Something I was wondering about, so I thought I'd ask those with expertise in structual engineering (like Mr. Wong).
Basically, what would happen if a fully-fueled midsized airliner (like an A330 or a B767) was crashed into the CN Tower in a WTC-style terrorist attack? Obviously it would depend a great deal on where the airliner hit, so for this scenario let's assume a direct hit on one of the 3 main concrete columns about 1/3 of the way up. I remember reading somewhere that the tower was designed to withstand the impact of a large plane, but then again, so was the WTC.
If this scenario is enough to bring down the tower, how would it collapse? Would it "implode" WTC-style, or would it crash over on it's side? If the tower is able to survive this scenario, would a larger aircraft (like a 747) be enough to bring it down?
A disclaimer just to be absolutely sure: No I am not hatching some evil scheme here, I am simply curious
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The WTC was brought down by fire and the destruction of load-bearing exterior columns. There's nothing on the CN tower to burn and meters-thick reinforced concrete is much tougher than ordinary steel columns. My guess is that the tower would be shaken but not seriously damaged. Sucks for the people on the ground getting sprayed with burning jet fuel, though.
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Assuming their was enough force to fatally damage the main column it would likely topple over side ways due to its shape and form and would end up smashing on top of whatever buildings are underneath it. The worst would be if it toppled in the direction of the large banking towers next to it causing one or two of the main bank skyscrapers to be destroyed as well.
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If the tower is hit 1/3 of the way up, then I can't see how the upper 2/3rds could avoid being incinerated. That might not bring down the tower, but intense fires will severely damage reinforced concrete, and in any case with most of the tower burned out it would have to be demolished.
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I think that the CN Tower is one (or a small number) of very large continuous concrete sections, because I seem to remember on one of my visits there that the tour guide said they poured the concrete continuously around the clock during construction.
I expect that, provided the nose of the airliner and not a wing hit the main tower body, that it would break and topple. I don't think that there is too much that would be flammable or that could weaken so I'm not sure if fire would be a main factor in its collapse. However, the CN Tower is much thinner than the Twin Towers, so I think that the impact alone stands a better chance of bringing it down.
The ratio of structural support to interior space is much greater for the CN Tower than it was for the WTC. The CN Tower has no real interior space to speak of; it's just elevator shafts and stairwells and such. And one of the things that brought down the WTC was all of the fuel that poured into the interior spaces and burned. The CN Tower's stairwells and elevator shafts are open to the outside except for the enclosing windows, so you're not going to get that much sustained fire going in there.
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"you guys are fascinated with the use of those "rules of logic" to the extent that you don't really want to discussus anything."- GC
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Also, if you look at the CN Tower, any given face of it (up to the 'Sky Pod' or whatever it is called) is outward pointing Concreate. Only a very small (comparative) horitzonal surface area is not multi-foot think reinforced concreate.
An airliner would hit it, smash the windows over the stairwell, the cockpit would wedge some of the way in, and then the wings with all the fuel would hit the concreate and stop.
Really, unless the plane was flying at a perfect 90 degree angle to the ground (thereby lining up perfectly with the glass), before the engines or fuel would get into the tower, it would hit concreate and stop.
No more effect then a 2x4 being shot by a nail gun. Sure, the plane is going to do some damage, but probably nothing to significant.
Also, I can't imagine that the owners of the CN Tower, with it beside Skydome, a major tourist attraction, and near one of the busiest intersections in toronto haven't done some upgrading to it's fire containment systems (i.e more water in the sprinkers and more sprinkers) in case this were to happen.
I agree however, it would majorly SUCK to be on the ground or a bulding within several hundred feet of the Tower if someone tried it. Flaming Jet fuel is not fun to be burned with or inhale the fumes of at least in large quantities
Solauren wrote:
An airliner would hit it, smash the windows over the stairwell, the cockpit would wedge some of the way in, and then the wings with all the fuel would hit the concreate and stop.
I think not. The walls of the Pentagon where each made of two foot thick concert, with the outer wall having a web of steel I beams welded behind for extra strength and a curtain of Kevlar to catch fragments. The aircraft managed to pierce something like six of those walls before the last debries stopped.
"This cult of special forces is as sensible as to form a Royal Corps of Tree Climbers and say that no soldier who does not wear its green hat with a bunch of oak leaves stuck in it should be expected to climb a tree"
— Field Marshal William Slim 1956
Solauren wrote:An airliner would hit it, smash the windows over the stairwell, the cockpit would wedge some of the way in, and then the wings with all the fuel would hit the concreate and stop.
I think not. The walls of the Pentagon where each made of two foot thick concert, with the outer wall having a web of steel I beams welded behind for extra strength and a curtain of Kevlar to catch fragments. The aircraft managed to pierce something like six of those walls before the last debries stopped.
The interior walls are just as thick as the exterior walls? I've never heard that before. I also heard the exterior walls were limestone, and the interior steel reinforcing beams were added recently in an attempt to reinforce them because they weren't very strong. I'm not sure how well that would compare to the pretensioned steel-reinforced concrete used in the CN Tower; that stuff would be stronger but I'm not sure how much stronger.
"It's not evil for God to do it. Or for someone to do it at God's command."- Jonathan Boyd on baby-killing
"you guys are fascinated with the use of those "rules of logic" to the extent that you don't really want to discussus anything."- GC
"I do not believe Russian Roulette is a stupid act" - Embracer of Darkness
"Viagra commercials appear to save lives" - tharkûn on US health care.
Darth Wong wrote:The interior walls are just as thick as the exterior walls? I've never heard that before. I also heard the exterior walls were limestone, and the interior steel reinforcing beams were added recently in an attempt to reinforce them because they weren't very strong. I'm not sure how well that would compare to the pretensioned steel-reinforced concrete used in the CN Tower; that stuff would be stronger but I'm not sure how much stronger.
I've been trying to find out some information about the construction of the Pentagon, and aside from too many sites with conspiracy theories about what exactly hit the Pentagon. This is from ArchitectureWeek (the most reliable-sounding site I've found so far):
Ironically, the fortress-like appearance provided by the exterior Indiana limestone is misleading. The limestone is not structural but a veneer supported by steel hangers. As the facade is repaired in the near future, matching replacement stone will come from the original quarry in deference to the building's historic status.
Unfortuantely there is no mention I've yet seen of the actual thickness of the inner and outer walls.
Darth Wong wrote:I also heard the exterior walls were limestone, and the interior steel reinforcing beams were added recently in an attempt to reinforce them because they weren't very strong.
IIRC, the limestone is not structual, but merely a decorative facade attached to the Pentagon's actual walls. As originally built in the '40s, the structual walls themselves are brick infill supported by reinforced concrete beams and columns between each of the concrete floors, though following the Oklahoma City bombing, work was begun to shore up the walls further by installing floor-to-ceiling steel I-beam structures surrounding every window frame and adding a kevlar liner to the walls, the purpose being to increase their blast resistance.
The M2HB: The Greatest Machinegun Ever Made.
HAB: Crew-Served Weapons Specialist
"Making fun of born-again Christians is like hunting dairy cows with a high powered rifle and scope." --P.J. O'Rourke
"A man who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself." --J.S. Mill
Darth Wong wrote:I also heard the exterior walls were limestone, and the interior steel reinforcing beams were added recently in an attempt to reinforce them because they weren't very strong.
IIRC, the limestone is not structual, but merely a decorative facade attached to the Pentagon's actual walls. As originally built in the '40s, the structual walls themselves are brick infill supported by reinforced concrete beams and columns between each of the concrete floors, though following the Oklahoma City bombing, work was begun to shore up the walls further by installing floor-to-ceiling steel I-beam structures surrounding every window frame and adding a kevlar liner to the walls, the purpose being to increase their blast resistance.
That doesn't sound like it would match up to steel-reinforced concrete of the same thickness. But I don't actually know how thick the CN Tower walls are; it's not solid, contrary to popular belief. If it were solid, its own weight would make it impossible to build the tower that tall. They tried to use an optimal cross-section to maximize height while retaining strength. However, the walls are the structural support for the tower, so they should be pretty thick and strong.
"It's not evil for God to do it. Or for someone to do it at God's command."- Jonathan Boyd on baby-killing
"you guys are fascinated with the use of those "rules of logic" to the extent that you don't really want to discussus anything."- GC
"I do not believe Russian Roulette is a stupid act" - Embracer of Darkness
"Viagra commercials appear to save lives" - tharkûn on US health care.
This site has a breakdown of how much steel & concrete is in the tower as well as how much it weighs. If a site can be found giving the dimensions of the tower, the amount of empty space inside it and the approximate wall thickness could be roughly estimated.
aerius: I'll vote for you if you sleep with me. Lusankya: Deal!
Say, do you want it to be a threesome with your wife? Or a foursome with your wife and sister-in-law? I'm up for either.
aerius wrote:This site has a breakdown of how much steel & concrete is in the tower as well as how much it weighs. If a site can be found giving the dimensions of the tower, the amount of empty space inside it and the approximate wall thickness could be roughly estimated.
This site is also worth looking at: It has a wealth of structural diagrams of various parts of the tower, especially the main shaft.
The M2HB: The Greatest Machinegun Ever Made.
HAB: Crew-Served Weapons Specialist
"Making fun of born-again Christians is like hunting dairy cows with a high powered rifle and scope." --P.J. O'Rourke
"A man who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself." --J.S. Mill
aerius wrote:This site has a breakdown of how much steel & concrete is in the tower as well as how much it weighs. If a site can be found giving the dimensions of the tower, the amount of empty space inside it and the approximate wall thickness could be roughly estimated.
This site is also worth looking at: It has a wealth of structural diagrams of various parts of the tower, especially the main shaft.
There are no useful dimensions, however. And the diagrams may not even be strictly to scale, since they're not real engineering drawings.
"It's not evil for God to do it. Or for someone to do it at God's command."- Jonathan Boyd on baby-killing
"you guys are fascinated with the use of those "rules of logic" to the extent that you don't really want to discussus anything."- GC
"I do not believe Russian Roulette is a stupid act" - Embracer of Darkness
"Viagra commercials appear to save lives" - tharkûn on US health care.
