| Welcome! You're currently viewing our forum as a guest. This means you are limited to certain areas of the board and there are some features you can't use. If you join our community, you'll be able to access member-only sections, and use many member-only features such as customizing your profile, sending personal messages, and voting in polls. Registration is simple, fast, and completely free. Join our community! |
- Pages:
- 1
- 2
| Inward Bowing; interesting videos | |
|---|---|
| Topic Started: Mar 24 2008, 01:45 PM (1,128 Views) | |
| exponent | Mar 27 2008, 09:06 AM Post #26 |
|
I'm sorry, are you seriously complaining here that I am pointing you to a source to answer your question? Honestly you've asked a question which is better answered by an authoritative source and I have provided references to them. This is good practise and it is wise to avoid making claims you are not qualified for, therefore I have linked to people who are. How are you possibly finding fault with this? Yes if the answer is in the NIST report or has been given by a qualified engineer then you should go and read that answer! If you have problems with it I am more than happy to discuss it to the best of my ability, but I think you should take a step back here and realise you are complaining that the NIST report has answers. |
 |
 
|
| TDX | Mar 27 2008, 09:56 AM Post #27 |
|
Again-watch this! |
|
|
|
| NK-44 | Mar 27 2008, 11:58 AM Post #28 |
|
I have no problem when you use sources from NIST, quote NB's work, etc. That's what we all do here. I didn't make my point clear. You linked to a paper of NB. I took one point he made and showed that his hasn't considered the heat to have effected the bolts. At least I didn't find such a consideration in his work. Your answer was not to show me that I was wrong and he did indeed consider the heating/weakening of the bolts. Or why it is not important and don't have to be considered. So instead of brining up a point, you just said "read NIST 1-6". Sorry, I ciritizise NB, and you're coming up with "you're debunked, it's all in NIST 1-6". Sorry, but that is not a debate! Do you know what a debate is? If you want to debate the point I made, and you think NIST has answers to my questions, then make specific references, quote it, instead of your "read-NIST" nonsense. That's not a debate when you tell people they have to read something which will take them days or weeks, and then to come back. A debate with such long pauses would be no debate. Got it? If you want to bring in a point, make it! But not "it's in NIST-report", without addressing in specific, what you mean. Your response now shows again that you'r not able to understand how debate works. You say "if the answer is in the NIST report or has been given by a qualified engineer then you should go and read that answer!" Yes, I would read it if you point exactly to where the answer is, or do you really think that every page of the 1-6 report deals with and answers my questions I had reagrding the weakening of bolts? What I expect from you when you participate here is that you do not make general phrases like that, but point to the exact places and quote them (so I do not even expect from you to make it in your own words). And if the passage you want people here to go through is dozens of pages long, then it's up to you to present a summary of the arguments presented. That's how debate works. When people spend hours and hours to read the NIST reports, that's a good thing and recommended, but that is not the debate. Again, if you're not here for debate but for making us aware that the official version could be found in the NIST-reports, then your presence here is entirely needless. |
|
|
|
| Miragememories | Mar 27 2008, 12:56 PM Post #29 |
|
I disagree with your 'adopted' position Exponent. If the trusses took on the characteristics of a chain, they would indeed create a pull-in force on the vertical points that connect them. If the trusses somehow shortened, they would indeed create a pull-in force on the vertical points that connect them. Trusses subjected to heat and induced to begin sagging are effectively growing longer as the length between their vertical connection points increases proportionately with the amount of sag. This however does not mean the trusses have lost enough rigidity to give them the characteristic of a chain. The sagging trusses are still resisting lateral forces and are not "pulling" which is the result of completely losing rigidity. We pull when we collapse and are no longer able to push. MM Edited by Miragememories, Mar 27 2008, 01:23 PM.
|
|
|
|
| exponent | Mar 28 2008, 07:08 AM Post #30 |
|
Like I have said, this is how I started out originally but with a few rather pointless times spent looking up a large amount of references I grew tired of it. The actual reference you're looking for starts in NCSTAR 1-6C on page 39.
That's not actually true and published debates / correspondence debates occur all the time, but regardless I have provided you the reference which I am more than happy to do, but let my explain my point. This answer is in NCSTAR 1-6C. It took me approximately 10 minutes to find this again. What I am trying to suggest is that you should be very familiar with this particular section as with the rest of the NIST report. It is a very important document and it is imperative that anyone debating the 'official version' should have a very good idea of their results. That is why I wish to ensure you have read it in total. If you want me to provide a specific reference, I am more than happy to do so (as you can see above).
I can only defer to NIST for this MM, they calculated that the upper truss chord entered tension completely, giving it the chain characteristics I am referring to. For actual calculations to this extent I would talk to Newtons Bit, it's possible you need FEA to be able to answer this too. |
|
|
|
| Stundie | Mar 28 2008, 07:36 AM Post #31 |
|
One thing I wanted to mention, but I'm not sure if this has been addressed or not. So forgive me for looking stupid if this as been addressed and explained. But the perimeter columns which appear to be bowing inwards? Wouldn't this be the result of the force from the planes impacting the perimeter columns?? |
|
|
|
| Miragememories | Mar 28 2008, 11:44 AM Post #32 |
|
Well we could all defer to NIST and NB and I'm sure that is your preference. If you can only offer referrals and have no interest in thoughtful discussion, then I think your job was done long ago. What is so difficult to comprehend about my explanation regarding the forces at play on the trusses? We know they don't add any additional weight load to the columns as a result of heat. We know that they have to lose all rigidity before they behave like a chain, hanging from their connection points and 'pulling'. If you apply force to both ends of a chain, it won't resist. If you apply force to both ends of a truss that is expanded by heat and exhibiting sag, it will still continue to "push back", or if you use enough force, it will "bend". It makes no sense that a solid static object can "push" and "pull" at the same time. There is no evidence that the trusses were heat softened to the point that they lost all rigidity and behaved like hanging chains. MM Edited by Miragememories, Mar 28 2008, 01:13 PM.
|
|
|
|
| exponent | Mar 29 2008, 09:11 AM Post #33 |
|
Nothing is difficult to comprehend MM, but my uninformed speculation would be pointless. I would rather not comment on what is quite a complex behaviour without being at least reasonably sure I understand it. I have asked Newtons Bit to weigh in as he does this sort of thing for a living and is better informed as to the forces involved. edit: If you truly believe there's no evidence this occured, what caused the perimeter walls to pull inwards? Edited by exponent, Mar 29 2008, 09:12 AM.
|
|
|
|
| NK-44 | Mar 29 2008, 11:09 AM Post #34 |
|
Yes, I don't get this, too. That the floors sagged does not mean they were not under tension anymore. Instead the sagging is the result of tension, of ex-tension. That the floors sagged does not mean they stopped to push against the columns. So the "pull-in forces", the load of the floor pulling in the columns, would be countered by the "pushing forces" of the expanding floor. Which reduces the probability of pulling in. So yes, from what I undertsand, they pulled and pushed at the same time.
In other words, you do not even understand the theory you're defending here.
Are you playing dumb? Please go again to the beginning of this thread and try to understand. Is not really hard to get it. |
|
|
|
| NK-44 | Mar 29 2008, 04:12 PM Post #35 |
|
Please note also this post from another thread. |
|
|
|
| Miragememories | Mar 29 2008, 05:25 PM Post #36 |
|
So you're saying that lay people such as ourselves, can't have a legitimate discussion about logic-based questions regarding theories which have become public policy? I'm just asking you to consider what I am saying, or shoot me down when I'm wrong, or don't make sense. You're wrong, or, at least I believe you are, about this subject involving physical behavior that is far too complex for us to attempt an understanding. We're able to discuss this subject because it doesn't involve a 'too complex' behavior mechanism at all. It's partly a matter of examining what happened 'close up', step by step. We know; Length of steel truss connected at two very solid anchor points. Constant lateral force from outside wind loading. Any 'laterally unsupported', perimeter columns would be subject to possible 'indenting' from ever present variable wind-loading forces. Of course this 'would be' perimeter column 'indenting', would be particularly likely to occur if additionally subjected to NIST's 'theorized' inside 'pulling forces'. NIST could only consider the 'steel' connecting the 'perimeter columns to the core columns' as a 'pull source', so the steel trusses performed that function. NIST required a cause mechanism and without a 'pull source' they could never explain how their final collapse theory works. The problem with NIST's 'pull source', is that it doesn't make much sense and it ignores other more plausible "pull-source scenarios". Any massive aircraft impact damage to the 'perimeter core columns' causing broken truss connections, would certainly place major 'torque' on the trusse's connection points and 'pull-in' on the outside perimeter columns they were attached to. Perimeter core columns, that were effected by the impacting aircraft, would tend to be 'pushed in' to varying degrees, if not severed. Pushing these columns in, would also pull-in the connection to their attached trusses and thus pull-in, or sever the connection to their attached perimeter column. In either case, the condition has been met for indenting the perimeter. Just about any significant structural change in the core will get reflected in the outer perimeter because they are so rigidly connected. Of course heat on the trusses would make them try and 'expand' which is what heated steel does. Structural steel has a Coefficients of Thermal Expansion factor of 12. As a comparison graphite is 0.5 and water to ice is 51. When this steel truss heat-expansion is resisted by the perimeter and core columns, the trusses would be forced to 'bend' downwards in the direction of their weaker, more heat-softened side. Growing longer and bending downwards does not equate to a complete loss of the steel truss's 'push back strength'. When the steel truss, at it's weakest point, becomes too heat-softened to push back, it has attained the 'zero push back strength' of a hanging chain, and would only then, 'pull' with the weight of a truss chain. You simply can't push if you are trying to pull. The two forces (push and pull) can be exercised on the truss, but the 'push tension' or 'rigidity' would remain in the steel unless extremely softened by massive heat. To achieve 'pulling', requires too high a temperature, lasting enough time to soften a steel truss to the point that it loses all it's 'push back tension'. The Truss would then give in to gravity's 'pull' , only now becoming the only force in effect on the truss. Are you saying you believe those trusses really got that hot? MM Edited by Miragememories, Mar 30 2008, 04:33 PM.
|
|
|
|
| Headspin | Mar 29 2008, 05:47 PM Post #37 |
|
is there actually any evidence for floor sag? or is this just a hypothesis? |
|
|
|
| exponent | Mar 31 2008, 10:29 AM Post #38 |
|
No not at all, simply that I was not comfortable with discussing the behaviour of trusses as I know they behave complexly and my knowledge of them is not extensive.
Well that's fair enough, and I will do my best, but please understand that as any sort of 'defender' of the official story here I probably don't know enough to be able to make reasonable assumptions. Don't take what I say as gospel.
I didn't mean that the behaviour was too complex to discuss and I hope I have clarified that.
I honestly doubt it, unless they were entirely unsupported over a several floor section, wind loading is a relatively low amount of force compared to the compressive resistance of the floors. Not to mention we should see huge amounts of smoke movement around said indent. I think winds were relatively low throughout the day though and we can likely discard this for modelling simplicity.
As a tangent, maybe my English is not as good as I thought (not very good anyway!) but I am fairly sure you don't need to put single quotes around 'would be' or 'theorized'. You may be able to correct me here and I am more than happy to hear it 
I'm not entirely sure what you're referring to when you say 'perimeter core columns'. If you are referring to the core columns to which trusses were attached then I don't entirely disagree, but I don't think it could have caused the effects shown. If said trusses were disconnected, they would not fall all the way to the next floor (like in that damn PBS video lots of people laugh at). They were supported by bridging trusses and two way trusses in sections. Regardless they would create a moment around their hinge on the perimeter walls, but there would be no way to develop the magnitude of forces required for the perimeter pull in (6kips).
Indeed it would, and NIST predicts a core column sag (in WTC2, but in worst case) of about 12". Even in the worst case scenario though the core columns would surely have to move by almost 5 feet to develop a 55" inward pull with no truss sagging. This would require an incredible amount of distortion caused by an unknown force.
I disagree, we certainly both agree the effects you listed can take place, but Newtons Bit has already done the pull in calculations for severed core columns and the resulting moments and this is likely the most optimistic for your first theory. The total magnitude of the indentation was around an inch if I remember correctly. Why do you find either of these more plausible than the truss flooring sagging? There seems a lot more cause to believe the trusses would sag, we know they're involved in fire, we know how lightweight they were and we know that even in a reduced scale test with full fireproofing the trusses will sag. We don't really have any such evidence suggesting the core is as responsible, although like I said I don't doubt both behaviors you described occured on a more limited scale.
I think you are entirely correct here, I am not sure of your terms ('push back strength' has no strict definition) but I think you're saying that as the truss sags, the resistance to thermal expansion leads to an increase in compression and as a result an increase in deflection. I entirely agree that this took place, but I think you make a little bit of a mistake in the next section.
Now I don't know exactly how you're using 'heat softened' here so I shall explain the mechanism as I understand it. Trusses are designed to have a top chord in compression, a bottom chord in tension and alternating diagonal elements in compression or tension. As the truss heats, tension in the bottom chord and eventually the diagonal elements become unable to resist the compressive or tensile forces. In the case of the bottom chord its length increases and results in less resistance to sagging caused by the compression of the top chord. As the truss gets hotter the diagonal elements begin to buckle or lengthen under the forces and at some point they become too weak to restrain the upper chord at all. At that point the upper chord can sag far enough that there is no restraint being provided by any other element and it can slip into tension. Where we disagree here is that I see the pull in forces and 'push back forces' as a combination of elements. In a theoretical example, suppose you were to extract a single truss at a point before the upper chord is in tension. As you try to move the two truss ends closer together, this is resisted not only by the upper chord in compression, but also the lower chord in tension and the diagonal elements as their compression increases. If you vary the temperature of the truss the compression element of the upper chord will likely not vary much I believe but the lower chord's tension component certainly will. This is why I am rather hesistant to reply to your claims, my understand of truss structures indicates to me that the action is more complex than simply compressing or bending an element.
Of course, if you really doubt trusses could be heated to that extent please have a look at the Cardington fire test data. Steel heats up really quickly in fire, and temperatures of 700c were attained within 15 minutes with the same fuel load iirc (I have some graphs I can post if you really like). Anyway I am sure there'll be points at which we disagree, but i want to point out again I am not committed to any theory of truss behaviour here, my knowledge is limited and I wish it to be expanded. |
|
|
|
| Miragememories | Apr 1 2008, 02:05 PM Post #39 |
|
I meant the outer core columns that connected with the trusses. So you don't believe the loss of lateral reinforcement from perimeter disconnected trusses, or the massive torque from core disconnected trusses, could cause the perimeter columns to be indented. Yet you maintain a belief that "pulling" from heat-expanded bowing trusses is quite capable of producing the force necessary to bend those perimeter columns inwards.
I have to take any calculations by Newton's Bit with a "grain of salt". Calculating with limited empirical data is not much more than educated guesswork. I also don't like the implication of the word "sag" which suggests a meaning that does not accurately describe the situation but does reinforce the idea of a pulling force. sag sink or subside gradually under weight or pressure or through lack of strength The truss would 'bend' rather 'sag'. bend shape or force (something straight) into a curve or angle Your belief that the indentation of the perimeter was no more than 1 inch is interesting. This small amount of perimeter column distortion was enough to allow collapse initiation in your opinion? We know the aircraft produced some structural damage to the towers. The kind of damage noted, represents reasonable expectations, though the severity of the damage is up for debate.. We don't know with much certainty how much damage the fires created. The bending trusses are a subject of hypothesis and not an observed condition. If the trusses expanded from the heat, as they would be expected to, and the core and perimeter columns did not bend in response, then the trusses had to bend on their weakest side to accommodate the heat expansion. So in other words, the heat-expanding trusses push against the perimeter and core columns. The perimeter and core columns presumably didn't bend in response and thus effectively pushed back. The trusses outward push was overcome by the greater push back and as a result, they bend down. ==========>>> <====> <<<========== Now as the Official Theory goes, this "==========>>> <====> <<<==========" somehow becomes this "==========>>> ==><== <<<=========="as the heat weakened truss still under much tension from it's natural rigidity, supposedly stops pushing back and starts pulling. I simply see no argument, or science, that backs this notion that the truss will start "pulling" as would a loose chain.
What you seem to be accepting is something like an ability to rise, and fall, at the same time. Two opposing forces, transmitted through the same object, yet oddly independent of each other, rather than one dominating the other as would be the logical expectation. ======> vs. <=== equals the resultant ===> What trusses are designed to do and how they actually function, is a product of their particular application. Bridges for instance use trusses extensively and they are designed to deal with both tension and compression forces. The floor trusses inside the tower were required to deal primarily with compression forces, conveying these forces from the wind-loaded outer perimeter to the massive inner core columns. If the perimeter, or core tried to 'pull away' from the truss, opposing tension forces would be created in the steel truss, which due to it's hardness, strength and rigidity, would try to resist, or 'pull back', until the force became so great that it failed at it's weakest point, likely at one of it's end connections. But there was little or no observed evidence suggesting that the perimeter columns were bending out. The trusses were not shown to have been subject to significant outwardly pulling forces that would have caused them to respond with a resisting inward pull. If a truss was subjected to intense cold, a cold isolated from it's perimeters, it would contract and you would have a valid argument for pull-in force from the truss acting on the perimeter column. A truss expanding from heat provides no argument that I can see for creating a new and powerful pull-in force on the perimeter column. The counter force resulting from the column's resistance to bending out, simply forces the truss to bend downward to accommodate it's increased length, but that 'pushed bend' is not a 'pulled bend'. MM Edited by Miragememories, Apr 3 2008, 11:48 AM.
|
|
|
|
| Bananaman | Apr 16 2008, 08:46 AM Post #40 |
|
Just trolling by
|
I do admire your patience, exponent. Personally I think that arguing about what everybody can see with their naked eyes is a bit mind-boggling, but I guess the truthers have to be led through things one step at a time. Personally when I get adequate answers from truthers to the following I'll start listening to their puerile quibbles about bowing. 1. How did the twin towers both manage to collapse from the point of impact if there was skullduggery involved? 2. How did men in dark glasses and suspicious outfits rig the building for demolition without anyone noticing? 3. Why do the twin towers collapse neither look nor sound like a demolition. Balls in your court, truthers. I'm so glad I'm not living in your fantasy world. Bananaman. |
|
|
|
| JFK | Apr 16 2008, 09:14 AM Post #41 |
|
1. How do you know the collapses were initiated at the point of impact ? Did you witness it firsthand ? What I am getting at is if a section of core 3 - 5 meters in height was blown laterally well below the collapse zone would the collapse look any different than it did ? 2. a. ) why would they need dark glasses ? b. ) why would they need suspicious outfits ? c. ) disguised as maintance workers doing a wiring upgrade would give them all the access they would need. 3. For a demolition of 2 nearly quarter mile high buildings it looked like a job very well done. The majority of the sound would have been masked by falling and colliding steel. How many structures of that height have you seen demolished ? My point is that they took extraordinary engineering skills to construct them, why should they not take extraordinary demolition skills to demolish them ? My turn to ask questions. 1. Had it been a real terrorist attack do you not think they would have waited another hour or so so everyone would be at work and hit the buildings lower with those planes ? 2. If they attacked us because they hate our freedoms, would they have not picked more appropriate targets like for instance the statue of Liberty ? 3. Why was the Patriot act already written prior to the attacks ? Balls in your court, skeptics. I'm so glad I'm not living in your fantasy world. JFK. |
|
|
| look-up | Apr 16 2008, 09:21 AM Post #42 |
|
I think what is missing from this argument is the truism that, if the floors were sagging, they MUST have been severed from the core columns already. Also... That the inward force exerted by a sagging floor onto an exteriror collumn, would probably be compensated by the floors directly a bove or below. In other words, for an exterior column to be pulled inward, (which isn't what we see in the collapse footage. instead we see ejection of mass, i.e. explosions) it would have to also pull the floors above and below inward, meaning that those floor trusses would also have to be damaged and ineffective at holding all of the columns in place. As anyone with a minute amount of physics knowledge knows, the columns don't just hold the floors in place... but the floors help to keep the columns in place as well. In other words, every action has an equal and opposite reaction. As the floors sit in place, they hold the walls in place, and vice versa. If one or two floors sag and pull the exterior inward, it would only be possible if the exterior columns were severed from the adjacent floors as well. It is likely that the impacted floors were punctured (for lack of a better word), and of course those broken floors would sag. The question is, does that equal enough force to break ALL of the exterior columns that were left over AND the remaining of 47 core columns? I seriously doubt it. I could imagine a situation where falling floors compounded the amoung of force that the next floor would endure, and possible cause perfectly intact floors to collapse. However, it would not be exponential addition of force, as each time a floor was broken, it would use up some of the falling momentum. All of the floors would not have pancaked on their way down, and as we see, they were ejected outward, meaning that they couldn't compound in the way that duh-bunkers would suggest. Even if it DID HAPPEN that way (meaning that the floors sagged and caused collapse initiation, which seems highly unlikely), it would NEVER have happend at anything CLOSE to free fall. Every time another floor needed to break and then fall, would have arrested the descent of the mass (if it was not ejected outward as proven by video footage). |
|
|
|
| Miragememories | Apr 16 2008, 09:40 AM Post #43 |
|
Hani Hanjour apparently was their best pilot when it came to low level attacks. Too funny. MM |
|
|
|
| look-up | Apr 16 2008, 09:46 AM Post #44 |
|
a plane hit the floors. I'm sure that had at least some effect on the trusses themselves. Because the planes were in a bank when they hit, one of them in a pretty severe bank, they probably broke many floors. I hope you agree that planes did indeed hit the towers... But if that force from broken floors were going to pull even more c olumns inward, it would not take 45 min to an hour... the force was changed as soon as the beams and trusses broke. The fires mostly went out after the first 15 min, and thus would have begun cooling soon thereafter. What happened at the 45-60 min mark that made them suddently collapse at near-freefall speeds? Bits and portions of the NIST theory make sense, but when you stitch all of those bits and pieces together, it does not explain the collapse of the buildings we see in those videos. It may someday explain the collapse of some hypothetical building somewhere else, but it does not explain those to precious buildings, that fell on 9/11/2001. Sidenote: Since brittish write dates with the day first, do you also say "11/9" instead of "9/11"? Just curious. |
|
|
|
| Bananaman | Apr 20 2008, 03:05 AM Post #45 |
|
Just trolling by
|
You are joking I hope. Watch the towers fall again on any video you care to look at. Where does it start from? This is almost silly. Actually it is silly.
Do more research. Find out how a demolition of a building is accomplished then come back and reply.
Er, you don't seem to have a clue what you're talking about. Just a hint: world trade centre (big target to fly a jet into with relevance to the western world, or...statue of liberty (small target not relating to the issues at hand which the hijackers had in their minds.). Honestly, this is too easy.
You didn't do much history at school did you? Bananaman. |
|
|
|
| JFK | Apr 20 2008, 04:05 AM Post #46 |
|
So in your little world there is no possibility that the collapse initiated at the core at a lower area than the impact zone ? If you say no I expect see your proof... A video of the perimeter collapsing while the core is not will be fine. sillybananaman. 
Been there done that, have you ?
Erhm... no. The statue of Liberty has been taught to be the symbol of Liberty and Freedom over here in the US.... Even though it is actually the symbol for the whore of babylon, Semeramis, Given to the US by the French Freemasons. Of course in Westminister they ignore that part.
When I was in history class you guys were impleminting the redrawing of your boundaries... Google "Local Government Act 1972".  Thanks for the non answer to that one. That so called Patriot Act undermined everything upon which the United States of America was founded upon in one fell swoop. Do some research and then we *might* talk.... Until then you are just another snot nosed kid who knows nothing... to me.  |
|
|
|
| Bananaman | Apr 20 2008, 12:07 PM Post #47 |
|
Just trolling by
|
I'll reply properly later, sunshine. But I think I know which of us isn't too well informed. You really do make this embarrassingly easy. Bananaman. |
|
|
|
| JFK | Apr 20 2008, 12:32 PM Post #48 |
|
Don't bother... I am not even remotely interested in your drivel. |
|
|
|
| honestjoe | Apr 22 2008, 12:28 AM Post #49 |
|
Hello, If I may I would like to see if I have grasped what is being discussed here. If I make a mistake I would sincerely appreciate if someone will point out my error so that I can correctly understand what caused the collapse. Let me see if I have this right. Your suggesting that: #1 The fire reached temperatures hot enough (1500F) to soften the steel like a caramel truss over a camp fire. “Only three of the recovered samples of exterior panels reached temperatures in excess of 250 C (482 F) during the fires or after the collapse. This was based on a method developed by NIST to characterize maximum temperatures experienced by steel members through observations of paint cracking.” NIST, p. 181 #2 The fires not only reached 1500F but maintained that temperature long enough to turn steel trusses into liquorish. “The initial jet fuel fires themselves lasted at most a few minutes and office material fires would burn out within about 20 minutes in a given location.” (NIST, 2005; p. 179) “None of the recovered steel samples showed evidence of exposure to temperatures above 600 C (1092 F) for as long as 15 minutes.” NIST, p. 180 #3 So the trusses after being exposed to the now maximum 1092*F fire for no more than 15 minutes then began to expand but was stopped by the much stronger and thicker perimeter columns made out of 1,000,000 PSI super-strong steel causing the trusses to sag. NIST exaggerated the temperatures (1300 F), applied these temperatures for 2 hours (i.e. over twice the duration of fires known to have existed in the failure zones), striped all the fireproofing, and then doubled the height of the inward pull zone, and applied triple the weight of what the floors were known to actually be supporting to produce even a hint of bowing from fire. Which was "ONLY" 3 inches! #4 As the trusses began so sag like an oven grill made of plastic they began to pull on the much stronger and thicker perimeter columns made out of 1,000,000 PSI super-strong steel. Column buckling was found to occur when an inward lateral load (pull-in) of approximately 12 kips was applied to three adjacent floor levels. (NCSTAR 1-6 p xlix para1) Column instability (buckling) was reached with a transverse load of 12.6 kips per column. (NCSTAR 1-6 p115 para2) #5 During all of this the 5/8” ASTM A325 bolts had amazingly resisted the heat by some unknown miracle and manged to pull in (because it couldn't push out) the much stronger and thicker perimeter columns made out of 1,000,000 PSI super-strong steel that were designed to withstand gale force winds and a 100yr storm. NIST’s table 4-4 (NCSTAR 1-6 p75) shows that the interior seat capacity against horizontal tensile force is only 9 kips. (So does figure 4-16 NCSTAR 1-6 p78) Thus, we are 3 kips to 3.6 kips away from a working mode of failure. And if you calculate any loss of strength on the thicker "EXTERIOR" columns that same loss would be greater for the smaller 5/8" bolts because they would require less time to heat and would be more exposed to higher temperatures as they were sitting "INSIDE" the supposed oven with no place (cool side) for the heat to dissipate. But even if you could get the much stronger and thicker perimeter columns made out of 1,000,000 PSI super-strong steel to pull in you still are left with an enormous obstacle left in the way of initiating the systematic failure and total collapse because the building could still support its self. The Vierendeel trusses would be so effective, according to the engineers’ calculations, that all the columns on one side of a tower could be cut, as well as the two corners and several columns on the adjacent sides, and th tower would still be strong enough to withstand a 100-mile-per-hour wind.(AND THAT WAS AT THE BOTTOM OF THE BUILDING!) --City in the Sky, p 133 So please, please, please explain why, if it were even remotely possible for the fire to get hot enough for long enough to cause the trusses to sag enough thereby causing the 5/8" bolt to pull in the much stronger and thicker perimeter columns made out of 1,000,000 PSI super-strong steel, would it even matter. How would that initiate systematic and total collapse? What about the other structural members built into the framework to handle those stresses like the additional beams joining the exterior to the core where needed? WHAT ABOUT THE CROSS TRUSSES? |
|
|
|
| 1 user reading this topic (1 Guest and 0 Anonymous) | |
| « Previous Topic · World Trade Center · Next Topic » |
- Pages:
- 1
- 2
11:08 PM Dec 7
