Quote:
Originally Posted by JThiessen
Response to the techincal statements only:
The steel did not have to melt to achieve that kind of failure. Jet A fuel burns on its own at @500-600F, but add the heat of whatever other combustibles were present - likely temps were in the low 1000 degrees in places, and potentially higher in others. Those fires burned for what 90 minutes and 120 minutes? That long term heating of the steel would have brought the strength down, likely by half its rated capacity. Combine that with the impact damage, and you have catastrophic failure.
The buildings design is likely what kept them falling basically straight down. They had a grid structure that completely surrounded the exterior of the building (remember the ghostly looking grid structure pics). Those were what resisted the lateral loading of the tower. The vertical loads were supported by an inner structure. And that is what was unique about these towers - neither of the load paths shared duty with each other. So when that one or two floors inner structure finally reached the point that it couldnt hold the weight of the 50 floors above it, it basically pancaked its way down, with the external grid acting almost as a guide. Technically feasible. To have it happend twice is also feasible as the cause of the events was almost identical.
Since there have been links to other sites, here is one on the structural analysis. Very clear and concise IMHO.
http://wtc.nist.gov/pubs/factsheets/faqs_8_2006.htm |
Ah, never thought about the fire bringing the steel structure down (in terms of temperature to melt)...