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Post by feelfree222 on Apr 22, 2007 23:35:05 GMT -4
What they found was that the foam worked well to do it's job, unless there was some missing, and then the metal heated at the missing spot and transfered that heat along its structure. More later. wtc.nist.gov/pubs/NCSTAR1-6ExecutiveSummary.pdfNIST also observed that... However, the temperature rise quickly dissipated as the distance from the gap increased. Because there was insufficient information about the location and occurence of the gaps from photos analysis ,insulation gaps were not considered in the thermal modeling see Passive fire protection for structural components
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Post by PhantomWolf on Apr 23, 2007 1:04:08 GMT -4
see Passive fire protection for structural components
That's what I am reading at the moment. As to the gaps, are you going to suggest that the fireprofing was entirely intact after the impacts?
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Post by feelfree222 on Apr 23, 2007 1:09:37 GMT -4
see Passive fire protection for structural components That's what I am reading at the moment. As to the gaps, are you going to suggest that the fireprofing was entirely intact after the impacts? No,but because they have not enough evidence about the occurence(how much) and locations they choose to not include gaps in the -tests- and simulation model of floors support systems. Read the executive summary you will save a lot of time. Edited to add Remember the NIST floors tests assembly model is based on 0.75 fireproofing thickness.Rather than the 2.2 inch average thickness following the upgrade in the 1990.
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Post by PhantomWolf on Sept 6, 2007 18:20:14 GMT -4
Okay I admit I have been really, really slow getting back to this, one of the major problems with getting distracted by rl and other things, but I did say I'd get back to it, and I so I am.
Hopefully feelfree222 is still about and reading these.
Okay so to the Tests.
So the major question was. "Why did NIST only use 0.75 inch fireproofing in the tests."
They did that because that was the initial standard. The tests on the truss assemblies were to determine if the original as build truss designed were actually up to standard. Because they couldn't find any information on the original testing, they decided to conduct their own testing and find out. Thus they set up the tests to conform to the original specifications.
As far as their own modelling, they didn't use these results at all. They modelled the fullsize trusses in the computer to see what would happen with the removal of fireproofing under various conditions. This makes a lot of sense really because it means that once they had verified that their model worked, they could run dozens of simulations with differing fire proofing thicknesses and damage rather then having to build and test a unique assembly for every test they wanted to run.
From this modelling that were able to gain a rough idea as to how the building would ract to the fire, though even they admit that due to their lack of information about what was occurring inside the fire, the extra damage they couldn't guess at and the added mass of the plane or collapses caused by the impacts, their model actually showed less pulling in of the exterior columns than the video and photos shows actually occurred. Thus in the collapse simulation they set the inputs for the collapse to match what is seen in the actual RL photos and videos, not what their model said.
As to how they determined where the fire proofing was removed…
1) All SFRM and gypsum board insulation considered stripped or dislodged in regions where impact simulation indicated a debris field that could damage or destroy adjacent furniture and wall partitions
2) All gypsum board insulation considered stripped away from structural members where impact simulation predicted the structural member in question had suffered heavy damage
This would seem fair enough. In fact it appears from comparing NIST's results based on their testing and models and the images and the results obtained from video taken at the time of the fires on 9/11, their estimates of where and how much fireproofing was damaged has been vastly under-estimated, in fact NIST likely erred on the side of caution using far less fireproofing damage rather than stripping far more then actually was damaged.
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