure due to excessive temperature, but the loads were distributed to other columns and prevented global collapse.
- WTC7 collapsed internally first, at the East side of the building, an area in which fires were seen to progress throughout the day, and again in an area in which temperature would be expected to be highest due to lack of cooling sources.
- WTC 7 had a unique load distribution scheme in floors 5 to 7 - the columns did not extend straight from the ground to the roof.
- Evidence seems to show that after the East side interior collapsed, there was a delay while the load was redistributed, then the interior collapsed from the East to West, pulling the facade down with it.
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from Post #46 (2/12/08):
Quote:
Originally Posted by Byrnison
...[examples of buildings that failed in fire situations]...
Obervation seems to suggest that any building, if on fire for a long enough period without adequate fire fighting capability, *can* collapse, at least partially.
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from Post #51 (2/13/08):
Quote:
Originally Posted by Byrnison
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When you do get back to it and have a chance to read the posts regarding the fires, I'd be interested to know if you still rule out fire as a credible collapse initiation source. Initially (before posting), I thought that severe damage might have played a primary role, but after researching the information (especially for posts #44 and #46), I'm thinking that the fire may have been the cause, and that the damage played little or no role at all.
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and finally from Post #54 (2/14/08)
Quote:
Originally Posted by Byrnison
...I am happy to re-evaluate or defend my reasoning should observation/evidence that represents a higher probability be presented.
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I understand skepticism could exist were there higher-probability scenarios to the observations provided, but to this point none have been forthcoming. To me at least, the NIST change of position that fire itself was the cause of collapse (and not the building damage) for WTC7 is something that seemed reasonable nearly 7 months ago, and it is interesting to see that it is now currently the leading suspect after NIST's analysis as well.
Without rebuttals and/or competing evidence to the many pieces of information brought up in those previous posts, I am uncertain how to continue the debate.