01-10-2012, 11:16 AM
(This post was last modified: 01-10-2012, 04:03 PM by Jeffrey Orling.)
Phil,
The release of drawings from WTC 7 was very long in coming and very confusing to say the least. Take a look at what FEMA published... note the structure from 1-7 and how few columns there were compared to above (40 something compared with 81). Note how they do not show the structure clearly on floors 1-7 and only snippets. There appears to be only 40+ columns below floor 8 and 81 above. Note some of the exceedingly long spans in the flrs 1-8 to accommodate the ramp and Con Ed. FEMA only refer to trusses 1, 2 and 3 but most of the structure below 8 were trusses and cantilevers. Note how the north columns opposite the core had no support going through the con ed sub station... they rested on the ends of the cantilevers.
You will not find a hi rise in the world of that size or close with such a bizarre structure.
It appears that many of the columns above flr 8 had no DIRECT load path to bedrock. This meant that those columns are supported somewhere on a beam span or truss span. This is a very bizarrre and essentially precarious means of moving the massive loads from above to bedrock. So when someone claims 8 stories of (81) columns had to be destroyed for FF... it should be noted that there were only 40 something below 8 and many above were not in direct line with the columns from flr 1 - 8.
My explanation is a theory... a hypothesis driven by understanding the structure and noting the actual movement of the building and correlating the two. I can't prove that fuel fires caused the structural failures below 8 and or that they were started by electrical equipment explosions, but it is worthing of serious consideration. The fact that the collapse took 8 hrs could be because there was a long steady process of weakening from heating... the steel was quite thick and took a long time to heat up and weaken.
But once a structure loses some of its members there IS a load redistribution to remaining members which consumes some (or all) of their reserve strength. If the redistribution consumes ALL of the reserve strength of a member it will fail and its load and the load which was redistributed to it is then redistributed to other members and so on. This is how a progressive structural failure moves/cascades through the frame until there is not enough strength to support the loads above and there is a rapid onset almost instantenous collpase... when the FOS drops below 1.
The early movements observed are telltale signs that the structure is under stress and loads are being redistributed as columns fail (dropping of the East and West penthouses). The swaying of the entire tower is clearly a sign that the loads are being moved to new members.
Again these failures COULD HAVE BEEN from placed devices in the locations noted above. Can't rule this out. But perhaps it was from a heat from diesel, oil and gas flames. Yes we can't see those flames. But we don't have pictures that show there was no fire or there was fire.
The release of drawings from WTC 7 was very long in coming and very confusing to say the least. Take a look at what FEMA published... note the structure from 1-7 and how few columns there were compared to above (40 something compared with 81). Note how they do not show the structure clearly on floors 1-7 and only snippets. There appears to be only 40+ columns below floor 8 and 81 above. Note some of the exceedingly long spans in the flrs 1-8 to accommodate the ramp and Con Ed. FEMA only refer to trusses 1, 2 and 3 but most of the structure below 8 were trusses and cantilevers. Note how the north columns opposite the core had no support going through the con ed sub station... they rested on the ends of the cantilevers.
You will not find a hi rise in the world of that size or close with such a bizarre structure.
It appears that many of the columns above flr 8 had no DIRECT load path to bedrock. This meant that those columns are supported somewhere on a beam span or truss span. This is a very bizarrre and essentially precarious means of moving the massive loads from above to bedrock. So when someone claims 8 stories of (81) columns had to be destroyed for FF... it should be noted that there were only 40 something below 8 and many above were not in direct line with the columns from flr 1 - 8.
My explanation is a theory... a hypothesis driven by understanding the structure and noting the actual movement of the building and correlating the two. I can't prove that fuel fires caused the structural failures below 8 and or that they were started by electrical equipment explosions, but it is worthing of serious consideration. The fact that the collapse took 8 hrs could be because there was a long steady process of weakening from heating... the steel was quite thick and took a long time to heat up and weaken.
But once a structure loses some of its members there IS a load redistribution to remaining members which consumes some (or all) of their reserve strength. If the redistribution consumes ALL of the reserve strength of a member it will fail and its load and the load which was redistributed to it is then redistributed to other members and so on. This is how a progressive structural failure moves/cascades through the frame until there is not enough strength to support the loads above and there is a rapid onset almost instantenous collpase... when the FOS drops below 1.
The early movements observed are telltale signs that the structure is under stress and loads are being redistributed as columns fail (dropping of the East and West penthouses). The swaying of the entire tower is clearly a sign that the loads are being moved to new members.
Again these failures COULD HAVE BEEN from placed devices in the locations noted above. Can't rule this out. But perhaps it was from a heat from diesel, oil and gas flames. Yes we can't see those flames. But we don't have pictures that show there was no fire or there was fire.