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Ravenmoon
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DeFecToR
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 Posted: Sun Apr 29, 2007 6:34 pm Post subject: |
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Hate to sound like a critic here but that comparison that is often drawn to the Madrid building should really be avoided.
As can be seen in the above image much of the building did in fact collapse. That central column that can be seen still standing is made from concrete, not steel. None of which discounts the extraordinarily bizarre collapse of WTC 7, just that a structural engineer would take issue with the above comparison.
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Ravenmoon
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| Posted: Sun Apr 29, 2007 9:23 pm Post subject: |
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Blame prisonplanet for the comparison 
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Bongo
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| Posted: Sun Apr 29, 2007 10:38 pm Post subject: |
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Well, from someone who has done Structural Engineering and specialises in heat transfer and fluid mechanics, the Madrid building burned for 20 odd hours... and indeed the entire building was engulfed.
What happened in this fire was that the steel expanded (as steel expands under even small levels of heat as seen in the below photo from sunlight only)...
...and as the steel beams expanded, they pushed columns out causing partial collapse of portions of the building. This type of fire damage is typical in the biggest and longest burning fires, as the steel requires a constant and long duration of heat for it to start to expand. WTC7 in comparison burned for a few hours (I believe about 6 or there abouts) and the fires were not large enough (ie. they did not engulf the entire building) to cause the type of partial collapse as experienced in Madrid through expansion of steel.
In summary, the statement is true that steel will not melt in hydrocarbon fuelled fires (which is why melted steel in the basements remains a serious conundrum), although it will expand if the temperature is sufficient to overcome the specific heat capacity of the mass of steel to a point which the co-efficient of expansion of the steel becomes enough to cause significant structural damage.
Hence, there are many lessons from Madrid where comparisons can be made to WTC7, if indeed fire (ie NIST) is the assumed hypothesis for collapse.
Reference... 5.1.1 of the following document...
http://www.istructe.org/publications/files/Fire-Sample_pages.pdf |
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DeFecToR
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| Posted: Mon Apr 30, 2007 2:54 am Post subject: |
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| Bongo wrote: | Well, from someone who has done Structural Engineering and specialises in heat transfer and fluid mechanics, the Madrid building burned for 20 odd hours... and indeed the entire building was engulfed.
What happened in this fire was that the steel expanded (as steel expands under even small levels of heat as seen in the below photo from sunlight only)...
...and as the steel beams expanded, they pushed columns out causing partial collapse of portions of the building. This type of fire damage is typical in the biggest and longest burning fires, as the steel requires a constant and long duration of heat for it to start to expand. WTC7 in comparison burned for a few hours (I believe about 6 or there abouts) and the fires were not large enough (ie. they did not engulf the entire building) to cause the type of partial collapse as experienced in Madrid through expansion of steel.
In summary, the statement is true that steel will not melt in hydrocarbon fuelled fires (which is why melted steel in the basements remains a serious conundrum), although it will expand if the temperature is sufficient to overcome the specific heat capacity of the mass of steel to a point which the co-efficient of expansion of the steel becomes enough to cause significant structural damage.
Hence, there are many lessons from Madrid where comparisons can be made to WTC7, if indeed fire (ie NIST) is the assumed hypothesis for collapse.
Reference... 5.1.1 of the following document...
http://www.istructe.org/publications/files/Fire-Sample_pages.pdf |
Agreed. Perhaps i should have phrased myself a little better. Comparisons can indeed be made between these two events but the basic assertion that WTC 7 should not have collapsed because the Madrid building didn't is not accurate. Steel buildings can and have collapsed as a result of fire. Picking out a concrete supported building that did not collapse from fire and using this as an example of why a steel building should not have collapsed is akin to saying a house could withstand a missile impact because a bomb shelter can.
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Last edited by DeFecToR on Mon Apr 30, 2007 2:58 am; edited 1 time in total |
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DeFecToR
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| Posted: Mon Apr 30, 2007 2:55 am Post subject: |
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| Bongo wrote: | Well, from someone who has done Structural Engineering and specialises in heat transfer and fluid mechanics, the Madrid building burned for 20 odd hours... and indeed the entire building was engulfed.
What happened in this fire was that the steel expanded (as steel expands under even small levels of heat as seen in the below photo from sunlight only)...
...and as the steel beams expanded, they pushed columns out causing partial collapse of portions of the building. This type of fire damage is typical in the biggest and longest burning fires, as the steel requires a constant and long duration of heat for it to start to expand. WTC7 in comparison burned for a few hours (I believe about 6 or there abouts) and the fires were not large enough (ie. they did not engulf the entire building) to cause the type of partial collapse as experienced in Madrid through expansion of steel.
In summary, the statement is true that steel will not melt in hydrocarbon fuelled fires (which is why melted steel in the basements remains a serious conundrum), although it will expand if the temperature is sufficient to overcome the specific heat capacity of the mass of steel to a point which the co-efficient of expansion of the steel becomes enough to cause significant structural damage.
Hence, there are many lessons from Madrid where comparisons can be made to WTC7, if indeed fire (ie NIST) is the assumed hypothesis for collapse.
Reference... 5.1.1 of the following document...
http://www.istructe.org/publications/files/Fire-Sample_pages.pdf |
Agreed. Perhaps i should have phrased myself a little better. Comparisons can indeed be made between these two events but the basic assertion that WTC 7 should not have collapsed because the Madrid building didn't is not accurate. Steel buildings can and have collapsed as a result of fire. Picking out a concrete supported building that did not collapse from fire and using this as an example of why a steel building should not have collapsed is akin to saying a house could withstand a missile impact because a bomb shelter can.
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scubadiver
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| Posted: Mon Apr 30, 2007 7:08 am Post subject: |
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I had intended to use those two pictures for my booklet. Does this mean I should not?
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DeFecToR
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| Posted: Mon Apr 30, 2007 12:52 pm Post subject: |
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| scubadiver wrote: | I had intended to use those two pictures for my booklet. Does this mean I should not?
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Fraid' so Scuba. Its unfortunately another bad fact that 'our side' continues to put out.
I may be hated for saying this but if i were you and i was putting out a booklet of some kind I'd draw it up with all the info i wished to include then I'd run it by the critic sites to see what they have to say on each point. That way you'll have a far better product. After all, its somewhere between our points of view and theirs that something approaching truth lies.
Not a popular view amongst truthers i know. Just my two cents.
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