funk de fino
Dreaming of unicorns
- Status
From my time lurking on this forum, it seems that the Official Conspiracy Theorists are just as steadfast in their own views as the religious far-right. Like those that fall into that group, they can interpret their bible - in this case the NIST report, and it's offshoots - and use the contents to 'prove' and reaffirm any objections more questioning, and less gullible minds may raise. Just my 2 cents worth.
eta.. had to get my label right.
eta.. had to get my label right.
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jaydeehess
Penultimate Amazing
,,and by extension a ship on fire cannot sink.
Corsair 115
Penultimate Amazing
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Has Heiwa brought up the density of WTC7 yet? From what I recall density seemed to figure greatly in his argument as to why WTC1 and WTC2 should not have collapsed.
funk de fino
Dreaming of unicorns
I disagree. And I did not need the NIST report to approve of me disagreeing.
For example. Progressive collapse is not a NIST invention. It is a known. When a truther bot tries to argue that this is impossible they are simply wrong and we do not need the NIST report to see this.
When a truther bot says fires in buildings cannot get hot enough to weaken steel. They are wrong and it is not the NIST report that tells us this. It is a known fact from research.
When a truther bot claims that if you drop 1/5 of a building directly on top of the remaining 4/5 from a height of 2 miles and the building should stay intact then they are simply wrong and we do not need NIST to tell us this.
Topic is Why WTC7 should not have collapsed and below are my final comments I have sent to NIST re its report. Now I take 4 weeks off where the air is fresh and full of music, people are friendly, there is no Internet and it is actually quite peaceful.
Submittal of Comments - NIST WTC7 report
Name: Anders Björkman, 6 rue Victor Hugo, F 06240 France
Affiliation: President, Heiwa Co, European Agency for Safety at Sea (address as above)
Contact: +336 61725424, anders.bjorkman@wanadoo.fr
Reference number: 2008/9/001
Date: 9/3/2008
Report Number: NIST NCSTAR 1-9 Volume 2
Page Number: 455-536
Paragraph/Sentence: Chapter 11 - 11.2 ANSYS Model, 11.3 Analysis results
Comment No. 1: In structural damage analysis - as opposite to structural design analysis - it is not load paths of the intact structure that is of interest, but the path of failures from the first small local failure due to a known cause (e.g. fire/heat/thermal expansion) to the end of destruction including all structural failures in between as a consequence of the first, small failure. Such a damage analysis shall identify the critical failure in the path, i.e. could that critical failure be avoided; the destruction would have been arrested there. Most local failures in steel structures luckily do not progress to create a critical failure that causes the complete structure to globally collapse. The destruction is generally arrested long before that.
The NIST WTC7 draft report unfortunately fails to do this proper structural damage analysis:
It is not clear in what order the various local structural failures take place in the ANSYS model, what elements/nodes are affected, details of failure, cause of failure and consequence of failure (serious or can it be ignored?) and how the boundary conditions (loads on columns at floor 16) are affected.
Reason for Comment: The ANSYS model, only 16 floors high in lieu of 47, consists of primary (vertical steel columns connected to ground), secondary (horizontal and sloping steel beams connected to primary parts) and tertiary parts (e.g. floor elements and walls connected to secondary parts; beams) and associated connections, and it is of vital importance to know the order or path of failures. We know that the structure at ambient temperature is very low stressed and thus looks very safe. Purpose of the exercise is to find the critical, proximate failure that caused the collapse.
Fire/heat/thermal expansion may affect a tertiary member that heats up quicker than adjacent secondary members and the local connections may fail and the tertiary part is out of action but it hardly affects the effectiveness of the secondary parts, which of course is verified when the FEA analysis is re-done after each failure. The secondary parts and their connections (bolted or welded) to primary parts are much stronger than those of tertiary parts and will deflect and deform with the primary parts and it is highly unlikely that thermal expansion will produce forces that break the much stronger connections between secondary and primary parts. It is noted that a critical failure mode may be buckling of one primary structure column losing supports by secondary structure floor beams.
Suggestions for Revision: Chapter 11.2 to be expanded with a list of all local failures in order of occurrence with details and seriousness as outlined above in Comment No. 1. After each failure the condition of the model is evidently re-analysed by FEA and the results of each element (primary, secondary and tertiary) summarized in Chapter 11.2. Doing that we will know when the situation becomes really serious, e.g. when/if a primary part starts to get affected. Evidently a global collapse is only possible if primary structural parts are affected and we are interested in all local failures leading to that critical failure; the proximate cause of collapse. The draft report Chapter 11 is incomplete in this respect.
Example how to improve the report:
1. Tertiary structural elements connected to a floor beam fail due heat/thermal expansion. These failures/causes are easy to list.
2. Secondary structural elements (beams with or w/o floor elements) connected to a column fail. These failures and their causes should also be easy to list, but here the explanations must be more complete. If, e.g. a beam connection to the column becomes disconnected, we must know exactly how and why (because you do not expect that to happen).
3. Primary structural elements (e.g. column 79) fail. If cause of failure is buckling due to loss of supports of secondary floor beams (and not thermal expansion), say so, but explain how many secondary structural beams must fail before the critical failure of the primary column becomes imminent. This failure to a column evidently affects the boundary conditions, so you have to move on the next model to find out what really happens outside the model.
Unfortunately you do not know if this failure of a column in the ANSYS model is the critical one, as you do not know what happens above floor 16. Evidently a failed column cannot carry any load, so either the load carried drops off or is transmitted to other elements, but in either case the boundary conditions changes; the loads applied at floor 16 change!
It would be very easy to extend the ANSYS model to 47 floors to solve that uncertainty. Then you can see how each failure below floor 16 affects the load distribution above floor 16. Thus it is suggested that the ANSYS model is also extended to floor 47 in your final analysis/report.
Report Number: NIST NCSTAR 1-9 Volume 2
Page Number: 537-600
Paragraph/Sentence: Chapter 12
Comment No. 2: The LS-DYNA 47 floors model is very big with >3 million elements and >3.5 million nodes and the data of a partly damaged ANSYS model incl. boundary conditions is copy/pasted into it to represent the starting (stable?) condition with local damages below floor 16. As shown in Comment No. 1 the details of the damaged ANSYS model are not clear and it is not certain, if it represents a realistic starting condition. Another question is if you can copy/paste data of a locally damaged structure into an undamaged one? What about the boundary conditions at floor 16? Another question is the reliability of the LS-DYNA software. Has it been tested properly? It does not seem to be commercially available.
Reason for Comment: The LS-DYNA, like the ANSYS model, consists of primary (vertical columns connected to ground), secondary (horizontal and sloping beams connected to primary parts) and tertiary parts (e.g. floor and wall elements connected to secondary parts; beams) and associated connections, and it is again of vital importance to know the order or path of failures. We know that the structure at ambient temperature is very low stressed and thus looks very safe.
Heat/thermal expansion may at this time have affected tertiary parts below floor 16, the local connections of which may have failed and the tertiary part is out of action and it has apparently affected the effectiveness of the secondary parts, but the situation is not clear (as Chapter 11 is incomplete). The secondary parts and their connections to primary parts are much stronger than tertiary parts and will deform and deflect with the primary parts and it is highly unlikely that thermal expansion will produce forces that break the connections between secondary and primary parts. However, it is assumed here that some secondary and primary parts below floor 16 have actually failed (causes to be established) and shifted a column (No 79?) out of initial locations affecting the boundary conditions at floor 16, but that the structure below floor 16 is still stable.
It is of vital interest to know how these local failures below floor 16 immediately affect the virtually undamaged structure above, when (A) the analysis starts (how serious are the failures below?) and (B) every further failure that follows below and above floor 16 and finally, (C) at the end, when all parts are rubble.
It is evidently possible that when a primary column fails below floor 16, the load on it is transmitted to adjacent columns via intact structure above floor 16, i.e. the boundary conditions must be modified in the ANSYS model analysis. Was it done?
It is not clear how and why the software LS-DYNA can keep track of parts that are completely disconnected from the structure due to multiple failures.
Suggestion for Revision: The method to copy/paste details of the ANSYS (Chapter 11) model at end of assumed failures below floor 16 produces uncertainties.
It would be better to start afresh with the LS-DYNA model as completely free of failures and then input all the local - serious (?) failures - one by one - as identified in the ANSYS model below floor 16 and listed in Chapter 11.3 and see what happens everywhere at every initial, local failure and then proceed with the further failures, one by one, away from the first local non-critical failures, until the critical failure and its cause are identified.
Chapter 12 thus to be expanded with a list of all further local failures above and below floor 16 in order of occurrence with details and seriousness as outlined above in Comment No. 1. After each failure the condition of the model is evidently re-analysed by FEA and the results of each element (primary, secondary and tertiary) summarized in Chapter 12.4.
Doing that we will know when the situation becomes really serious, e.g. when/if other primary parts (than column no. 79) start to get affected and why and what the real, proximate failure of total collapse is - the critical failure - and when it occurs in the failure path. Looking at the ANSYS model data only, it seems that column 79 could collapse completely due to a known cause (buckling), but that it would be the end of the local (serious) destruction. The other columns should not be affected!
But apparently the failure of column 79 causes further failures of other primary parts and it needs to be explained - the failure path is to be extended. So Chapter 12 must be expanded with details of further failures leading to the final, critical one - the proximate failure initiating the global collapse. Would that proximate failure have been avoided for any reason, the destruction would have stopped then and there.
Example:
4. It is found that primary structural element column no. 79 fails due to buckling.
5. It is further found that this failure (4.) causes identical, mechanical failures to secondary structure (beams) that
6. in turn causes damages to adjacent primary structural columns that fail that
7. in turn causes further failures to secondary structure (beams) that
8. in turn causes damages to adjacent primary structural columns that fail, etc.
The critical failure or failures and its cause (buckling of column no. 79 - failure no. 4 - and unknown effects of the beam(s)) are thus those no. 5 above, as then the global collapse starts. Would that or those failures have been avoided (by clever design?) the global collapse would not have taken place.
Evidently the failures continue, after the critical one has been reached, until total destruction, which of course is of less importance. But it is very good, that you do the analysis to the end; then also details of elements/parts getting completely detached from the structure can be identified (and later be compared with what was found in the rubble) in the report and how these loose parts are assumed to load, slip off or jam the structure after being detached.
Evidently a global collapse is only possible if all primary parts of the structure are affected but we are interested in all local failures leading to the first critical failure that causes/initiates the collapse, e.g. no. 5 in the example above. The draft report is incomplete in this respect and should be expanded.
I am personally quite surprised that the small local failures down below around a few columns are not arrested, when running out energy to produce further failures up top. Just because one or two column fails due to local failures, should not cause other, complete intact columns to fail far away.
Actually, if the LS-DYNA software can produce what is suggested, it should be able to simulate all the structural conditions from (A) the completely intact, prior fire, cold condition, (B) all the part damaged conditions due local failures with still intact structure left including (C) the critical failure condition, when further destruction starts by gravity alone, and not least, (D) the end condition, when all structural parts or sub-assemblies are disconnected in the rubble at equilibrium on the ground.
There are (D) huge blocks of structure in the rubble with broken primary parts (columns). The LS-DYNA software apparently can simulate how these big blocks bounded by failed elements came about, e.g. how the primary columns were sheared off away from bolted and welded connections, and ended up as seen on many photos. It is also a good test to verify the reliability of the LS-DYNA software, details of which are completely unknown to me. (Only reference to LS-DYNA is a user's manual of little value).
If the LS-DYNA software is as good as suggested, it can be used in analysing structural damages in ship collisions and thus improve safety at sea (my principal interest).
Summary of Submittal of Comments
By using two complete (47 floors) models (ANSYS and LS-DYNA) to simulate the failures' path(s) leading to the critical failure initiating collapse, the reliability of the final result will improve.
All failures in the path(s) should be described, particularly when secondary and primary structural elements start to fail and the status (stress or FoS levels) of the structure after each failure.
The critical failure, e.g. the failure of a secondary structural element - a beam, that initiates the global collapse, must be described in detail and how it can affect undamaged remote structure, i.e. other primary columns, by e.g. load transfers as calculated by the software.
As load transfers are only possible via secondary structure and connections, you wonder why not only those secondary parts fail, leaving the intact primary structure unloaded and unaffected (as they are also connected/supported by other beams that do not fail), i.e. the report must clearly explain why WTC7 collapsed like a house of cards that has never happened before.
End
Submittal of Comments - NIST WTC7 report
Name: Anders Björkman, 6 rue Victor Hugo, F 06240 France
Affiliation: President, Heiwa Co, European Agency for Safety at Sea (address as above)
Contact: +336 61725424, anders.bjorkman@wanadoo.fr
Reference number: 2008/9/001
Date: 9/3/2008
Report Number: NIST NCSTAR 1-9 Volume 2
Page Number: 455-536
Paragraph/Sentence: Chapter 11 - 11.2 ANSYS Model, 11.3 Analysis results
Comment No. 1: In structural damage analysis - as opposite to structural design analysis - it is not load paths of the intact structure that is of interest, but the path of failures from the first small local failure due to a known cause (e.g. fire/heat/thermal expansion) to the end of destruction including all structural failures in between as a consequence of the first, small failure. Such a damage analysis shall identify the critical failure in the path, i.e. could that critical failure be avoided; the destruction would have been arrested there. Most local failures in steel structures luckily do not progress to create a critical failure that causes the complete structure to globally collapse. The destruction is generally arrested long before that.
The NIST WTC7 draft report unfortunately fails to do this proper structural damage analysis:
It is not clear in what order the various local structural failures take place in the ANSYS model, what elements/nodes are affected, details of failure, cause of failure and consequence of failure (serious or can it be ignored?) and how the boundary conditions (loads on columns at floor 16) are affected.
Reason for Comment: The ANSYS model, only 16 floors high in lieu of 47, consists of primary (vertical steel columns connected to ground), secondary (horizontal and sloping steel beams connected to primary parts) and tertiary parts (e.g. floor elements and walls connected to secondary parts; beams) and associated connections, and it is of vital importance to know the order or path of failures. We know that the structure at ambient temperature is very low stressed and thus looks very safe. Purpose of the exercise is to find the critical, proximate failure that caused the collapse.
Fire/heat/thermal expansion may affect a tertiary member that heats up quicker than adjacent secondary members and the local connections may fail and the tertiary part is out of action but it hardly affects the effectiveness of the secondary parts, which of course is verified when the FEA analysis is re-done after each failure. The secondary parts and their connections (bolted or welded) to primary parts are much stronger than those of tertiary parts and will deflect and deform with the primary parts and it is highly unlikely that thermal expansion will produce forces that break the much stronger connections between secondary and primary parts. It is noted that a critical failure mode may be buckling of one primary structure column losing supports by secondary structure floor beams.
Suggestions for Revision: Chapter 11.2 to be expanded with a list of all local failures in order of occurrence with details and seriousness as outlined above in Comment No. 1. After each failure the condition of the model is evidently re-analysed by FEA and the results of each element (primary, secondary and tertiary) summarized in Chapter 11.2. Doing that we will know when the situation becomes really serious, e.g. when/if a primary part starts to get affected. Evidently a global collapse is only possible if primary structural parts are affected and we are interested in all local failures leading to that critical failure; the proximate cause of collapse. The draft report Chapter 11 is incomplete in this respect.
Example how to improve the report:
1. Tertiary structural elements connected to a floor beam fail due heat/thermal expansion. These failures/causes are easy to list.
2. Secondary structural elements (beams with or w/o floor elements) connected to a column fail. These failures and their causes should also be easy to list, but here the explanations must be more complete. If, e.g. a beam connection to the column becomes disconnected, we must know exactly how and why (because you do not expect that to happen).
3. Primary structural elements (e.g. column 79) fail. If cause of failure is buckling due to loss of supports of secondary floor beams (and not thermal expansion), say so, but explain how many secondary structural beams must fail before the critical failure of the primary column becomes imminent. This failure to a column evidently affects the boundary conditions, so you have to move on the next model to find out what really happens outside the model.
Unfortunately you do not know if this failure of a column in the ANSYS model is the critical one, as you do not know what happens above floor 16. Evidently a failed column cannot carry any load, so either the load carried drops off or is transmitted to other elements, but in either case the boundary conditions changes; the loads applied at floor 16 change!
It would be very easy to extend the ANSYS model to 47 floors to solve that uncertainty. Then you can see how each failure below floor 16 affects the load distribution above floor 16. Thus it is suggested that the ANSYS model is also extended to floor 47 in your final analysis/report.
Report Number: NIST NCSTAR 1-9 Volume 2
Page Number: 537-600
Paragraph/Sentence: Chapter 12
Comment No. 2: The LS-DYNA 47 floors model is very big with >3 million elements and >3.5 million nodes and the data of a partly damaged ANSYS model incl. boundary conditions is copy/pasted into it to represent the starting (stable?) condition with local damages below floor 16. As shown in Comment No. 1 the details of the damaged ANSYS model are not clear and it is not certain, if it represents a realistic starting condition. Another question is if you can copy/paste data of a locally damaged structure into an undamaged one? What about the boundary conditions at floor 16? Another question is the reliability of the LS-DYNA software. Has it been tested properly? It does not seem to be commercially available.
Reason for Comment: The LS-DYNA, like the ANSYS model, consists of primary (vertical columns connected to ground), secondary (horizontal and sloping beams connected to primary parts) and tertiary parts (e.g. floor and wall elements connected to secondary parts; beams) and associated connections, and it is again of vital importance to know the order or path of failures. We know that the structure at ambient temperature is very low stressed and thus looks very safe.
Heat/thermal expansion may at this time have affected tertiary parts below floor 16, the local connections of which may have failed and the tertiary part is out of action and it has apparently affected the effectiveness of the secondary parts, but the situation is not clear (as Chapter 11 is incomplete). The secondary parts and their connections to primary parts are much stronger than tertiary parts and will deform and deflect with the primary parts and it is highly unlikely that thermal expansion will produce forces that break the connections between secondary and primary parts. However, it is assumed here that some secondary and primary parts below floor 16 have actually failed (causes to be established) and shifted a column (No 79?) out of initial locations affecting the boundary conditions at floor 16, but that the structure below floor 16 is still stable.
It is of vital interest to know how these local failures below floor 16 immediately affect the virtually undamaged structure above, when (A) the analysis starts (how serious are the failures below?) and (B) every further failure that follows below and above floor 16 and finally, (C) at the end, when all parts are rubble.
It is evidently possible that when a primary column fails below floor 16, the load on it is transmitted to adjacent columns via intact structure above floor 16, i.e. the boundary conditions must be modified in the ANSYS model analysis. Was it done?
It is not clear how and why the software LS-DYNA can keep track of parts that are completely disconnected from the structure due to multiple failures.
Suggestion for Revision: The method to copy/paste details of the ANSYS (Chapter 11) model at end of assumed failures below floor 16 produces uncertainties.
It would be better to start afresh with the LS-DYNA model as completely free of failures and then input all the local - serious (?) failures - one by one - as identified in the ANSYS model below floor 16 and listed in Chapter 11.3 and see what happens everywhere at every initial, local failure and then proceed with the further failures, one by one, away from the first local non-critical failures, until the critical failure and its cause are identified.
Chapter 12 thus to be expanded with a list of all further local failures above and below floor 16 in order of occurrence with details and seriousness as outlined above in Comment No. 1. After each failure the condition of the model is evidently re-analysed by FEA and the results of each element (primary, secondary and tertiary) summarized in Chapter 12.4.
Doing that we will know when the situation becomes really serious, e.g. when/if other primary parts (than column no. 79) start to get affected and why and what the real, proximate failure of total collapse is - the critical failure - and when it occurs in the failure path. Looking at the ANSYS model data only, it seems that column 79 could collapse completely due to a known cause (buckling), but that it would be the end of the local (serious) destruction. The other columns should not be affected!
But apparently the failure of column 79 causes further failures of other primary parts and it needs to be explained - the failure path is to be extended. So Chapter 12 must be expanded with details of further failures leading to the final, critical one - the proximate failure initiating the global collapse. Would that proximate failure have been avoided for any reason, the destruction would have stopped then and there.
Example:
4. It is found that primary structural element column no. 79 fails due to buckling.
5. It is further found that this failure (4.) causes identical, mechanical failures to secondary structure (beams) that
6. in turn causes damages to adjacent primary structural columns that fail that
7. in turn causes further failures to secondary structure (beams) that
8. in turn causes damages to adjacent primary structural columns that fail, etc.
The critical failure or failures and its cause (buckling of column no. 79 - failure no. 4 - and unknown effects of the beam(s)) are thus those no. 5 above, as then the global collapse starts. Would that or those failures have been avoided (by clever design?) the global collapse would not have taken place.
Evidently the failures continue, after the critical one has been reached, until total destruction, which of course is of less importance. But it is very good, that you do the analysis to the end; then also details of elements/parts getting completely detached from the structure can be identified (and later be compared with what was found in the rubble) in the report and how these loose parts are assumed to load, slip off or jam the structure after being detached.
Evidently a global collapse is only possible if all primary parts of the structure are affected but we are interested in all local failures leading to the first critical failure that causes/initiates the collapse, e.g. no. 5 in the example above. The draft report is incomplete in this respect and should be expanded.
I am personally quite surprised that the small local failures down below around a few columns are not arrested, when running out energy to produce further failures up top. Just because one or two column fails due to local failures, should not cause other, complete intact columns to fail far away.
Actually, if the LS-DYNA software can produce what is suggested, it should be able to simulate all the structural conditions from (A) the completely intact, prior fire, cold condition, (B) all the part damaged conditions due local failures with still intact structure left including (C) the critical failure condition, when further destruction starts by gravity alone, and not least, (D) the end condition, when all structural parts or sub-assemblies are disconnected in the rubble at equilibrium on the ground.
There are (D) huge blocks of structure in the rubble with broken primary parts (columns). The LS-DYNA software apparently can simulate how these big blocks bounded by failed elements came about, e.g. how the primary columns were sheared off away from bolted and welded connections, and ended up as seen on many photos. It is also a good test to verify the reliability of the LS-DYNA software, details of which are completely unknown to me. (Only reference to LS-DYNA is a user's manual of little value).
If the LS-DYNA software is as good as suggested, it can be used in analysing structural damages in ship collisions and thus improve safety at sea (my principal interest).
Summary of Submittal of Comments
By using two complete (47 floors) models (ANSYS and LS-DYNA) to simulate the failures' path(s) leading to the critical failure initiating collapse, the reliability of the final result will improve.
All failures in the path(s) should be described, particularly when secondary and primary structural elements start to fail and the status (stress or FoS levels) of the structure after each failure.
The critical failure, e.g. the failure of a secondary structural element - a beam, that initiates the global collapse, must be described in detail and how it can affect undamaged remote structure, i.e. other primary columns, by e.g. load transfers as calculated by the software.
As load transfers are only possible via secondary structure and connections, you wonder why not only those secondary parts fail, leaving the intact primary structure unloaded and unaffected (as they are also connected/supported by other beams that do not fail), i.e. the report must clearly explain why WTC7 collapsed like a house of cards that has never happened before.
End
Travis
Misanthrope of the Mountains
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Never mind, Funk beat me to it.
Last edited:
Seymour Butz
Muse
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Quick question:
I'm having a discussion with a troofer at ATS, who also happens to be a PE.
He says that the heating of the floor beams would have "pushed" the girder laterally, resulting in it buckling.... and so how could this result in a connector failure.
I've asked him why wouldn't the buckling of the girder result in connector failure, since I would think that a direct consequence of the girder buckling like he suggests would result in a gross misalignment of the connector, which could easily result in either bolt shear or a flange tear-out. I've asked him if there is something that I'm unable to fathom that would prevent a connector failure as I suggest.
He refuses to give a straight answer.
Am I correct in my assumptions? And he's just dodging?
I'm having a discussion with a troofer at ATS, who also happens to be a PE.
He says that the heating of the floor beams would have "pushed" the girder laterally, resulting in it buckling.... and so how could this result in a connector failure.
I've asked him why wouldn't the buckling of the girder result in connector failure, since I would think that a direct consequence of the girder buckling like he suggests would result in a gross misalignment of the connector, which could easily result in either bolt shear or a flange tear-out. I've asked him if there is something that I'm unable to fathom that would prevent a connector failure as I suggest.
He refuses to give a straight answer.
Am I correct in my assumptions? And he's just dodging?
Newtons Bit
Penultimate Amazing
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He's assuming that the connector is stronger than the buckling strength of the beam in compression, this is false.
Seymour Butz
Muse
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So his whole point is wrong then?
The girder's connector would have failed before the girder buckles?
Is this documented by NIST too, so i can throw it in his face?
Newtons Bit
Penultimate Amazing
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- Apr 12, 2007
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- 10,049
So his whole point is wrong then?
The girder's connector would have failed before the girder buckles?
Is this documented by NIST too, so i can throw it in his face?
Ask him for calcs. This is a very quantative claim and should be proven by established methods. And honestly, the procedure for calculating connection strength and the buckling strength of the column are SIMPLE. If he refuses to do the calcs then he's hiding something.
Grizzly Bear
このマスクに&#
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So his whole point is wrong then?
The girder's connector would have failed before the girder buckles?
Is this documented by NIST too, so i can throw it in his face?
There's a thread somewhere in this forum where a CT'r posted pictures of WTC 7 debris before cleanup got underway which ironically you could possibly use to corroborate it, though to my knowledge the pictures in question aren't in NIST (correct me if I happen to be mistaken). NIST I vividly recall shows pictures of columns which suffered bolt failure as well. NCSTAR1-3 if I recall correctly.
Newton's Bit... sorry to ask you this, I'm not as in tuned to the terminology so forgive me if the question is somewhat rhetorical, I assume you're referring to the issue that the connections are most commonly the weakest parts correct?
Newtons Bit
Penultimate Amazing
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The connection is always the weakest part of the structure except in seismic resisting systems.
Can you explain this a bit more? 1/5 of the building may well have progressively (albeit rather suddenly) collapsed onto the remaining 4/5, but I don't understand the 'dropping a building from a height of 2 miles' reference.
Disbelief
Illuminator
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- 3,607
Something that Heiwa said in other threads.
@NB I have seen manufacturing tools tear apart because someone calculated the strength of a component and not the connectors. Pretty ugly when the bolts shear when they were stressed way over their capacity.
uruk
Philosopher
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- 5,311
Have you considered that maybe a series of small failures can add up to total failure?
The fires cause a structural failure which places the mass of the upper floors in motion.
Now consider the action of the mass of the upper floors in motion impacting on the floor below it. Now consider that the mass in motion is increasing as you go from floor to floor.
Now consider that the structural support the lower floor gained from the upper floor no longer being there because the upper floor has become dissconnected from the lower floor and is now in motion.
Have you also considered the effects of age on the structure? Years of flexation caused by winds?
Seymour Butz
Muse
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Never gonna happen.
He's quite the snake that way. I give him data from the NIST, and he refuses to do any, cuz he can't verify them as NOT being forged, etc. But at the same time he says he has doubts about the collapses... he's even said that he believes thermate was used. But when i ask how he as a structural engineer, can doubt the NIST report - when as he admits, he doesn't have structural documents - his next line is along the lines that why is NIST not releasing the docs. To which I reply that private property laws prevents that....... and on and on.
Interestingly, I asked about connectors failing before buckling and he came up with the claim that buildings in NYC are engineered for "massive" earthquakes. The guy's woo is strong, no doubt about it.
But at the same time, he claims to be a fencesitter.
Close. What it would actually be like is training an athlete to run the 100 metres, shooting in the knee just before the race and then declaring she has failed to run the 100 metres because she didn't make it to the other end. Which would be absolutely true. It is irrelevant to the logic why the column failed or if it was the cause of the tower's collapse, all that matters for this point is that the column clearly did fail, therefore claiming that it didn't fail is really, really stupid.
Cuddles said:
Yes, but evidently hordes of curious children flock there for answers about why the towers couldn't have collapsed and to download instructions for how to perform lethally unsafe experiments.
Respectfully,
Myriad
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