How WTC 7 was pulled down

[Reactor drone]

A 47-story building dropping for a period of free fall, while maintaining a relatively level roofline, requires the near instantaneous removal of all its gravity-resisting vertical support over the distance travelled at free fall speed.

.........

The NIST were forced to concede that 1.75 seconds into global collapse, for 105 feet, 8 stories, the east, north and west faces of WTC 7 were known to be falling in unison at free fall speed. The kinked roofline remained relatively level through this descent, indicating vertical support was removed virtually instantaneously on the east, north and west sides of WTC 7.

The NIST did not update their detailed collapse scenarios to include any reference to this known free fall, so it is unknown how they feel their theory satisfactorily explains how all three sides could agree to fail at the same time.

MM

Do you think that buckling can remove the vertical support or do you feel that the only way to stop a column from providing support is to remove it entirely?

As a simple test, hold a pencil vertical and press down. You'll find it offers a great deal of vertical support but if you tilt the pencil and press down you'll find it offers almost no support.

A wall of columns that has buckled provides negligible vertical support and with the interior of the building (the part that braces the exterior columns in their vertical position) collapsing, the walls become unstable and buckle under the load.

There was no requirement to update the model since the model already showed this type of column buckling.

Meanwhile the alternative position you put forward, that some kind of demolition removed the columns, has no evidence, no model and no plausible explanation as to how the support is removed for eight storeys.

 

[Furcifer]

Before everyone says "so what?", consideration should be given to what free fall entails.

It means when you let fires burn for long enough buildings collapse, fast.

Free fall is exactly what you would expect when a building fails. That's just how it works. End of story. Feel free to show otherwise using science and not your emotions. Thanks

 

[Architect]

Yes and no.

1. Structural failure can be a really rapid event. It all depends (and let me stress this) on the structural system and the failure mode, in particular the scope for redistribution of loads through (say) redundancy. For a lay rendering of this, I will once again commend "Why Buildings Fall Down" to everyone.

2. Freefall (or near freefall) failure may occur in certain collapse patterns, but not all.

I've yet to see a compelling explanation from any of the Truthers as to why half a page of fag-packet calculations based on little or no technical understanding is to be preferred to the voluminous NIST report.

 

[Furcifer]

Yes and no.

1. Structural failure can be a really rapid event. It all depends (and let me stress this) on the structural system and the failure mode, in particular the scope for redistribution of loads through (say) redundancy. For a lay rendering of this, I will once again commend "Why Buildings Fall Down" to everyone.

2. Freefall (or near freefall) failure may occur in certain collapse patterns, but not all.

I've yet to see a compelling explanation from any of the Truthers as to why half a page of fag-packet calculations based on little or no technical understanding is to be preferred to the voluminous NIST report.

No argument here. I think this poster however doesn't have a firm grasp on the basics. The suggested reading order should be "Everything You Wanted To Know About Gravity But Were Afraid To Ask" followed by "Everybody Falls" and finally "Why Buildings Fall Down".

Truthers seem to work from the premise that because it was stationary we need to add up all the reasons to get to free fall. This isn't the case. When things fall down in a gravitational field it's expected to happen at free fall.

It would be so nice if some of these guys would just take the time to learn the basics.

 

[mzelinski]

continuation from posts #151, #215, #252, #333

No it's complete rubbish, and I'm quite certain you know it.

You have to define an equilibrium state for the entire system in order to pursue your analysis. Any thermodynamic potential unaccounted for is more than enough to push the system out of equilibrium and result in increasing entropy. The size of the WTC7, and the simple fact that it's not an isolated system precludes any such analysis.

The kinetic energy available to do work (i.e. structural damage) generated by the thermal expansion is -T*ΔS_internal . In general, this quantity will be only a fraction of the heat influx ΔQ, as is typical of the efficiency of most heat engines. The literature (tribology, metallurgy, etc. often in the context of irreversible thermodynamics) has methods for calculating the internal entropy production.

The maximum possible damage, and therefore the best case scenario for the NIST’s explanation, is when work is treated reversibly. Then, the initial state S_i is the same as the final state S_f (remember, the “final state” being the conveniently chosen end point of the NIST’s phase 2 free fall portion, rather than the total collapsed state of the entire building). In this best case, we would expect to see no more energy than the amount -T*ΔS_internal appear at the output. In real processes, entropy can be added as it propagates, in which case -T*ΔS_internal becomes less negative, in other words less energy is available to do work. This agrees with our intuitive idea of energy dissipating due to friction as it propagates. If -T*ΔS_internal is absorbed by the potential energy of the building before it can do critical damage, then +T*ΔS_internal is transferred to the structure as heat, leaving ΔS_internal < 0 ; the building establishes a new equilibrium and remains stable.

Instead, at the output we see KE_{upper section} . In post # 252 we saw that even when the entire quantity of heat flux into the girder is available to do work, that amount of energy is still orders of magnitude less than KE_{upper section} . And given that the actual quantity that can do damage, -T*ΔS_internal , is only a fraction of the input heat, the disparity between the input and output energy is that much greater. This suggests that a massive amount of energy ΔE = -T_f*ΔS_additional had to have been added to perform the balance of work,

- T*ΔS_internal + ΔE = KE_{upper section} .​

Also, taking into account the relaxation times associated with doing work on materials, it’s unlikely that critical damage could have propagated across the entire building in less than a second, which would have been necessary in order to acheive the collapse’s observed high degree of symmetry.

Putting together posts #151, #215, #252, #333, we should be able to answer the question whether or not the official explanation for the collapse of WTC7 is consistent with the Second Law of Thermodynamics. A similar approach can attempt to answer the same question for the Twin Towers.

 

[twinstead]

Putting together posts #151, #215, #252, #333, we should be able to answer the question whether or not the official explanation for the collapse of WTC7 is consistent with the Second Law of Thermodynamics. A similar approach can attempt to answer the same question for the Twin Towers.

The problem is as a layman, it troubles me that some people (and not just on this forum) whom I trust and have superb qualifications say that you are wrong. This is quite the dilemma. It would be helpful if you could get some kind of respected journal or organization to agree.

 

[Architect]

My goodness, what a load of bollocks!

 

[alienentity]

If only it were that simple, but unfortunately most people seem intent on vesting their faith in the notion that impact damage and fire could make a building come down like like WTC buildings did despite the utter lack of any semblance of experimental confirmation to support such notions.

That's false. There is plenty of experimental confirmation. Please get knowledge. This has already been covered many times, you can read all about the fire science, the models etc...

 

[Newtons Bit]

The kinetic energy available to do work (i.e. structural damage) generated by the thermal expansion is -T*ΔS_internal . In general, this quantity will be only a fraction of the heat influx ΔQ, as is typical of the efficiency of most heat engines. The literature (tribology, metallurgy, etc. often in the context of irreversible thermodynamics) has methods for calculating the internal entropy production.

The maximum possible damage, and therefore the best case scenario for the NIST’s explanation, is when work is treated reversibly. Then, the initial state S_i is the same as the final state S_f (remember, the “final state” being the conveniently chosen end point of the NIST’s phase 2 free fall portion, rather than the total collapsed state of the entire building). In this best case, we would expect to see no more energy than the amount -T*ΔS_internal appear at the output. In real processes, entropy can be added as it propagates, in which case -T*ΔS_internal becomes less negative, in other words less energy is available to do work. This agrees with our intuitive idea of energy dissipating due to friction as it propagates. If -T*ΔS_internal is absorbed by the potential energy of the building before it can do critical damage, then +T*ΔS_internal is transferred to the structure as heat, leaving ΔS_internal < 0 ; the building establishes a new equilibrium and remains stable.

Instead, at the output we see KE_{upper section} . In post # 252 we saw that even when the entire quantity of heat flux into the girder is available to do work, that amount of energy is still orders of magnitude less than KE_{upper section} . And given that the actual quantity that can do damage, -T*ΔS_internal , is only a fraction of the input heat, the disparity between the input and output energy is that much greater. This suggests that a massive amount of energy ΔE = -T_f*ΔS_additional had to have been added to perform the balance of work,

- T*ΔS_internal + ΔE = KE_{upper section} .​

Also, taking into account the relaxation times associated with doing work on materials, it’s unlikely that critical damage could have propagated across the entire building in less than a second, which would have been necessary in order to acheive the collapse’s observed high degree of symmetry.

Putting together posts #151, #215, #252, #333, we should be able to answer the question whether or not the official explanation for the collapse of WTC7 is consistent with the Second Law of Thermodynamics. A similar approach can attempt to answer the same question for the Twin Towers.

Where's the change in potential energy in your equations? Hmm?

 

[excaza]

He is literally just piecing together random

 

[R.Mackey]

Trying to solve this problem using the Laws of Thermodynamics is a crock of crap, and it proves the person saying so knows nothing about statistical mechanics.

The entropy of the system is incredibly difficult to define for something like an entire building. If you don't believe me, try to describe a single macrostate. Go for it.

This approach is valid for things like whether iron will corrode or whether iron crystals will spontaneously form from iron oxide, or whether all the air molecules in a room will decide to stay on one side of the room. The total entropy for a standing vs. collapsed structure is not all that different, because the materials don't change much. Doesn't matter anyway since the building is not a closed system to begin with, so even if it was practical to compute density of states, the equations still don't apply.

Seriously, Truthers, stop misusing Wikipedia. Take a class if you want to know this stuff. Those of us who do can barely summon the energy to laugh at you.

 

[beachnut]

The kinetic energy available...

This is all you got right, and then it went nonsensical. Good luck. Try physics next time.

 

[Dave Rogers]

Putting together posts #151, #215, #252, #333, we should be able to answer the question whether or not the official explanation for the collapse of WTC7 is consistent with the Second Law of Thermodynamics. A similar approach can attempt to answer the same question for the Twin Towers.

Given that your first post on this subject claimed outright that the collapse of WTC7 violated the Second Law, and that you've now retreated to the position that it is in principle calculable whether the collapse of WTC7 violated the Second Law but this has not been done, are you therefore admitting that your initial claim was unsupported by the evidence, and hence a serious error on your part?

Dave

 

[Oystein]

The kinetic energy available to do work (i.e. structural damage) generated by the thermal expansion is -T*ΔS_internal...

You go wrong in the very first sentence, and spiral downward from there.

Thermal expansion does NOT generate the kinetic energy that later does the work we are interested in. Thermal expansion only transfers some of the chemical energy of office contents via the heat of fires into mechanical work at the collapse initiation zone: bending, buckling, and pushing the girder over the cliff.

Once that has happened, gravity and potential energy take over.You have been reminded many times that the big elephant in the room is potential energy, you again fail to consider that energy. Why?

 

[Miragememories]

Do you think that buckling can remove the vertical support or do you feel that the only way to stop a column from providing support is to remove it entirely?

As a simple test, hold a pencil vertical and press down. You'll find it offers a great deal of vertical support but if you tilt the pencil and press down you'll find it offers almost no support.

A wall of columns that has buckled provides negligible vertical support and with the interior of the building (the part that braces the exterior columns in their vertical position) collapsing, the walls become unstable and buckle under the load.

There was no requirement to update the model since the model already showed this type of column buckling.

Meanwhile the alternative position you put forward, that some kind of demolition removed the columns, has no evidence, no model and no plausible explanation as to how the support is removed for eight storeys.

Your example would be fine if it allowed for the lateral bracing provided by all the intact floor systems.

MM

 

[Architect]

Your example would be fine if it allowed for the lateral bracing provided by all the intact floor systems.

MM

That'll be the floors known to have failed around the impact and fire sites, then?

 

[Miragememories]

"Your example would be fine if it allowed for the lateral bracing provided by all the intact floor systems."

"That'll be the floors known to have failed around the impact and fire sites, then?"

Those were hypothesized floor failures.

NIST NCSTAR 1-9, WTC Investigation 574
"Once Column 79 buckled, the column section above Floor 14 began to descend downward. Column 79 began moving downward at the roof level approximately 0.2 s after Column 79 buckled and 0.6 s before Column 80 buckled."

As shown in the NIST Figure 12-45, column 79 at roof level, had a vertical displacement of
0.83 meters in 0.6 seconds (simulation timeframe 14.9 to 15.5 seconds), before the next column,
column 80 buckled.

So the NIST is hypothesizing that 0.2 seconds after it buckled, that column 79 was descending from floor 14
to the roof, with a descent velocity of 4.6 m/s2 or about ½ g.

Supposedly, in 1/5 of a second, for 30+ floors above the point of buckling, column 79 lateral supports from all the undamaged interconnections, were ripped free.

Amazing.

MM

 

[Oystein]

...
So the NIST is hypothesizing that 0.2 seconds after it buckled, that column 79 was descending from floor 14
to the roof, with a descent velocity of 4.6 m/s2 or about ½ g.

Supposedly, in 1/5 of a second, for 30+ floors above the point of buckling, column 79 lateral supports from all the undamaged interconnections, were ripped free.

Amazing.
...

Isn't it?

Now, apart from displaying incredulity, what did you mean to argue?

 

[Furcifer]

The kinetic energy available to do work (i.e. structural damage) generated by the thermal expansion is -T*ΔS_internal . In general, this quantity will be only a fraction of the heat influx ΔQ, as is typical of the efficiency of most heat engines. The literature (tribology, metallurgy, etc. often in the context of irreversible thermodynamics) has methods for calculating the internal entropy production.

The maximum possible damage, and therefore the best case scenario for the NIST’s explanation, is when work is treated reversibly. Then, the initial state S_i is the same as the final state S_f (remember, the “final state” being the conveniently chosen end point of the NIST’s phase 2 free fall portion, rather than the total collapsed state of the entire building). In this best case, we would expect to see no more energy than the amount -T*ΔS_internal appear at the output. In real processes, entropy can be added as it propagates, in which case -T*ΔS_internal becomes less negative, in other words less energy is available to do work. This agrees with our intuitive idea of energy dissipating due to friction as it propagates. If -T*ΔS_internal is absorbed by the potential energy of the building before it can do critical damage, then +T*ΔS_internal is transferred to the structure as heat, leaving ΔS_internal < 0 ; the building establishes a new equilibrium and remains stable.

Instead, at the output we see KE_{upper section} . In post # 252 we saw that even when the entire quantity of heat flux into the girder is available to do work, that amount of energy is still orders of magnitude less than KE_{upper section} . And given that the actual quantity that can do damage, -T*ΔS_internal , is only a fraction of the input heat, the disparity between the input and output energy is that much greater. This suggests that a massive amount of energy ΔE = -T_f*ΔS_additional had to have been added to perform the balance of work,

- T*ΔS_internal + ΔE = KE_{upper section} .​

Also, taking into account the relaxation times associated with doing work on materials, it’s unlikely that critical damage could have propagated across the entire building in less than a second, which would have been necessary in order to acheive the collapse’s observed high degree of symmetry.

Putting together posts #151, #215, #252, #333, we should be able to answer the question whether or not the official explanation for the collapse of WTC7 is consistent with the Second Law of Thermodynamics. A similar approach can attempt to answer the same question for the Twin Towers.

I suppose we should just ignore the change in chemical potential

I can't even begin to help correct this level of nonsense. Suffice to say nobody in their right mind would even attempt to determine the change in entropy of an entire building.

 

[triforcharity]

Your example would be fine if it allowed for the lateral bracing provided by all the intact floor systems.

MM

Wow, that is almost a ******* stundie!

LATERAL support does NOTHING when it comes to VERTICAL loads.

But hey, that is cool.