double post

Originally posted by Akareyon
I absolutely agree with you. That's exactly what I'm trying to say. Please take Fig. 3 and a ruler and draw a new line for m*g. Attention! This is a different g, not the 0.6g you're referring to but the g we have to derive from the very first equation to calculate K from P_dyn from Eq. (1) in Bazant/Zhou, 2002 using the 0.6*g you mention.

Why how do you want to calculated K from P_dyn? That doesn't really make sense to me. (assuming K = kinetic energy). As long as there is acceleration kinetic energy increases. So the kinetic energy available at the subsequent floor is higher than the energy available at the floor before.

Great thread so far and very interesting discussion.

Glad to see the discussion is mostly quite civil

Thanks to both Akareyon and IronWristWatch for enlightening comments without the usual name-calling. I'm looking forward to more quality posts from both of you.

Let's not fill this thread with the usual rubbishing.

Thank you, Doctor.

Not much time at the moment. Will get back to this shortly.

Originally posted by -PLB-
As long as there is acceleration kinetic energy increases.

Yes, as long as there is acceleration. Remember: buildings and structures are made to decelerate earth's acceleration to v=0, storing potential energy, keeping it from getting kinetic.

Originally posted by Akareyon

Originally posted by -PLB-
As long as there is acceleration kinetic energy increases.

Yes, as long as there is acceleration. Remember: buildings and structures are made to decelerate earth's acceleration to v=0, storing potential energy, keeping it from getting kinetic.

What is stopping acceleration, though? The building's vertical supports have no way of focusing the weight of the building once the collapse has begun. Potential has become Kinetic already, and momentum is gathered. Acceleration will increase automatically.

Originally posted by Varemia
The building's vertical supports have no way of focusing the weight of the building once the collapse has begun. Potential has become Kinetic already, and momentum is gathered. Acceleration will increase automatically.

Will it?

Earth's acceleration itself will not increase, it is ~9.81m/s².

Even if you throw a stone from the highest mountain, air resistance will decelerate it. Of course, earth's acceleration is much greater than the deceleration, so both soon find an equilibrium which results in what I think is called "terminal velocity". The stone won't go any faster anymore unless with a rocket rucksack. And if that is used up, the stone will slow back to terminal velocity!

Only in a vacuum will acceleration constantly increase velocity. In vacuum, a small feather and a diesel engine, if dropped from the same height, will touch ground simultaneously because there is no air molecules in the way that must be accelerated out of the way - which results in deceleration - so no terminal velocity is reached.

If you throw the stone into the water, earth's will still be 9.81m/s². The resisting forces of the fluid will decelerate the stone until it reaches terminal velocity and it gracefully sinks down to the ground at constant speed. In water, there are more and denser molecules which the stone has to accelerate out of its way, resulting in even more deceleration, hence, deceleration and acceleration find their equilibrium even sooner, terminal velocity will be slower than if falling through the air.

The towers also reached terminal velocity as earth's acceleration and the deceleration of the lower structure found an equilibrium.

The question that no expert and no layman could answer in the last ten years is why the solid structure (not a gas, not a fluid, a solid structure) that has decelerated the upper block for over 30 years, suddenly and gradually switched to decelerating the fall with just half of its original deceleration in less than 20 seconds.

Did the solid become a liquid?

I wish to stress this: the experts don't know, they don't have the slightest clue, the explanations they have brought forward are self-contradictory. So I have a personal issue with fellow laymen and media and officials telling us that this is "normal" and "inevitable" and "the way it should be" when in fact each and every real-world or thought model requires a) work to be done or b) a deliberate and inventive effort to be made to bring a structure down.

I have an even greater issue with people telling me that models just aren't complex enough, that the towers were just too big and too heavy, that you need to be an expert to make an educated judgement. I don't believe experts, I put my trust in that which I can falsify or verify through personal experience, and I would like to invite you to do the same. Please, become an expert, become a scientist, become a politician, become an economist on matters that have an impact on you.

I know this rant doesn't have much to do with the Bazant paper anymore, but this is the start of my wanderings that led me here. My very first memories I have of my time in this world have to do with my wondering what is going so wrong, and now I understand and this topic is just an example for what is going on.

I am sick of people repeating what they've been spoonfed by authorities, they are like proselytes, perpetuating what they don't understand, assisting the effort of a selected few who invented the deception and impeding the progress of those who strive to use their knowledge to make this world a better and more peaceful place. I have found that pattern in the media, in education, in psychology, economics and politics but I was careful to meddle in these affairs because I am no expert (two experts = three opinions), and it is so easy to be called "insane" these days just for asking a question.

Since 9/11/01, the "inevitability" of catastrophic and global system failures even gained ground in physics, again those who demand constitutional analysis must expect diffamation. And again experts throw around with computer models and equations as they do when you ask why people elsewhere are starving while we throw our food in the dustbin, why war is peace, why freedom is slavery, why ignorance is strength, why truth is bunk and again we are supposed to trust them. Enough is enough. Next thing that happens is that they make us admit, as in Orwell's 1984, that 2+2 can be 3 or 5 sometimes ("or all at once"), depending on what's best for the party at the moment.

They are wrong, and they know it and they have a hard time to distract us from that. Don't outsource your own critical thinking. If you believe that 2+2=4, say so and let noone prove you otherwise. That's Orwell's definition for freedom. And if you believe that 2+2=5, that's fine as well, but then we have to find something different, more basic to agree on to start building our model.

Originally posted by Akareyon
The question that no expert and no layman could answer in the last ten years is why the solid structure (not a gas, not a fluid, a solid structure) that has decelerated the upper block for over 30 years, suddenly and gradually switched to decelerating the fall with just half of its original deceleration in less than 20 seconds.

Did the solid become a liquid?

The answer isn't that hard actually. A simple analogy would be thin ice. When you carefully walk on it, it will hold your weight. When you jump on it, it will break and you will fall through it.

Of course this is only an analogy to the phenomena where something that can hold a weight for years can fail in a matter of seconds when that same weight is dropped on it.

Originally posted by -PLB-
The supports of a building are not designed to decelerate a mass in motion, the supports are designed to counter gravitational acceleration of a stationary mass, plus some dynamic loading.

True.

[...] and as a result inevitable failed.

You say that with the voice of someone who is very sure that this is so, but you have nothing to back up this argument except the behaviour of WTC 1&2 and the experts who, in their papers, are repeating this mantra again and again and again. "After that, failure was inevitable", "The towers were doomed", "the structure was overwhelmed", while I can think of a hundred ways to stack things on top of each other that don't exhibit anything closely similar to the behaviour of the Twin Towers. Even worse, we must invent a mechanism to simulate the collapse, and in 10 years no inventor stepped forward to show what happened!

Of course the towers failed under the stress, so all these models don't apply, but you're missing the point: WHY?

Nothing else you or I or anyone has ever seen behaves this way unless is was made to do so, so please don't pretend to understand. You don't, Bazant doesn't, Greening doesn't, Jones doesn't, I don't. We're speculating. We don't know. Let's find out. That's what science and knowledge is about: not accepting things as "inevitable" and "self-explanatory". It was a phenomenon. It was unique.

Was there a self-destruct feature built into the towers by accident? Maybe, I'll give IWW's argumentation the benefit of the doubt. But please don't try to persuade me that the crumblification was the most natural thing to expect or even "inevitable".

//edit:

Of course this is only an analogy to the phenomena where something that can hold a weight for years can fail in a matter of seconds when that same weight is dropped on it.

The ice and the chain are good and valuable analogies, if we can translate it to the WTC model.

Originally posted by Akareyon
You say that with the voice of someone who is very sure that this is so, but you have nothing to back up this argument except the behaviour of WTC 1&2 and the experts who, in their papers, are repeating this mantra again and again and again. "After that, failure was inevitable", "The towers were doomed", "the structure was overwhelmed", while I can think of a hundred ways to stack things on top of each other that don't exhibit anything closely similar to the behaviour of the Twin Towers. Even worse, we must invent a mechanism to simulate the collapse, and in 10 years no inventor stepped forward to show what happened!

This isn't just conjecture. It is backed up by the known load capacity of the floors, and we know for 100% certain that this load capacity was not enough to hold the mass of the complete top section consisting of at least 12 floors. This is not opinion, but hard scientific fact, anyone can verify this.

Of course the towers failed under the stress, so all these models don't apply, but you're missing the point: WHY?

Nothing else you or I or anyone has ever seen behaves this way unless is was made to do so, so please don't pretend to understand. You don't, Bazant doesn't, Greening doesn't, Jones doesn't, I don't. We're speculating. We don't know. Let's find out. That's what science and knowledge is about: not accepting things as "inevitable" and "self-explanatory". It was a phenomenon. It was unique.

Where did you get the idea that this behavior is unique? I already suggested to look into Verinage demolition, which actually utilizes this behavior in order to take down buildings.

Was there a self-destruct feature built into the towers by accident? Maybe, I'll give IWW's argumentation the benefit of the doubt. But please don't try to persuade me that the crumblification was the most natural thing to expect or even "inevitable".

It was not a self-destruction. It was a destruction as a result of airliners crashing into those buildings and the subsequent fires. For WTC7 is was a result of only the fires. You could consider that as a self-destruction. But then you should agree that any wooden building has a self-destruct feature built in.

Originally posted by -PLB-
This isn't just conjecture. It is backed up by the known load capacity of the floors, and we know for 100% certain that this load capacity was not enough to hold the mass of the complete top section consisting of at least 12 floors. This is not opinion, but hard scientific fact, anyone can verify this.

The load capacity was not enough to hold the mass of the complete top section? So indeed it was hanging from a chain! I should have noticed that.

Where did you get the idea that this behavior is unique? I already suggested to look into Verinage demolition, which actually utilizes this behavior in order to take down buildings.

Indeed, in order to take down buildings. Were the towers built to be taken down by a fraction of their own mass?

It was not a self-destruction. It was a destruction as a result of airliners crashing into those buildings and the subsequent fires. For WTC7 is was a result of only the fires. You could consider that as a self-destruction. But then you should agree that any wooden building has a self-destruct feature built in.

Any wooden building I know of takes hours, not seconds, to turn to dust, ashes and rubble, if set on fire. Do you suggest we return to use wood for our buildings as a safety measure so we have enough time to bring the fire fighters in?

With all due respect, but this discussion is leading nowhere and we'll find no common ground to start from as long as you insist that the collapse was "normal" for the WTC if it isn't for any other known structure that was built not to collapse. It must be made to collapse. Does a plane suffice? Obviously not, because both towers survived the impacts, so something else must have triggered the mechanism. Was it the kerosene? Obviously not, because it burned off in around 20 minutes, as NIST claims. Was it the office fires, and if so, how come they triggered collapse this time when earlier office fires were not able to bring the towers down and other buildings didn't collapse either when they were burning like torches for several hours?

See the difference? I ask, you pretend to know better. That makes you an expert and me an idiot. There's something seriously wrong with our debate.

Originally posted by Akareyon
The load capacity was not enough to hold the mass of the complete top section? So indeed it was hanging from a chain! I should have noticed that.

Before the top section started falling, it was supported by the columns.

Do you agree that the floors would not be able to hold the top section? And if so, what do you think would hold it?

Indeed, in order to take down buildings. Were the towers built to be taken down by a fraction of their own mass?

I think we can safely assume that the intention of the hijackers also was to take down those buildings. Of course buildings are not build to be taken down by a fraction of their own mass. It is however possible with about any type of building.

Any wooden building I know of takes hours, not seconds, to turn to dust, ashes and rubble, if set on fire. Do you suggest we return to use wood for our buildings as a safety measure so we have enough time to bring the fire fighters in?

For WTC7 it took about 8 hours. For the towers it took a plane impact and at least one hour. I am not sure what point you are trying to make. I only brought up wooden buildings as example of something with build in self destruct system, according to your definition of it. I could as well have said that a car has a build in self destruct system.

With all due respect, but this discussion is leading nowhere and we'll find no common ground to start from as long as you insist that the collapse was "normal" for the WTC if it isn't for any other known structure that was built not to collapse. It must be made to collapse. Does a plane suffice? Obviously not, because both towers survived the impacts, so something else must have triggered the mechanism. Was it the kerosene? Obviously not, because it burned off in around 20 minutes, as NIST claims. Was it the office fires, and if so, how come they triggered collapse this time when earlier office fires were not able to bring the towers down and other buildings didn't collapse either when they were burning like torches for several hours?

I think it is just going in a direction you do not really like, a direction other than your preconceived opinion. Again, I point you to Verinage demolition. It is a clear demonstration that the phenomena of gravity driven progressive collapse is indeed "normal".

I see you are changing the subject to the collapse initiation. That is fine by me. But just for the record, do you acknowledge that gravity driven progressive collapse is possible?

See the difference? I ask, you pretend to know better. That makes you an expert and me an idiot. There's something seriously wrong with our debate.

Wouldn't it be healthier for the discussion to just point out where I am wrong rather than to come with this kind of reply?

Originally posted by -PLB-
I think it is just going in a direction you do not really like [...] Wouldn't it be healthier for the discussion to just point out where I am wrong rather than to come with this kind of reply?

That is right, I don't like the way this starts to become an argument for the sake of an argument. As I said, our discussion will lead nowhere as long as you insist on trying to persuade me or to feel like the winner of a fight at the end. You already have won. I surrender. No sarcasm here, I mean it.

See, I am not trying to prove you wrong.

However, I can't help but notice your reluctance to explain - in layman's terms - how and why the Twin Towers were in one second standing there like they did for three decades, just with small holes and a lot of fire in them, and less than twenty seconds later they were gone in a cloud of dust and a small heap of debris and why anyone on this beautiful planet should shrug their shoulders as if that is something that happens twice every day because it doesn't unless somebody puts a lot of work and planning into it, as also is the case with a vérinage because if you're not careful, the collapse won't look half as beautiful - more like one of those many incomplete keva plank and citibloc and jenga and domino destructions that can be found on YouTube where more often than not parts of the structure survive (ask me again if I believe in gravity-driven collapses).

I think we can safely assume that the intention of the hijackers also was to take down those buildings.

Of course the intention of the terrorists was to take them down - and what a success it was! Such a little input, such a huge outcome.

Of course buildings are not build to be taken down by a fraction of their own mass. It is however possible with about any type of building.

Before we start to turn in circles and I'm accused of dodging the subject again: please explain under which circumstances a building can be taken down by a fraction of its own mass.

Originally posted by Akareyon
However, I can't help but notice your reluctance to explain - in layman's terms - how and why the Twin Towers were in one second standing there like they did for three decades, just with small holes and a lot of fire in them, and less than twenty seconds later they were gone in a cloud of dust and a small heap of debris and why anyone on this beautiful planet should shrug their shoulders as if that is something that happens twice every day because it doesn't unless somebody puts a lot of work and planning into it, as also is the case with a vérinage because if you're not careful, the collapse won't look half as beautiful - more like one of those many incomplete keva plank and citibloc and jenga and domino destructions that can be found on YouTube where more often than not parts of the structure survive (ask me again if I believe in gravity-driven collapses).

I have tried explaining it, for example with the analogy with the ice, but it seems to me you ignored that (or maybe you just missed it). Why exactly do you think that analogy is wrong?

What kind of explanation exactly do you expect? What part of the collapse do you want to have explained? Initiation? The collapse itself? Or both? Can you pinpoint what exactly the issue is you have?

Just to be clear, I am in no way trying to "win". I am not really sure why you are bringing this up, it seems to me that my replies are all to the point an on the subject.

Of course the intention of the terrorists was to take them down - and what a success it was! Such a little input, such a huge outcome. Before we start to turn in circles and I'm accused of dodging the subject again: please explain under which circumstances a building can be taken down by a fraction of its own mass.

A very obvious example is controlled demolition using explosives.