Merged Freefall is not evidence for Controlled Demolition

[ozeco41]

@ozeco
The contribution to motion of the rotating beam is an acceleration if all vectors are considered in cartesian units. If you observe a rotating beam (rotating in a vertical plane, axis of rotation parallel to the ground) from the ground, the vertical velocity vector will change from upward to zero then downward and through zero again. The definition of acceleration is a change in velocity.
Therefore if one is plotting vertical acceleration of a point that is influenced both by gravity and rotation those accelerations will be additive.

Understood - those were my starting points.

Remember that the purpose of my post #393 was to assist david.watts with comprehension of free body physics starting from where he was and advancing to applying it to the actual WTC7 collapse. So I deliberately avoided putting the full solution into the post.

And I was unsure of David's current level of comprehension given some confusion expressed in his requests.

So I started at base level using the rotating beam example. And warned that the rotating beam example is not as simple as it looks. I doubt that david.watts is ahead of me, other members may be. If they are that is great but the posted explanation wasn't for those members - and I wasn't risking leading David astray.

Hence my foreshadowing of three stages to get to the real WTC7 event - the first stage I posted to be followed by a more comprehensive one dimensional model - after that a 3D version since WTC7 collapse was essentially 3D and cannot be understood/explained in 1D.

If I am correct the "problem" with the rotating beam model is that there is an obvious and WRONG interpretation plus a more complex and correct one which is harder to comprehend.

Hence my several hints - if anyone sees the true situation and thinks my one step at a time is not warranted then post the explanation. But that does not solve my challenge to set a learning path for David - if in fact he needs it. His call when he "recovers" to make further comment.

Meanwhile the truism in your post is "The definition of acceleration is a change in velocity"

OK - we are trying to add rotational movement to vertical downward movement to show addition of acceleration.

Where does the added acceleration come from?

HINT -- I nearly fell for it myself - and I'm usually very confident with free body physics so it was a shock and I'm still not 100% sure.

It's a sad state when an engineer like me is unsure of physics....must be age.

 

[alienentity]

There have been several bona fide responses. Thank you.

ozeco41: “If the building is falling then all columns have failed.”
Yes, well said and I agree. I am not sure what the 10% of “esoteric possibilities” might be, but I am sure you have some in mind. It will be interesting to get to those should we get to that point. And, no doubt we will. (At least, if the internet remains alive and well.)

To Spanx: No, I don’t think it depends on “how” the structural supports gave way, just that they all did/must have given way -- in the scenario -- at the same/virtually the same/very nearly the same time.
Looks like Clayton would obviously agree.

jaydeehess, I was not familiar with verinage demolitions but I am now.
I contend that the technique obviously -- after watching a couple of videos -- results in all of the support giving way at the same time.
But, is that the only way? I think we all agree that is not the “only” way; and I do realize that is not what you are saying. Anyway, I am just trying to see if anyone agrees with what I presented in the scenario regarding any building and not how the loss of all support might have occurred.

Gone Fishin’, regarding the “tip” of a rotating beam moving faster than freefall: Yes, it makes sense to me that while free falling and rotating downward the tip would be moving downward at greater than free fall.
However, is not an additional (not just gravity ) force acting on the tip? Centrifugal force would be in play, would it not? Interestingly, when studying basic physics I seem to remember that centrifugal force is not an actual force, but only an apparent one. I’ll need to check that out; I may well be wrong.

I guess a better way to say it might be that two vectors apply and not just the free fall vector. The other being of course the ‘spinning,’ or ‘rotational,’ vector. (I don’t know what else to call it, but you know what I mean.) They would be added together to get “faster than free fall.” And of course, that same tip would be traveling slower than free fall when it is rotating upward. The vectors would be, in essence, opposite in direction.
……

I ask again basically the same question: Does anyone else either simply agree or not agree with the scenario? And if so, which is it?

(Actually, I’m not sure where to go from here. But I ought to go somewhere, don’t you think? Ah darn it...some -- hopefully not ALL -- of you may not think so.)

Regards.

I'm with LSSBB on this one. My general take - visualizing the damage to floor truss connectors described by NIST in their model, and the fact (or call it engineering consensus if you prefer) the collapse progressed E to W - is that essentially some of the mass of the building was accelerating generally downwards as interior columns failed. Some of the connections between those columns and the exterior columns were destroyed by the fires due to thermal expansion already. That process was far enough along by the time the exterior columns (and moment frame mentioned by LSSBB) were pulled inwards and down that you could see some acceleration above g.
It probably wasn't a long interval, but it wasn't instant or simultaneous.

To me that's the simplest mechanical generalization I can envision that fits exactly with the observed collapse.
If you think about it for a moment you can explain the acceleration by a simple thought experiment: attach two weights by a length of cord or wire; go to a place where you can set them both on a ledge above a substantial drop. Push one of the weights off and you can see the other weight will experience a sudden acceleration until it 'catches up' with the speed of the falling one. The amount of acceleration will depend on how long the first weight has been allowed to drop (and gain velocity) and the mass of the weights, etc..
But you could easily generate acceleration beyond 1g by that method.

That's my take on it anyway.

 

[jaydeehess]

With a truly free body rotating about its CoM, obviously something had to initiate the rotation.
In ozeco fashion let's leave that aside for now. Let's also not have it falling but rotating on a secured axis.

The end moving upward will have an upward acceleration, the opposite end will be accelerating downwards. The sum at any point in time, of all points of the beam will be zero. There is no NET force causing this rotational acceleration.
Now, if the beam drops in free fall the CoM falls at 'g' and the sum of acceleration of all points along the beam equals zero so the beam as a whole falls at only 'g'.

Big BUT, if all you are doing is measuring ONE point on the beam as itfalls you will measure the average velocity between time periods, due to gravitational effect + the vertical component of the rotational velocity. The later will change with time thus when you calculate average acceleration between time periods your resultant plot will show a changing acceleration. If the beam started out vertical that acceleration would increase to a maximum when the beam passed the horizontal, decrease to 'g' as it passed vertical, and, f allowed to keep going, decrease to a minimum that is less than g' as it again passed horizontal, . It would increase to 'g' at its vertical again, etc.

However, a point on WTC7 would not be truly free. It would likely at least begin rotation contrained at its lower end. It is also not going to be even visible by the time it is horizontal. The higher above the center of mass the more you will measure/ calculate an ever increasing acceleration.

This alone invalidates Chandlers conclusions.

Now, there is that niggleing matter of a pull by already moving previously collapsed portions of the structure.

 

[kid meatball]

I'm with LSSBB on this one. My general take - visualizing the damage to floor truss connectors described by NIST in their model, and the fact (or call it engineering consensus if you prefer) the collapse progressed E to W - is that essentially some of the mass of the building was accelerating generally downwards as interior columns failed. Some of the connections between those columns and the exterior columns were destroyed by the fires due to thermal expansion already. That process was far enough along by the time the exterior columns (and moment frame mentioned by LSSBB) were pulled inwards and down that you could see some acceleration above g.
It probably wasn't a long interval, but it wasn't instant or simultaneous.

To me that's the simplest mechanical generalization I can envision that fits exactly with the observed collapse.
If you think about it for a moment you can explain the acceleration by a simple thought experiment: attach two weights by a length of cord or wire; go to a place where you can set them both on a ledge above a substantial drop. Push one of the weights off and you can see the other weight will experience a sudden acceleration until it 'catches up' with the speed of the falling one. The amount of acceleration will depend on how long the first weight has been allowed to drop (and gain velocity) and the mass of the weights, etc..
But you could easily generate acceleration beyond 1g by that method.

That's my take on it anyway.

A really good roller coaster will show the same principle. The old wooden coaster at Vancouver's Playland has a huge first hill. Some say the front of the coaster is the best seat but I disagree. Sit in the back. After the front of the train crests the first hill it starts to accelerate down the drop while the farthest back cars accelerate up the remainder of the hill. The result is the back of the train kind of whips over the top of the hill. The cars at the front of the train experience a nice smooth acceleration while the cars at the back are subject to much more abrupt feeling changes in motion.

 

[LSSBB]

With a truly free body rotating about its CoM, obviously something had to initiate the rotation.
In ozeco fashion let's leave that aside for now. Let's also not have it falling but rotating on a secured axis.

The end moving upward will have an upward acceleration, the opposite end will be accelerating downwards. The sum at any point in time, of all points of the beam will be zero. There is no NET force causing this rotational acceleration.
Now, if the beam drops in free fall the CoM falls at 'g' and the sum of acceleration of all points along the beam equals zero so the beam as a whole falls at only 'g'.

Big BUT, if all you are doing is measuring ONE point on the beam as itfalls you will measure the average velocity between time periods, due to gravitational effect + the vertical component of the rotational velocity. The later will change with time thus when you calculate average acceleration between time periods your resultant plot will show a changing acceleration. If the beam started out vertical that acceleration would increase to a maximum when the beam passed the horizontal, decrease to 'g' as it passed vertical, and, f allowed to keep going, decrease to a minimum that is less than g' as it again passed horizontal, . It would increase to 'g' at its vertical again, etc.

However, a point on WTC7 would not be truly free. It would likely at least begin rotation contrained at its lower end. It is also not going to be even visible by the time it is horizontal. The higher above the center of mass the more you will measure/ calculate an ever increasing acceleration.

This alone invalidates Chandlers conclusions.

Now, there is that niggleing matter of a pull by already moving previously collapsed portions of the structure.

I'm not following you on this rotation thing. How are the forces being applied by rotational movement? The beams and girders attached to the exterior are actually pivoting downward as the interior columns collapse downard, since the exterior is fixed until the exterior columns finally give way. When the exterior we can see begins to fall, they do drop at the exterior end and start to rotate the other way, however I don't see them applying rotational force as much as downward force since the interior fall is still ahead of the interior and the weight of the interior is pulling the beams and girders downward. The forces stack up in the center-of-the-earth direction, applied force plus weight, with resisting force at the bottom acting in the opposite direction.

Alienentity's example is a good one, here is another:

Say pillar A is attached to another pillar B by a bunch of bars. Pillar B begins to collapse and fall. The bars attaching the two pillars go down at the B end, and a compressive force is applied to pillar A. Then pillar A breaks under the compressive force applied through the bars. Pillar A has it's center of gravity drop at g, however the compressive force is still being applied and adds to the force of gravity pulling down A. The force of gravity plus the compressive force minus the resistance to compression of A is the total force.

Once you have the forces stacked up, you divide out the mass of pillar A and you have it's acceleration. Nothing is preventing that acceleration from being over g, as long as sufficient force is being applied to counterbalance the resistance to compression.

 

[ozeco41]

With a truly free body rotating about its CoM, obviously something had to initiate the rotation.
In ozeco fashion let's leave that aside for now. Let's also not have it falling but rotating on a secured axis.

Agreed all three points.

Key points left full black - other points greyed out

...The end moving upward will have an upward acceleration, the opposite end will be accelerating downwards. The sum at any point in time, of all points of the beam will be zero. There is no NET force causing this rotational acceleration.

Yes...but those identified accelerations are conflating the two explanations subject of the warning I gave. (Both greyed points agreed)

Now, if the beam drops in free fall the CoM falls at 'g' and the sum of acceleration of all points along the beam equals zero so the beam as a whole falls at only 'g'.

Agreed

Big BUT, if all you are doing is measuring ONE point on the beam as itfalls you will measure the average velocity between time periods, due to gravitational effect + the vertical component of the rotational velocity. The later will change with time thus when you calculate average acceleration between time periods your resultant plot will show a changing acceleration.

Yes.

If the beam started out vertical that acceleration would increase to a maximum when the beam passed the horizontal, decrease to 'g' as it passed vertical, and, f allowed to keep going, decrease to a minimum that is less than g' as it again passed horizontal, . It would increase to 'g' at its vertical again, etc.

Are you sure. Drinks on me if I'm wrong.

As the rotating tip moves from vertical top down to descending horizontal point the downwards velocity vector increases from zero at top to equal the rotational perimeter velocity as it passes horizontal.

That is the velocity variation. Down velocity is increasing all the way from top to horizontal half way point THEN decreasing from half way/horizontal down to bottom.

And at the horizontal point the velocity is not changing. So acceleration due to rotation is zero at that point. Vertically downwards acceleration has increased for zero at the top through a maximum then reduced back to zero.

If that is right - see what I mean about it not being obvious.

If it is wrong - drinks on me. Next time you are in Sydney

...However, a point on WTC7 would not be truly free. It would likely at least begin rotation contrained at its lower end. It is also not going to be even visible by the time it is horizontal. The higher above the center of mass the more you will measure/ calculate an ever increasing acceleration...
Now, there is that niggleing matter of a pull by already moving previously collapsed portions of the structure.

Since I am trying to respond to david.watts scenario which was specifically NOT WTC7 on 9/11 I don't want to discuss the actual WTC7 side track at this time.

This alone invalidates Chandlers conclusions.

Yes - but I'm not discussing Chandler

 

[jaydeehess]

Gotta jet. Will post on the morrow re: queries.

 

[LSSBB]

Gotta jet. Will post on the morrow re: queries.

When you do, draw us a picture. It's worth a thousand words, you know.

 

[ozeco41]

Gotta jet. Will post on the morrow re: queries.

No problem other than the two separate topics confusions.

Since I was trying to answer d.w's question we can go to PM that would free me up to engage in the ongoing WTC7 specifics stuff - without confusing myself and everyone else.

I don't want to abandon d.w BUT so far no response due to his "social activities" - if he isn't interested I'll drop the while thing.

 

[ozeco41]

I'm not following you on this rotation thing.

JDH was responding to my comments which in turn were directed at david.watts question at post #365 which was not specific to WTC7.

If a building -- WTC7 or any other -- is observed to collapse on all sides

...so specifically not WTC in the actual 9/11 collapse.

So JDH and I are not discussing WTC actual mechanism but a falling rotating beam model

That model was put to david.watts by 16.5 at post #382.

It was a good starting point to walk d.w through the free body stuff working up to the full 3D complexity of WTC7 and the North Façade "over g" issue.

So two current topics getting a bit confused.

 

[brazenlilraisin]

I'm not discussing Chandler

Can't everything Chandler ever said or ever says about 9/11 be summarily dismissed on the basis of "thermite rockets" alone?

 

[jaydeehess]

Hmmm, a free drink next time I am in Sydney. Sounds good but given my personal finances and situation, your wallet is safe.

Yes, velocity in the vertical changes in a rotating beam. Beginning with beam vertical, measuring point at top, vertical velocity component rises as the point rotates down, from zero to max at horizontal. It continues to be a downward vector but decreases to zero again as it passes bottom vertical. Then reverses direction(moving upwards now), etc.

Now, as LSSBB asked, how does this apply to WTC7? Once the exterior began collapsing , the beams connecting the exterior to the already collapsing interior are applying not only a downward force on exterior columns, but also a horizontal component to the south. Those beams have not all swung completely to vertical so the pull they are applying is a diagonal, and can be expressed as vertical and horizontal components.

Thus the exterior is both falling under gravity and rotating( top to the south) , in addition, the NIST Sim shows the lower end of the exterior, at approx 8th floor , to be moving north. Measuring the vertical velocity of a point at the top of the exterior will include the velocity due to falling under gravity, the velocity due to the vertical component due to the pull of interior collapsed , and the vertical velocity component due to the rotation of the exterior.

Sorry no pic. I haven't figured out how to create one on the tablet. If I get time on my desktop I could at least create one in Paint. Call it MSPaintSim

 

[jaydeehess]

Can't everything Chandler ever said or ever says about 9/11 be summarily dismissed on the basis of "thermite rockets" alone?

Well, when you put it that way......

 

[david.watts]

Back again

Sorry that I have not been quicker to the topic at hand. After all, it 'twas I that initiated it; the current version at least. And while saying that I initiated this, I do understand that this discussion/topic was merged with a prior one. As to not responding more quickly, I have simply been tied up as many things have come my way in just the last couple of days.

There have been many posts since I last left one two days or so ago. Many good points have been made. Among those points are things like the nature/physics of 'rotating beams,’ ‘faster than free fall,’ and relating my question -- which I did not intend to be related to WTC7 -- to WTC7. Of course that is what this is obviously about. But I was simply trying to see if we could find a starting point where if not all of us, at least most of us could agree . For if, in my opinion, we cannot agree on something that is seemingly very simple and straight forward, we’ll have trouble agreeing on anything.

Again, my scenario:
If a building -- WTC7 or any other -- is observed to collapse on all sides at the same/virtually the same/very nearly the same time, would that not mean that all of the structural support must have given way at the same/virtually the same/very nearly the same time?

As to: “at the same/virtually the same/very nearly the same time” I obviously was not trying to be absolutely precise. The reason being,
we could all observe the collapse of some generic building ‘x’ -- not building 7 -- and not agree precisely on whether or not it was instant or things happened over a period of .5s or 1s or some other very short time frame. But we should be able to agree, in my hypothetical scenario, that whatever it was that happened, it happened very quickly.

And the basic premise being that if an entire generic building ‘x’ -- all four walls and roof and roofline -- began falling “all at once,” whatever was supporting the entire building -- all four walls and roof and roofline -- must have given way “all at once.”

Stated this way, can we agree that this must be the case as to the hypothetical collapse of generic building ‘x.’? I cannot come up with any other possible explanation; at least any reasonable one. If any of you can, fill me in.

I will try to be more prompt with my responses. This has been interesting seeing the many different thoughts, ideas, and postulations.

 

[jaydeehess]

Sure, absent any other contribution to vertical motion, a structure observed to accelerate downward at 'g' would have no columnar support.

Basically its no different than a free body fall.


,,,and I will restrain myself from comparing such a scenario to any specific real event.

 

[DGM]

Stated this way, can we agree that this must be the case as to the hypothetical collapse of generic building ‘x.’? I cannot come up with any other possible explanation; at least any reasonable one. If any of you can, fill me in.

Sure but, what does this have to do with the argument that free-fall means CD.

It certainly has nothing to do with the case of 9/11. This sounds like trying to work backwards from nothing to make something.

Why bother with this "hypothetical"?

 

[beachnut]

... Again, my scenario:
If a building -- WTC7 or any other -- is observed to collapse on all sides at the same/virtually the same/very nearly the same time, would that not mean that all of the structural support must have given way at the same/virtually the same/very nearly the same time? ...

Why do 911 truthers make up scenarios? Is it to back in CD by getting agreement. Does the sun rise in the morning? yes, see, 911 was an inside job...

Nope. It makes no sense to make up a scenario which did not happen on 911. WTC 7 collapse started internally, and the evidence is the Penthouse falling into WTC 7 seconds before parts of the facade slowly start to fall at less than g. Less than g. If the supports were all gone in your scenario, WTC 7 collapse would start at an acceleration equal to g. oops

Is this an attempt to back in CD? Get people to agree, then confirm the CD fantasy?

WTC 7 burned all day and the structural support was compromised by the fire. If WTC 7 had stood after the fire, it would be dismantled due to damage from fire; totaled by fire before it collapsed.

Another pilot, Jumbo pilot at that, I was a Heavy pilot by definition. Do you have a type Rating in the 747? Why not?

Believing in CD is like flying an instrument approach to the runway of truth, but you are looking at the wrong airport, short of your destination off to the side of woo, you can see the bright lights and it looks better than the ILS you letting get off course with the Runway of truth at the end (where reality and real evidence wait to cure the lies, cure the illusion of CD CTs). You fail to fight the illusion, and landed at WOO, the international airport of lies and conspiracy theories based on nonsense. The land of no evidence, zero logic, and a lack of science.

Not sure if your pilot training covered illusions. In the USAF we spent hours on physiological training, from hypoxia to illusions. We were trained to fight th illusions, beware of them. Where is that training to avoid being fooled by the lies of 911 truth. I use my training in college, engineering and flying to help me see false statements - I look it up myself for hours using independent sources. I hate it when 911 truthers think I support some official story, when they have no idea how I came to understand 911, and why I can see 911 truth is BS, lies, and fantasy.

911 truth claims are made up by humans and they sound good to some people. Humans have a habit of saying things that sound right to other humans, and they spread lies, and other believe them without thinking. 911 truth has no valid claims, all 911 truth claims are lies; not sure why some people fail to think for themselves. Why do things humans make up sound good to other humans? They have a pattern which must be pleasant to some, for some unknown reason. Can't imagine who the slogan of "broke the laws of physics" makes sense to, because it is pure stupid.


I know where you stand? Not exactly. Not sure why 911 truthers are unable to clearly state their conclusions. If I knew 911 was the big inside job of CD I would prove it in less than a year and team with a news paper to share in the Pulitzer. What has 911 truth done? Nothing.

Yes, if you take 2 apple pies plus 2 pecan pies, you can smart off with pi. Maybe that is how I got my special seat in high school chemistry.

911 truthers seem upset they are stuck with a conspiracy theory, so silly it defies reality. 19 murderers did 911, a simple plot which used our culture and customs against us. 911 truthers think conspiracy theorists get a bad rap. 19 did 911, not a theory a fact, it was a conspiracy, not a theory.
The collapse of WTC 7 was due to a fire, a fact. 911 truth has a theory of CD which does not fit. 911 truth is confused at best, WTC 7 looked like a gravity collapse, and CDs look like a gravity collapse. Most the energy used to destroy buildings in CD is from E=mgh. Gravity is g, h is the height, and m the mass of the building - is this a model 911 truth can grasp? If not they don't do science, they do woo. I am an engineer and a pilot, and trained in aircraft accident investigation, and have been accident science commander after the fire rescue handed the site to the board, to board president on investigations - yet, any layperson can see CD and 911 truth are full of BS, no evidence, and unable to back up anything with logic and knowledge.

CTists are not nuts, their ideas are.

Why can I dismiss 911 truth claims? Because I take the time to dig into the facts. When Balsamo and his idiot pilot followers say impossible maneuvers by Hani. I got the FDR and went though line by line. I got the NTAP data, RADAR data and went though point by point. I matched RADAR to FDR. What did I find. Poor flying and not a single difficult maneuver. Line by line, and 911 truth lied, big time. I spent much more time investigating, the the few seconds some nuts did making up the lie of the impossible/difficult maneuvers. Most 911 truth claims are so dirt dumb stupid, they fail at face value - and most intelligent lay people can debunk 911 truth by reading the claim. Why can't you?

I have flown from 60 south to 60 north, Norway to Perth, Diego Garcia to Japan, Guam, and Saudi Arabia; love to fly, love my seat up front. And I loved working as an engineer with human factor experts at Wright Labs - I see 911 truth as one of the most anti-intellectual movements ever. My flying training taught me big time to use logic, sound judgment and knowledge to make rational decisions - stop - think - collect your wits - but first and foremost fly the jet. 911 truth claims are not rational, and have no support. CD is a lie made up by conspiracy theorist who have no evidence.

 

[Richard the G]

Again, my scenario:
If a building -- WTC7 or any other -- is observed to collapse on all sides at the same/virtually the same/very nearly the same time, would that not mean that all of the structural support must have given way at the same/virtually the same/very nearly the same time?[/I]

Yes and no.

It does mean that the structural system is offering almost zero effective resistance.

Let me ask this by way of a demonstration. What makes a concrete chimney collapse vertically, at nearly freefall speed, rather than fall over? Its easy: when concrete is overloaded in compression there is an explosive failure ( no explosives). The amount of time it takes the concrete to reach its failure load is milliseconds, at which point the next failure occurs. So it appears that the concrete below offers no resistance, but it does, its just not significant.

Similar thing happens when a 15 story wall, drops on a beam to column connection below. It slices through it in a millisecond, and then what happens when 16 stories of floor...etc etc

The (no explosives) are in case you are a truther as they tend not to understand. What do you think?

 

[david.watts]

"Why bother with this "hypothetical"?

I posted: "If a building -- WTC7 or any other -- is observed to collapse on all sides at the same/virtually the same/very nearly the same time, would that not mean that all of the structural support must have given way at the same/virtually the same/very nearly the same time?"

There were two, maybe three replies that agreed. That surprised me. I thought if we can't agree here, most likely we ain't gonna agree anywhere on this topic. But, I was wrong; I realize now that I should not have used, "If a building -- WTC7 or any other --." I could have avoided some of the different directions the discussion took. I wish that I
had put it the same way as I did the 2nd time around: 'hypothetical collapse of generic building 'x'.' Unambiguous.

So, I posted the hypothetical so that we can all use it as a starting point; if, of course, we agree on the premise. Where it goes from here(?) ... well, it probably will end up right back from where we began. But, if we can keep it to one element at a time, at least I will have a better idea where we diverge and hopefully we all will -- if you care. All of you -- with a couple of exceptions -- start from, "it was not a CD." Fair enough. But, while agreeing 'not a CD,' it seems that there are a number of different ideas about how things commenced and progressed and whatever else, i.e., you are not all in agreement about just exactly what happened. That is, are there not different (non-conspiratorial) theories amongst the people here as to the collapse of building 7? I know this subject has been beat up to no end, but it would be interesting to see where all of you agree or disagree. Perhaps there has been a thread discussing this. If you know of one, point me there.

 

[ozeco41]

..."Why bother with this "hypothetical"?

Simple. You are seeking to understand some issues about collapse. You want to start from basics THEN progress to applying principles to explain the actual WTC7 collapse.

I have suggested that it needs 3 or 4 stages and have pasted comments to explain your hypothetical as stage 1. I have added in the rotating beam example as the next step towards stage 2.

Other members are ignoring your hypothetical and going straight to the actual collapse. Whether or not that helps your understanding. If you and I are on the same track we can either deal with it here - ignoring the other topics OR take it to PM OR start another thread.

If I have misunderstood you - ignore the rest of my post and discuss the real collapse with the other members. Otherwise read on.

The problem with another thread is that the answers to what you are asking go along way to addressing the OP - as an issue of principle rather than the WC7 specific stuff...

However (if you are still with me ) my responses to your next points:

....relating my question -- which I did not intend to be related to WTC7 -- to WTC7. Of course that is what this is obviously about. But I was simply trying to see if we could find a starting point where if not all of us, at least most of us could agree . For if, in my opinion, we cannot agree on something that is seemingly very simple and straight forward, we’ll have trouble agreeing on anything...

I have been crystal clear what your question was from my first responses (posts #366, #388, #393).

So this is where you and I can agree:

...Again, my scenario:
If a building -- WTC7 or any other -- is observed to collapse on all sides at the same/virtually the same/very nearly the same time, would that not mean that all of the structural support must have given way at the same/virtually the same/very nearly the same time?

Agreed that was your question AND you are correct provided we sort out what you mean by the timing definition. AND I understand what sort of vagaries you are trying to allow for.

...As to: “at the same/virtually the same/very nearly the same time” I obviously was not trying to be absolutely precise. The reason being, we could all observe the collapse of some generic building ‘x’ -- not building 7 -- and not agree precisely on whether or not it was instant or things happened over a period of .5s or 1s or some other very short time frame. But we should be able to agree, in my hypothetical scenario, that whatever it was that happened, it happened very quickly.

Also understood and agreed. If the timing definition needs more clarity we can deal with it when the situation arises. Hence my earlier comment about 90% - I was trying to allow for the same issues you are concerned about WITHOUT stopping discussion leading towards agreement.

(Or trying to force you back onto "actual WTC7" collapse. )

....And the basic premise being that if an entire generic building ‘x’ -- all four walls and roof and roofline -- began falling “all at once,” whatever was supporting the entire building -- all four walls and roof and roofline -- must have given way “all at once.”

Yes - we can discuss what "all at once" means in any specific situation if we need to.

...Stated this way, can we agree that this must be the case as to the hypothetical collapse of generic building ‘x.’? I cannot come up with any other possible explanation; at least any reasonable one. If any of you can, fill me in.

I agree but you may find that some members are reluctant to agree with simple "must be true" statements and/or utilise such simple realities within the setting of an argument....we have had several threads over the past 2-3 years drag on whilst nit pick details were argued as a consequence of some simple facts being ignored. (Tilt v axial contact and "Missing Jolt" being two if you are aware of the topics PLUS T Szamboti derailing the thread about his own paper so he didn't have to defend it.)

However all those matters are a derail for now so leave them aside. PM if you want clarification without derailing the thread further.

....I will try to be more prompt with my responses. This has been interesting seeing the many different thoughts, ideas, and postulations.

Take your time.

I see you have posted again - and it loks like you and i are on the same track.

I wont edit this to match your latest - look out for further comment later today.