Outside energy had to be introduced for the twin towers to collapse the way they did

reply to post by waypastvne


are you going to show me another tower that collapsed like the wtc towers did? oh, you can't? guess that means you're wrong

newton's third law applies the same to compression and shear. care to explain how it doesn't?

reply to post by Bob Sholtz


David Chandler said that WTC 1&2 collapsed at 65% of free fall acceleration. You didn't get the memo ?

That video maps the natural pressure wave inside of the building, pushing a head of the collapse front.

Originally posted by Bob Sholtz

newton's third law applies the same to compression and shear. care to explain how it doesn't?

Shear happens faster than compression = faster collapse.

Are you going to show me any photos of exterior columns between the spandrel plates ?

reply to post by waypastvne

WTC 1&2 failed under shear.

Then why don't you set up an experiment to demonstrated that a MULTI-ITERATION shearing sequence will behave as you describe.

Come on, it should be a simple matter if it is so obvious to you. I will await your video record of the experiment you did. I think you will find it is not so easy a trick to pull off in 3-dimensional reality as it is in the 1-dimensional image your head.




Just on a point of order here:

It isn't actually the mass OR the velocity that is the main decider, it is the average density. The reason I say that is that the single biggest factor in the whole thing is the coefficient of restitution (CoR). In other words, I am assuming that the more dense something becomes the more the CoR tends towards 1.

If the case was perfectly elastic, then the plane would "bounce off the building", imparting a negligible amount of damage. To the extent that it is frangible it has a far lower CoR though, so it does damage the tower and does destroy things, but as it does so it becomes more and more compressed, making it more and more likely to simply "bounce off" rather actually do any damage.

OS'ers, please the the section "Perfectly inelastic collision" here:
en.wikipedia.org... to see why the upper mass must slow down when it imparts force to the lower.

The impact force cannot be derived here because the question we are asking would make ANY derivation of that force circular.

Now return here:
en.wikipedia.org...
and see this:

Compare:


Can you see that as each collision occurs under a perfectly elastic event the upper floor would simply be stopped dead in its tracks.

But if the collision WAS perfectly elastic the completely collapse WOULD be assured, this is certain. BUT if you want shearing to occur, concrete to be smashed, steel beam to be dismembered etc. etc. etc. a perfectly elastic collision could not be occurring.

The only way something that looks exactly like a elastic condition could be observed is if the CoR was high, if the CoR was high the observed velocities could not be obtained, but if the CoR was low the damage could not be done.

See the problem?

Review this to see why it is neither mass, nor velocity, nor shear, nor compression nor anything else but the CoR that is the true mediator in this matter for anything beyond a grossly over-simplified single step model.


Just to be clear, the bullet is making its way through the water by SHEAR, not compression.

If you are imagining a simplified 1-d model with only one step you are deluding yourself.

Originally posted by Darkwing01


Then why don't you set up an experiment to demonstrated that a MULTI-ITERATION shearing sequence will behave as you describe.

Come on, it should be a simple matter if it is so obvious to you. I will await your video record of the experiment you did. I think you will find it is not so easy a trick to pull off in 3-dimensional reality as it is in the 1-dimensional image your head.

OK I accept, these will be the factors I will aim for.

Failure will be shear.

The strength of each floor support will be at least 3 times the weight of 1 floor. (safety factor of 3+)

The mass initiating the collapse will be less than 15% mass of the total floors combined.

Failure will progress all the way to the bottom.

No problem.

Is there any parameters you or Anok would like to add or change before I build it.

reply to post by waypastvne


Sounds like it will be a very interesting experiment regardless of what results are achieved.

The mass initiating the collapse will be less than 15% mass of the total floors combined.

Will this be a replica of the lower floors (to allow for any crush-up effects) or just a solid mass?

Hi

I re-joined ats today because I thought Simple Math would show no extra energy was needed. I feel that several people showed this adequatily.

Then I saw this went on for 22 pages, and included most of the standard internet miscommunications.

BUT I'll still bravily make my post.

Simply Math say there was lots of energy in the collapse regardless of how you express it: pounds/foot, joules, or watts. There was lots of energy to turn Concrete into dust and damage the surrounding buildings.

Is there evidence of conspiracy? Yes, just ask the terrorists.

Dead Steve

Anyone ever make a BBQ and use the tubes that you put the briquettes or charcoal in, and stuff some newspaper in the bottom... then light the newspaper so the charcoal burns?

Well, there you go.

The towers were "hermetically" sealed from the ground up, and any "fresh" air was introduced by the ventilation system either from the ground or from the top.

What does that have to do with anything, you may ask?

The heat from fuel burning causes air to rush up, just like the BBQ lighter mentioned above. It raises the temp of the fires. Even if air can't get to the fires, temps can still raise. Since heat "rises", air will rush in from the bottom, escalating the temps at the top, and eventually, something in the middle will give... particularly any metal that may be heated by the fires.

Anyhow....

Nevermind.

Originally posted by DeadSteve1234

Simply Math say there was lots of energy in the collapse regardless of how you express it: pounds/foot, joules, or watts. There was lots of energy to turn Concrete into dust and damage the surrounding buildings.

That is true, but unless you also calculate the force/energy of the bottom section that will be pushing up against the falling mass, equally, you have only done half the calculation.

Equal opposite reaction laws always applies, always.

reply to post by waypastvne

OK I accept, these will be the factors I will aim for.

Failure will be shear.

The strength of each floor support will be at least 3 times the weight of 1 floor. (safety factor of 3+)

The mass initiating the collapse will be less than 15% mass of the total floors combined.

Failure will progress all the way to the bottom.

No problem.

Is there any parameters you or Anok would like to add or change before I build it.

Yes, you must be able to demonstrate will never be arrested, it must be a "perpetual machine" in that if you added more layers it would continue.

It must also be not be a domino or avalanche model which is initially quasi-stable. It must be able to resist the actual load at rest in the direction it is exerted during the collapse, even though that may be traveling at a speed in the actual experiment.

But it must progress at similar accelerations to a domino or avalanche progression, it can't be a progression with obvious steps or changes in direction.

I also can't be a simple single point failure collapse of an unbraced structure such as a Kapla tower collapse where the base is simply removed, since that technically is what the truthers are claiming happened:







That should cover it.

(basically NO CHEATING, the system should behave in the physical manner you describe WTC 1&2 behaving)

reply to post by abecedarian

The towers were "hermetically" sealed from the ground up, and any "fresh" air was introduced by the ventilation system either from the ground or from the top.

No they were not, most of the exterior surface area was covered in things known in the trade as "windows", sorry to use jargon here but you can research the technical meaning of the term on the internet.

What WAS hermetically sealed was the elevator shafts, none of which ran the entire height of the building.

Oh, and then there is the little complication brought about by the fact that the fires were at the TOP if the building not at the bottom and the failure started at the very lowest at the level of the visible fire-line...

I love the "theories" that OS'ers have in their heads. When you actually get them to say out loud what they think happened it just makes the whole thing so much more ludicrous.

Originally posted by abecedarian
Anyone ever make a BBQ and use the tubes that you put the briquettes or charcoal in, and stuff some newspaper in the bottom... then light the newspaper so the charcoal burns?

Well, there you go.

The towers were "hermetically" sealed from the ground up, and any "fresh" air was introduced by the ventilation system either from the ground or from the top.

What does that have to do with anything, you may ask?

The heat from fuel burning causes air to rush up, just like the BBQ lighter mentioned above. It raises the temp of the fires. Even if air can't get to the fires, temps can still raise. Since heat "rises", air will rush in from the bottom, escalating the temps at the top, and eventually, something in the middle will give... particularly any metal that may be heated by the fires.

Anyhow....

Nevermind.

One problem though. I have never experienced that coal has produced temperatures that would melt or weaken a steal BBQ because there was to much ventilation.

Burning fuel can only produce a specific max temperature within idle isolated conditions (a furnace). Even then it will not melt steal. Because heat expands, and as it expands temperature are reduced.

WTC was never a isolated furnace that could produce the heat needed to melt steal structures.

reply to post by spy66

Burning fuel can only produce a specific max temperature within idle isolated conditions (a furnace).

*ideal*

But yeah, a normal furnace will not melt steel, you need a blast furnace. This is way Europe didn't have cast iron till the middle ages (the Chinese had it long before). Smelting does not involve melting.

These threads are getting worse lets ask the gas man what happened

For a start WHY is the dust cloud by truthers always stated as pulvarised concrete dust,
what about the sheetrock, what about the sprayed on fire protection, what about paint dust
and of course normal dust that would have built up over the years in various areas of the
buildings conveniently missed it seems.

The other thing is the perpetual comparison of this event with simple 2 mass physics
collisions you did at school WHY?

This is a structure if one part fails it can cause other parts to fail this was a TOTALLY
CHAOTIC SYSTEM you cant MODEL IT !!!

Once those planes went through the walls NO ONE can tell what happened, assumptions and
guesses have to be made we will NEVER know what damage was done to what by what be
it debris or fuel explosion or the resulting fire!

The other annoying thing is the various guesses at the mass of these buildings with lots of quotes at 500,000 tons each, I think this fig has been arrived at by a genuine error because of the often quoted amount of concrete used for the project. Lets look at a column detail at base level.



As you can see from the drawing the columns sit on concrete pads not a lot of concrete
as you can see. The concrete used for sub structure work seems to being used as
concrete in the buildings which it is not!

Info on WTC towers details given on floor numbers construction etc

911research.wtc7.net...

911research.wtc7.net...


The floor slabs have about 700 tons of concrete each apart from the service floors.

So 92x700= 64,400 tons even if the service floors added 27,000 tons between them
(using 1500 tons per service floor) thats only 91,400 tons

Also on page linked to for the above drawing it gives you the following figs

Areas and volume (per tower)
gross area: 418,000 m2
area on plan: 4,032 m2
effective floor area: 319,000 m2
volume: 1,754,000 m3

Quantities of steel (structural steelwork in one tower) total: 78,000 tonnes
per square meter gross area: 166.6 kg
per cubic meter: 44.5 kg
per square meter effective floor area: 244.5 kg

Now I have seen a quoted fig of 96,000 tons for steel in a tower.

So if we took that 96,000 + 91,400= 187,400 tons of steel and concrete.

The other problem with tonnage is USA uses the short ton 2000 lbs UK uses 2240 lbs

We also keep getting tied up re the FLOORS each floorslab could REPEAT
ONLY SUPPORT ITS OWN WEIGHT X A SAFTEY FACTOR.

Each floorslab was held up in postion between the core and outer walls
by small bits of angle iron with 2 X 5/8" bolts through them. The floor could only
be as strong as those connections its that simple.
(Before you ask psikey count the trusses and multiply by 2)

When any mass falls on a floorslab the connections of that slab AND THAT SLAB ONLY have to support the increased loading, the floorslab below CANT HELP! each slab is suspended between
core and wall steel NO DIRECT SUPPORT is given to that slab from any of the mass of the building below TO SUPPORT THE INCREASED LOAD THAT is the real problem with this design during collapse!
The slab connections had to try and resist the extra force.

When the upper mass fell it would reach 18 mph in the approx 1 floor drop
for the mass.

This does NOT result in a small increase in load but a huge one! well above the safety factor.

The impulse load generated depends on what distance the slab below it fails,
the smaller the distance the greater the impact force.
ie If the bolts shear or the angles or if the trusses bend before failure this has a direct effect on the impact load.

YOU DONT KNOW THAT WE DONT KNOW THAT SO GUESS WHAT IT CANT BE RULED OUT THAT THIS WAS GREAT ENOUGH TO CAUSE COLLAPSE!

Once the structure starts to fail, WALLS fail we cant see what happens due to the dust
many floors could have fell internally we dont know you dont know.The walls lose
stability once the floors go it's a problem with the design in this situation.

Every picture during construction shows the walls only a FEW feet above the
steel decking EVERY PICTURE!


Taken from second ext link above the following

Note that the buildings are stiffened by the composite steel-concrete floors. The floors are an integral part of the structural system. Without the composite floor slabs, the buildings would soon collapse.

Taken from a truther site!!!!

Looking forward to your replies.

Originally posted by wmd_2008

For a start WHY is the dust cloud by truthers always stated as pulvarised concrete dust,
what about the sheetrock, what about the sprayed on fire protection, what about paint dust
and of course normal dust that would have built up over the years in various areas of the
buildings conveniently missed it seems.

There were not 110 floors stacked up in the footprints of the towers, so they had to have gone somewhere else. Logic dictates they were ejected during the collapse, and the dust we see is concrete along with larger chunks.

The floors were ejected during the collapse whether they were the dust or not actually, unless you can show us the floors still stacked up in the footprints. Where else would they go anyway when the collided and smashed?
If they didn't smash up then once again, why are they not stacked up in the footprints then? You can't have it both ways.

Even FEMA documented this, as you well know as their debris distribution map has been posted many times.

Originally posted by ANOK
There were not 110 floors stacked up in the footprints of the towers, so they had to have gone somewhere else. Logic dictates they were ejected during the collapse, and the dust we see is concrete along with larger chunks.

You mean that conspiracy fantasies dictate they ejected. Logic dictated that the floors fell down, mostly inside the perimeter, and broke into thousands of pieces during both the collapse and the massive impact with the ground.

The floors were ejected during the collapse whether they were the dust or not actually, unless you can show us the floors still stacked up in the footprints. Where else would they go anyway when the collided and smashed?
If they didn't smash up then once again, why are they not stacked up in the footprints then? You can't have it both ways.

Even FEMA documented this, as you well know as their debris distribution map has been posted many times.

edit on 9/20/2011 by ANOK because: typo

Perfect example of a truther fallacy; either the floors are completely intact and inside the footprint, or they are broken into pieces and outside the footprint. Its a false dichotomy. What about the option that they are broken into pieces and inside the footprint?

reply to post by Bob Sholtz


So you choose to ignore my explanation and accuse me of being part of the big cover up? Is that it? Or what do you mean by being aware of who I am?

I dont see how these floors play such a big role. They were a weak link.
Besides, the core and the walls would still be in tacked if the floors broke of its connection points and collapsed in its own foot print. Thus leaving the main structure "core + walls" that is built to support the whole top section very much in tacked.

The top section fell down on the bottom section. That is how the collapse started. The collapse started when the vertical support structure at the impact point no longer could hold the top section in place. That would be the core + walls.

The top section didn't start to collapse because the floors collapsed. When the top section hit the bottom section, the vertical support structure and the floors collapsed at the same time.
There is no way the floors in the bottom section of the structure could have accelerate a head of this collapse to make the vertical support structure (core + walls) collapse equal as fast. Not if you time it.

If the floors and the vertical support structure collapse at the same time; We have a big issue with some physical laws, already mentioned in this topic by some. Because if the floors and the support structure collapse at the same time that means the structure is still in tacked.

Sorry for editing. My english is not my main language

reply to post by spy66


Actually, once the vertical supports are not directly contacting each-other, as is the case in the collapse, there is much less resistance. The collapse did not initiate with the floor below completely intact, and even if it did, the acceleration of the mass would have overcome the horizontal supports and caused shearing, the debris then twisting and bending the vertical supports down with them.

But that's how I see it, and it is an unpopular view here.