MicahJava
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If the entire length of column 20 could be removed like that, I may be wrong about the gash and it could have really existed.
I found the missing Jolt.
- Thread starter Crazy Chainsaw
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If the entire length of column 20 could be removed like that, I may be wrong about the gash and it could have really existed.
You're missing an important detail.
They don't claim it fell on a pristine floor.
They claim it fell on floors weakened by previous fires.
After 4.0 h of heating, the floor framing and slabs at Floors 8 to 14 were weakened by fires [...]
NCSTAR 1-9 Vol 2, p.531
The entire length of column 20 was not removed.
In the lower floors, the gash was not so wide as in the upper floors.
See NCSTAR 1-9 Vol 1, Section 5.5.2, pp. 130 to 187. Figure 5-83 in particular (in page 173) gives NIST's damage location estimation in the south face.
It seems that the gash only covered the space between two columns, except at the top where it removed a column section.
Tony Szamboti
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NIST says girder A2001 was heated to 500 degrees C and column 79 to 300 degrees C at floor 12, so the connection would probably be at about 400 degrees C. Per the AISC structural steel retains 75% of its yield strength at 500 degrees C, and 85% at 400 degrees C. I'll be conservative and say the entire connection was at the higher temperature.
To shear the seat of the floor 12 girder at column 79 required 632,000 lbs. at room temperature. Derated to 75% would require 474,000 lbs.
The falling 46,000 lb. beam and girder assembly shown in the Nordenson report cannot generate more than a 215,000 lb. amplified impact load when it is at its stiffest at room temperature with K = 6,633 lbs./inch. At higher temperature its modulus of elasticity goes down and it would deflect more and deliver even less of a shock load.
There is simply no way to break the floor below with a falling beam and girder assembly from one floor above. The eight floor cascade could not have happened. It is pure fiction. There is a reason the WTC 7 report does not provide a supporting analysis for this.
I would actually prefer not to have to say this but the science and math is saying what they are saying can't happen.
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Axxman300
Philosopher
You and other Troofers throw around the phrase "office fire" as if it is like a camp fire, or a fireplace fire. It is one of the many reasons you've failed.
First, it wasn't "an office fire" but hundreds of office fires which spread throughout the entire building, and burned out of control, unfought for almost eight hours. The acreage alone would technically classify it as a wildfire, and it took place in a confined area. Plus, you've ignored the damage caused by WTC1, which means you're basing calculations based on an intact structure and not a fatally damaged one.
The Bay Bridge on-ramp was outside, plenty of ventilation, and gasoline - not JP fueled:
The fire weakened the steel, and the concrete. The impact in this case occurred at 3:41 AM, and the collapse at 4:02 AM.
*source:
http://www.sfgate.com/bayarea/article/Tanker-fire-destroys-part-of-MacArthur-Maze-2-2575285.php
It wasn't jet fuel, it wasn't a plane crash, and yet an earthquake-hardened structure was felled by fire weakening steel.
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Crazy Chainsaw
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100,000 Foot pounds per inch is 2600 pounds dropped 12 ft.
46000 pound could generate, over 813846.15383 Foot pounds per inch, in a Twelve foot fall.
Tony Szamboti
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I didn't say fire could not weaken steel. I have said there usually isn't enough fuel and energy in office fires to heat large pieces of steel to the point where they weaken enough to fail and that is why steel framed high-rise buildings never collapsed from fire.
In this case it was a gasoline tanker truck burning right under the connections of the beams under the highway section. There was no shortage of fuel. The connections failed and the upper section dropped.
Anyway, you are actually proving the germane point I am making. That is that the upper highway section did not break through the lower section when it fell on it.
You seem to think this somehow proves your point. I would argue that you are using an extreme case which has rarely happened and it was an enormous amount of concentrated fuel. Only one section fell and did no more damage. To then somehow try to use this one off very limited collapse to provide support for the complete propagation of collapses in three enormous buildings on the same day has no basis and is somewhat inane.
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Axxman300
Philosopher
There are a number of fallacies right here, being that most office fires are brought under control by sprinkler systems before the FD shows up, and then most office fires are prosecuted by the FD upon arrival. WTC7 was not. So we don't know what happens when you allow a building to burn unmolested for 8 hours. Now we do.
The next problem is that there have been 3 high rise office buildings of similar design to have collapsed from extreme fire and impact damage: WTC1, WTC2, and WTC7.
Weird how the connections failed in 20 minutes, almost like fire weakened the connections.
No, in the case of the Bay Bridge the fire was localized. The lower section was damaged and had to be replaced as well. The fires in WTC7 were on multiple floors.
More to the point, the 7 collapse happened over a 20 minute period, and I suspect what you see here was happening in parts of the building as well, adding to the stress of the already damaged structure.
No, it has happened at least three times. Nine Mile Bridge in MI, and we had an overpass in Central CA fail too after a tanker truck ignited under it.
No, controlled demolition is inane.
And in the case of 9-11, 2001, it's just ridiculous.
So, let me get this straight ...
Planes flew into the sides of those two towers ...
Huge amounts of damage was done to the external columns, the internal columns & the floor systems on the impact floors ...
Massive fire broke out ...
The fires burned for just shy of 1 & 2 hours in the 2 towers ...
The towers collapsed ...
And you assert, with the "authority" of your mechanical engineering degree, that "the collapse was NOT caused by the plane impacts & subsequent fires, but due to a completely different cause.
Is that about right?
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This is my understanding of it too. A composite photo of the whole gash is included below, but the point is the columns guided the progress of whatever caused the damage, whereas simply clipping off facade panels in such a straight line is highly improbable.
Attachments
Tony Szamboti
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Most high-rises did not even have sprinkler systems prior to the 1990s. There was a major high-rise fire in the Philadelphia area where I live in 1991 (the 38 story Meridian Plaza building) that burned for 19 hours. The building was having sprinklers installed but the system was not yet installed or not activated on the 8 upper stories where the fire burned. No collapse.
The North Tower of the WTC had a serious fire on the 11th floor and parts of six other floors in 1975 which burned for over three hours. The building did not have sprinklers at the time. No collapse.
In fact, none of the fires in steel framed high-rises prior to the installation of sprinkler systems ever caused a total collapse. This only ever happened on Sept. 11, 2001 and it happened to three buildings on the same day, that were located in the same area, in the same city, and owned by the same person. Wow, what a coincidence! Although these would have purportedly been the first buildings to completely collapse due to fire, none of the steel was salvaged for an investigation from WTC 7 and only 0.25 to 0.50% from the twin towers, because the mayor's office felt it was prudent to recycle the steel instead of saving it for an investigation. Why would anyone be suspicious?
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^ False comparison.
I don't think those buildings had the drywall and SFRM protecting any of their steel knackered and exposed to fires by high-speed impact of aircraft parts. Nor did they get a massive dose of accelerant in the form of jet fuel.
I don't think those buildings had the drywall and SFRM protecting any of their steel knackered and exposed to fires by high-speed impact of aircraft parts. Nor did they get a massive dose of accelerant in the form of jet fuel.
Dave Rogers
Bandaged ice that stampedes inexpensively through
You're thinking along the right lines - it's intuitively clear that anything that straight and vertical must be very closely related to the column structure of the perimeter - but there doesn't have to be a column missing. There's a well-known picture of the collapse of WTC1 that shows a trail of dust from a big piece of debris that fell outwards and hit WTC7 at the top of the south façade. If that piece of debris struck somewhere between two columns, it could have taken out the cross-member between them, and with enough weight and speed it could then have fallen on to the next cross-member down, and the next, and so on down the façade. The result would be a vertical gash with well-defined edges and the floors visible behind, which is exactly what we see in the pictures of WTC7. The effect of this on the stability of the building would be quite drastic. The tube-in-tube design of WTC1, 2 and 7 relied on the stiffness of the perimeter column assembly to resist sideways forces on the building. The damage to WTC7 appears to have cut the south façade in half, meaning that about half the resistance to bending and twisting of the structure in that direction was gone. It clearly didn't contribute to the actual collapse we saw - the details of the penthouse collapses make it clear that the core collapse came first - but it must have weakened the building, and opened up large areas to admit enough air to allow the fires to burn hotter and faster.
Dave
Are you claiming that's the only thing that imposed dynamic loads on floor 12?
That there wasn't anything they were supporting, not even floor slabs? Are you joining Yankee451 on his "empty building" nonsense?
Yeah. I pointed her to the relevant section of the NIST report for a reason. Figure 5-53 in particular shows clearly that the damage extended to the inside.
Tony Szamboti
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Read Nordenson's Volume 2 Appendix B and you will see the 46,000 lbs. is what the falling steel and slab would apply statically at its column 79 corner on the slab below. Of course, there would have been an impact and that load is found using potential energy, stiffness, and deflection. It would have been about 215,000 lbs. at room temperature. That is an amplification of about 5 to 1.
You can find the Nordenson report at the bottom of this linked post on Metabunk.org here https://www.metabunk.org/aegis-insurance-v-7-world-trade-company-expert-reports.t7112/
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No I can't. Metabunk blocks Tor users.
Tony Szamboti
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I could e-mail the pdf to you if you private message me with your e-mail address.
Crazy Chainsaw
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Why don't you just link the PDF, directly?
You don't have to link it though metabunk.