happycamper Posted March 9, 2017 Share Posted March 9, 2017 All right guys, here's the big one if this bracket started in 2005. 9/11 Was an Inside Job, a Kind of Reichstag Fire What is this rabbit hole about? The main gist of it is that the 9/11 terrorist attack wasn't caused by Al Qaeda at all - that it was caused by a secret government or members of the US government. Wait, what? Don't give me that shit. You've heard of this one. Okay. Still, why would people believe that? There are several things. First off is the video "Loose Change" : It's long. Really long. Still, it convinced a ton of people. Next there was the fact that the timing of the attack seemed mighty convenient to some people. Bush's approval ratings were flagging, the office that the pentagon plane crashed in to just happened to be auditing 2 trillion in missing funds. More telling is the fact that there was a Patriot Act up and ready to be proposed immediately. This is sketchy, as if the administration and congress knew they'd have an excuse to pass it. There was more pieces of evidence - like the fact that the concrete of the buildings pulverized, like that jet fuel does not burn hot enough to melt steel, like that the towers fell at the speed of gravity instead of slowing down as people imagined they should. The collapse of world trade center building 7 is also cited as proof of this. I have a lot- a lot - of debunking I can do with this, but I'll let you guys go down this rabbit hole yourselves and ask questions before I start going point by point (if that becomes necessary). Have fun digging! Quote Remember that every argument you have with someone on MWCboard is actually the continuation of a different argument they had with someone else also on MWCboard. Link to comment Share on other sites More sharing options...
youngredbullfan Posted March 9, 2017 Share Posted March 9, 2017 Traces of thermite were found in the rubble. Thermite that is found in explosives. Mind=blown. Quote On 12/1/2016 at 12:26 PM, WyomingCoog said: I own a vehicle likely worth more than everything you own combined and just flew first class (including a ticket for a 2 1/2 year old), round trip to Las Vegas and I'm not 35 yet. When you accomplish something outside of finishing a book, let me know. When's the last time you saw a 2 year old fly first class in their own seat? Don't tell me about elite. 28 minutes ago, NorCalCoug said: I’d happily compare IQ’s with you any day of the week. Link to comment Share on other sites More sharing options...
bigd Posted March 9, 2017 Share Posted March 9, 2017 From Trump himself LOL: Quote Link to comment Share on other sites More sharing options...
Jimbo_Poke Posted March 10, 2017 Share Posted March 10, 2017 I don't want to steal your thunder in the debunking portion, but the whole jet fuel doesn't burn hot enough to melt steel is one of those things that really blows a gasket in my head. Doesn't need to, burns hot enough to soften and reduce the yield strength of the steel which in turn greatly reduces the steel's resistance to buckling... 8 Quote Link to comment Share on other sites More sharing options...
DestinFlPackfan Posted March 10, 2017 Share Posted March 10, 2017 3 hours ago, Jimbo_Poke said: I don't want to steal your thunder in the debunking portion, but the whole jet fuel doesn't burn hot enough to melt steel is one of those things that really blows a gasket in my head. Doesn't need to, burns hot enough to soften and reduce the yield strength of the steel which in turn greatly reduces the steel's resistance to buckling... Couple the flammability of jet fuel with all the other combustibles in a building- makes for one hell of a hot fire. 1 Quote Link to comment Share on other sites More sharing options...
PTR Posted March 10, 2017 Share Posted March 10, 2017 3 hours ago, Jimbo_Poke said: I don't want to steal your thunder in the debunking portion, but the whole jet fuel doesn't burn hot enough to melt steel is one of those things that really blows a gasket in my head. Doesn't need to, burns hot enough to soften and reduce the yield strength of the steel which in turn greatly reduces the steel's resistance to buckling... and the design of WTC was particularly susceptible to collapse under those conditions. Quote Link to comment Share on other sites More sharing options...
toonkee Posted March 10, 2017 Share Posted March 10, 2017 3 hours ago, Jimbo_Poke said: I don't want to steal your thunder in the debunking portion, but the whole jet fuel doesn't burn hot enough to melt steel is one of those things that really blows a gasket in my head. Doesn't need to, burns hot enough to soften and reduce the yield strength of the steel which in turn greatly reduces the steel's resistance to buckling... Also, there were some sort of connector pieces that joined the horizontal beams to the vertical ones. All that needed to happen was for those to fail. Quote Link to comment Share on other sites More sharing options...
youngredbullfan Posted March 10, 2017 Share Posted March 10, 2017 7 hours ago, Jimbo_Poke said: I don't want to steal your thunder in the debunking portion, but the whole jet fuel doesn't burn hot enough to melt steel is one of those things that really blows a gasket in my head. Doesn't need to, burns hot enough to soften and reduce the yield strength of the steel which in turn greatly reduces the steel's resistance to buckling... Engineering is a conspiracy 1 Quote On 12/1/2016 at 12:26 PM, WyomingCoog said: I own a vehicle likely worth more than everything you own combined and just flew first class (including a ticket for a 2 1/2 year old), round trip to Las Vegas and I'm not 35 yet. When you accomplish something outside of finishing a book, let me know. When's the last time you saw a 2 year old fly first class in their own seat? Don't tell me about elite. 28 minutes ago, NorCalCoug said: I’d happily compare IQ’s with you any day of the week. Link to comment Share on other sites More sharing options...
crixus Posted March 10, 2017 Share Posted March 10, 2017 3 minutes ago, youngrebelfan40 said: Engineering is a conspiracy Congratulations, you're officially insane! 1 Quote Link to comment Share on other sites More sharing options...
youngredbullfan Posted March 10, 2017 Share Posted March 10, 2017 Just now, crixus said: Congratulations, you're officially insane! And you're a useful idiot for the shadow government. Human cattle being led to the slaughter. Quote On 12/1/2016 at 12:26 PM, WyomingCoog said: I own a vehicle likely worth more than everything you own combined and just flew first class (including a ticket for a 2 1/2 year old), round trip to Las Vegas and I'm not 35 yet. When you accomplish something outside of finishing a book, let me know. When's the last time you saw a 2 year old fly first class in their own seat? Don't tell me about elite. 28 minutes ago, NorCalCoug said: I’d happily compare IQ’s with you any day of the week. Link to comment Share on other sites More sharing options...
happycamper Posted March 10, 2017 Author Share Posted March 10, 2017 15 hours ago, Jimbo_Poke said: I don't want to steal your thunder in the debunking portion, but the whole jet fuel doesn't burn hot enough to melt steel is one of those things that really blows a gasket in my head. Doesn't need to, burns hot enough to soften and reduce the yield strength of the steel which in turn greatly reduces the steel's resistance to buckling... Oh sure the yield strength went down. But who cares? Euler buckling is governed by modulus of elasticity and section properties, not yield strength!!!!! Quote Remember that every argument you have with someone on MWCboard is actually the continuation of a different argument they had with someone else also on MWCboard. Link to comment Share on other sites More sharing options...
happycamper Posted March 10, 2017 Author Share Posted March 10, 2017 11 hours ago, toonkee said: Also, there were some sort of connector pieces that joined the horizontal beams to the vertical ones. All that needed to happen was for those to fail. From what I recall the WTC was a moment frame building. The "connector pieces" would have been stronger than the beams. 1 Quote Remember that every argument you have with someone on MWCboard is actually the continuation of a different argument they had with someone else also on MWCboard. Link to comment Share on other sites More sharing options...
Jimbo_Poke Posted March 10, 2017 Share Posted March 10, 2017 8 hours ago, youngrebelfan40 said: Engineering is a conspiracy Darn straight 25 minutes ago, happycamper said: Oh sure the yield strength went down. But who cares? Euler buckling is governed by modulus of elasticity and section properties, not yield strength!!!!! You dastardly foe, you going to make me go all theoretical on ya? Euler buckling based on modulus of elasticity and section properties is valid only as long as the loading remains in the elastic region. Dropping yield strength reduces the elastic-inelastic threshold thereby reducing the buckling stress. Edit- the whole KL/r<4.71(E/Fy)^1/2 check. 4 Quote Link to comment Share on other sites More sharing options...
Jimbo_Poke Posted March 10, 2017 Share Posted March 10, 2017 Also Euler buckling is assuming ideal column, we haven't even touched on eccentric loading of the column and subsequent P- Δ effects. 2 Quote Link to comment Share on other sites More sharing options...
happycamper Posted March 10, 2017 Author Share Posted March 10, 2017 3 minutes ago, Jimbo_Poke said: Darn straight You dastardly foe, you going to make me go all theoretical on ya? Euler buckling based on modulus of elasticity and section properties is valid only as long as the loading remains in the elastic region. Dropping yield strength reduces the elastic-inelastic threshold thereby reducing the buckling stress. Fcr check. The building had multiple brace points, had composite floors, and had very tightly spaced columns. The KL of the columns was short enough that dammit this is hurting my "argument" because it will make true compression and not Euler buckling control. Hmm. ooh, to "worst case scenario". At that time all design was done with ASD loading and the live loading was an unreduced 50 psf. Furthermore, the building was designed for about 40 psf of wind load which is equivalent to 145 mph if I'm remembering the last gulf coast area skid design correctly. If was a calm day, evidenced by the plume of smoke, and 50 psf is rather conservative. Therefore the actual stresses experienced by the columns were not just on the ~55% of yield that the maximum load combination would expect for design of that time but more like ~20%. 1 minute ago, Jimbo_Poke said: Also Euler buckling is assuming ideal column, we haven't even touched on eccentric loading of the column and subsequent P- Δ effects. The columns were braced exceptionally closely in both y and z directions due to the construction of the building with composite floors and other steel members. P-delta would be reduced because of the number of bracing points. Also it gets tough to argue that it's inelastic buckling that controlled and P-delta. Furthermore the building pancaked instead of toppled so P-delta seems to be out to me at least unless you have some reason why all columns would be initially rotating inward. Quote Remember that every argument you have with someone on MWCboard is actually the continuation of a different argument they had with someone else also on MWCboard. Link to comment Share on other sites More sharing options...
Jimbo_Poke Posted March 10, 2017 Share Posted March 10, 2017 1 minute ago, happycamper said: The building had multiple brace points, had composite floors, and had very tightly spaced columns. The KL of the columns was short enough that dammit this is hurting my "argument" because it will make true compression and not Euler buckling control. Hmm. ooh, to "worst case scenario". At that time all design was done with ASD loading and the live loading was an unreduced 50 psf. Furthermore, the building was designed for about 40 psf of wind load which is equivalent to 145 mph if I'm remembering the last gulf coast area skid design correctly. If was a calm day, evidenced by the plume of smoke, and 50 psf is rather conservative. Therefore the actual stresses experienced by the columns were not just on the ~55% of yield that the maximum load combination would expect for design of that time but more like ~20%. The columns were braced exceptionally closely in both y and z directions due to the construction of the building with composite floors and other steel members. P-delta would be reduced because of the number of bracing points. Also it gets tough to argue that it's inelastic buckling that controlled and P-delta. Furthermore the building pancaked instead of toppled so P-delta seems to be out to me at least unless you have some reason why all columns would be initially rotating inward. Nope. There are a couple things going on. First, you already have a compromised structure because of the damaged columns from the impact of the plane. Then consider yield strength of steel is reduced by anywhere from 50 to 80% at the temperature jet fuels burn. Reducing your fy by 50% makes it so you go from meeting a slenderness ratio of 113 vs 160 and not only is your slenderness limit increased, but your critical stress is reduced. I don't have the time now to do the calculation but that reduces your available column strength significantly. Given the reduction in you column strength of the frame system from the impact and subsequent fire and considering eccentricities, localized stresses, and other imperfections I would not be confident in that structure holding up the dead load of the building itself. Now the failure, that the towers collapsed near vertically is evidence of a progressive failure in the steel columns from dead load. Load follows stiffness. One column fails, the load is transferred to the adjacent columns that fail this proceeds (probably fairly rapidly) until all the the columns of a floor fail. Once the final columns fail that floor collapses and then it is game over. Reason for initially rotating inwards. What force is acting on the columns to rotate outward? The weight of the building is all in the interior. The only outward would be if the columns were loaded eccentrically outward. Regardless that rotation relative to the size of the building is fairly minor. So while even a 2-5% eccentricity matters greatly to the available strength in an individual column, as far as causing the column to rotate out during failure and topple, I don't see it with the floor framing and weight. It is going to come down near vertically. Quote Link to comment Share on other sites More sharing options...
happycamper Posted March 10, 2017 Author Share Posted March 10, 2017 Just now, Jimbo_Poke said: Nope. There are a couple things going on. First, you already have a compromised structure because of the damaged columns from the impact of the plane. Then consider yield strength of steel is reduced by anywhere from 50 to 80% at the temperature jet fuels burn. Reducing your fy by 50% makes it so you go from meeting a slenderness ratio of 113 vs 160 and not only is your slenderness limit increased, but your critical stress is reduced. I don't have the time now to do the calculation but that reduces your available column strength significantly. Given the reduction in you column strength of the frame system from the impact and subsequent fire and considering eccentricities, localized stresses, and other imperfections I would not be confident in that structure holding up the dead load of the building itself. Oh come on we both know you have a mathcad file that insta calcs column buckling. And the building had different strengths going up, from 100 ksi at the base to standard A36 at the top. How do you know what the grade was at the point of impact? For that matter, one plane "hit" lower than the other but they both collapsed in the same manner. You'd expect a different failure mode if the yield strength of the columns changed, no? Just now, Jimbo_Poke said: Now the failure, that the towers collapsed near vertically is evidence of a progressive failure in the steel columns from dead load. Load follows stiffness. One column fails, the load is transferred to the adjacent columns that fail this proceeds (probably fairly rapidly) until all the the columns of a floor fail. Once the final columns fail that floor collapses and then it is game over. That's where you'd expect to see P-delta, no? the columns nearest the plane impact would fail first, causing effectively the slab to have a pin connection on one side. That floor would rotate the columns of the other side down, causing a p-delta situation where the building topples towards where the line of weak columns failed! The top rotates towards the failed columns and fails as a macro bending situation (the while building bends). Just now, Jimbo_Poke said: Reason for initially rotating inwards. What force is acting on the columns to rotate outward? The weight of the building is all in the interior. The only outward would be if the columns were loaded eccentrically outward. Regardless that rotation relative to the size of the building is fairly minor. So while even a 2-5% eccentricity matters greatly to the available strength in an individual column, as far as causing the column to rotate out during failure and topple, I don't see it with the floor framing and weight. It is going to come down near vertically. See above, one side of columns would have been weaker, and if the columns of the impact site were damaged, the undamaged top ~20 stories will rotate enough that they'll case buckling failure in the columns above the damaged floor. furthermore, 2-5% eccentricity? Isn't L/500 the standard in AISC 13 at least? BTW it is REALLY hard to try to justify this with facts but it is a bit more fun. Quote Remember that every argument you have with someone on MWCboard is actually the continuation of a different argument they had with someone else also on MWCboard. Link to comment Share on other sites More sharing options...
Jimbo_Poke Posted March 10, 2017 Share Posted March 10, 2017 29 minutes ago, happycamper said: Oh come on we both know you have a mathcad file that insta calcs column buckling. Mathcad? I am a consultant in Buffalo, Wyoming we don't have money for mathcad! Quote And the building had different strengths going up, from 100 ksi at the base to standard A36 at the top. How do you know what the grade was at the point of impact? For that matter, one plane "hit" lower than the other but they both collapsed in the same manner. You'd expect a different failure mode if the yield strength of the columns changed, no? Yield Strength as a percentage of max yield strength vs Temperature for steel is fairly uniform. In other words 100ksi vs 50 ksi vs 36 ksi will have similar reductions in yield strength percentage wise. Also the difference in grade of different parts of the building likely reflect larger load demands for that portion of the building. Both buildings were subject to similar impact loads and subsequent fires. I would expect similar failure modes. Things may have been different had the planes impacted the corner of one of the buildings. Quote That's where you'd expect to see P-delta, no? the columns nearest the plane impact would fail first, causing effectively the slab to have a pin connection on one side. That floor would rotate the columns of the other side down, causing a p-delta situation where the building topples towards where the line of weak columns failed! The top rotates towards the failed columns and fails as a macro bending situation (the while building bends). See above, one side of columns would have been weaker, and if the columns of the impact site were damaged, the undamaged top ~20 stories will rotate enough that they'll case buckling failure in the columns above the damaged floor. This is a common perception on collapses. But from my experience with collapsed structures, it just doesn't work out that way most of the time. The floor framing system tends to have enough strength as a diaphragm to transfer load to the other columns until you get a pancake failure. The only time I see overturned collapses is in a single column system (think blown over wind turbine), strong lateral loading induced failures, or cantilevered structures. For a square tube with gravity loads it is likely to pancake. Quote furthermore, 2-5% eccentricity? Isn't L/500 the standard in AISC 13 at least? BTW it is REALLY hard to try to justify this with facts but it is a bit more fun. 2-5% based on D of the column L/500 for a 10 ft column (0.24 inch) is about the same as 2% of the depth of a W12 column. I figured, but I am already going to be working late tonight because of this so I will have to leave this for now. EDIT - Quote Link to comment Share on other sites More sharing options...
Jimbo_Poke Posted March 10, 2017 Share Posted March 10, 2017 I should also add not just the floor frame, but the stories above are acting almost as a shear wall in ways. In other words, there is a lot going on and the conservative nature of design leads to a lot of redundancy and the load being able to follow stiffness. What there isn't redundancy for in this case is once each column in a floor fails then it is game over. At that moment the weight is coming down pretty much vertical. 1 Quote Link to comment Share on other sites More sharing options...
happycamper Posted March 10, 2017 Author Share Posted March 10, 2017 13 minutes ago, Jimbo_Poke said: Mathcad? I am a consultant in Buffalo, Wyoming we don't have money for mathcad! We got a student version for free at UW *shrugs* IIRC its floating license is cheaper than you'd think 13 minutes ago, Jimbo_Poke said: Yield Strength as a percentage of max yield strength vs Temperature for steel is fairly uniform. In other words 100ksi vs 50 ksi vs 36 ksi will have similar reductions in yield strength percentage wise. Also the difference in grade of different parts of the building likely reflect larger load demands for that portion of the building. Both buildings were subject to similar impact loads and subsequent fires. I would expect similar failure modes. Things may have been different had the planes impacted the corner of one of the buildings. But as yield strength increases the plastic zone decreases and (for prestressing strands at least, 270 ksi yield/rupture) eventually just disappears. 13 minutes ago, Jimbo_Poke said: This is a common perception on collapses. But from my experience with collapsed structures, it just doesn't work out that way most of the time. The floor framing system tends to have enough strength as a diaphragm to transfer load to the other columns until you get a pancake failure. The only time I see overturned collapses is in a single column system (think blown over wind turbine), strong lateral loading induced failures, or cantilevered structures. For a square tube with gravity loads it is likely to pancake. 2-5% based on D of the column L/500 for a 10 ft column (0.24 inch) is about the same as 2% of the depth of a W12 column. I figured, but I am already going to be working late tonight because of this so I will have to leave this for now. Ha! running RISA models with moving loads means on the clock but somewhat idle for 5 minute segments. 8 minutes ago, Jimbo_Poke said: I should also add not just the floor frame, but the stories above are acting almost as a shear wall in ways. In other words, there is a lot going on and the conservative nature of design leads to a lot of redundancy and the load being able to follow stiffness. What there isn't redundancy for in this case is once each column in a floor fails then it is game over. At that moment the weight is coming down pretty much vertical. if the plane had truly hit and damaged the columns, it should have created a localized P delta creating rotation impact wards. After the fires cased those members to further buckle and then weakened the tensile strength of the not impact side, it would have caused a gradual tilt towards the impact side, creating an overturn! And that's as much as I can justify with engineering principles. God I already thought this rabbit hole was stupid and would enjoy eviscerating the "evidence" for it but having to argue for it is only reinforcing my non conspiracy point of view. Quote Remember that every argument you have with someone on MWCboard is actually the continuation of a different argument they had with someone else also on MWCboard. Link to comment Share on other sites More sharing options...