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| Re: Building Const. For Fire Service (Was: Some WTC Thoughts) (348077) | |||
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Re: Building Const. For Fire Service (Was: Some WTC Thoughts) |
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Posted by JayZeeBMT on Tue Aug 26 16:16:40 2008, in response to Re: Building Const. For Fire Service (Was: Some WTC Thoughts), posted by JournalSquare-K-Car on Tue Aug 26 15:49:26 2008. Taking your last assertion first, the fires in both towers were fed by both jet fuel and any combustible materials ignited upon impact of each plane. Long-term exposure to continuous high temperature environments will aggravate existing structural damage to a building. The "shock load" generated by the impact of each plane was, again, in excess of what the towers were designed to typically withstand. That the towers stood as long as they did argues for the quality of their design, not against it.As for your further assertion that in a controlled demolition, only the upper floors needed to be destroyed, "sloppy" though that would be, let's refer to Brannigan once more. In a "progressive collapse" which is what actually happened to both towers, the surviving columns and load-bearing trusses on each floor failed as gravity began to work on their damaged sections. Brannigan follows Newton in concluding that the entire live load of a building must be delivered to the ground. Put another way, the energy needed to bring the structure down is stored in the structure itself, until acted upon by an external force (like an airplane). If a controlled demolition of only the upper floors is attempted, there would be pre-collapse shock loads delivered along the outer columns directly to the ground, resulting in a partial demolition. For controlled demolition to work, explosives must be placed throughout the building. The aircraft which struck the towers were much larger and heavier than a 707, and flying at cruise flight. The WTC designers ebvisioned a scenario in which a 707 struck a tower while attempting to land or take off from JFK. This of necessity meant they were anticipating a slow-flying aircraft, not planes traveling at high Mach components. As for the towers' rate of collapse, the time frame is consistent with a progressive collapse and Brannigan's Law. (In a structural collapse, the breakup of the individual load bearing members allows them to fall to the ground individually and independently.) You can see this principle illustrated very vividly in footage of the WTC 1 collapse, as the outer columns fall away from the building separately. WTC 7, as I stated earlier, was severely, severely damaged by the collapse of its neighbors, but managed to remain standing in failure mode for another 7 hours. WTC 7 did NOT, by the way, collapse onto its footprint. It appeared that way from TV footage, but in reality, debris from WTC 7 was recovered as far away as the E10/L10 firehouse adjacent to Liberty Street, almost 500 feet away. A small, but telling fact: The IRT Cortlandt Street station remains closed to this day because of the volume of debris which collapsed onto it, actually knocking the tunnel alignment out of true by almost two degrees. That's because the upper columns hit the station by an offset of almost ten degrees from vertical as they failed and split off from their trusses... |
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