You know what debate me 9/11 was not an inside job.

Originally posted by Seymour Butz
Also, there's something I remember about the KE and how the energy is squared.. or something similar. Wouldn't that mean that a LARGE amount of KE could be absorbed, and still not be discernable in a youtube?

Kinetic energy from gravity can only be obtained from the potential energy stored in the building (MGH). When potential energy is converted 100% to Kinetic energy, there is free-fall acceleration.

Kinetic energy is 1/2mv^2

Maybe that is where you are getting the idea that there is a square there?

The energy is not squared as KE means kinetic energy.

So, I'm not really sure your point here.

If indeed the kinetic energy was squared, that energy DID NOT come from gravity but another outside source.

reply to post by Griff


A good example of potential energy being converted into kinetic energy is a roller-coaster. But even a roller-coaster that is designed for such a conversion hits resistance. It hits friction from the track, friction of the wheels themselves, air resistance, and converts some of the potential energy into thermal energy.

Can we now say that a 100% conversion of potential energy into kinetic energy of a building collapsing into itself (not falling onto itself) is extremely fishy? IMO, yes it is.

Originally posted by Seymour Butz
In the other thread about the plane going through the ext columns, you mention welds being the weak point and breaking, etc.

Yes, the plane's force would be in shear (perpendicular to the columns). Welds are weaker in shear than they are in compression. And weaker than the tensile strength of steel.

Why do you believe that the columns must buckle, in order for it to fail?

When have I said that they "must buckle"? I'm sure you'll find that I rarely state such unequivocal, absolute statements. If you ask your brother, he will tell you that we are trained not to do so. It causes liability issues.

For example: I can not state that I "inspected" a building. Because that word encompasses much more than observation of the building's exterior. I can state that I observed the building's facade or noted issues with the building, etc., etc.

Hopefully, now you will notice this and stop placing such extreme words in my mouth.

Originally posted by Griff

1-Kinetic energy from gravity can only be obtained from the potential energy stored in the building (MGH). When potential energy is converted 100% to Kinetic energy, there is free-fall acceleration.

2-Kinetic energy is 1/2mv^2

So, I'm not really sure your point here.

1- we agree

2- oops, I had it backwards. What I was trying to say is that useing that equation, if 10% of the kinetic energy was absorbed by the structure's destroying itself, then velocity would slow by the square root of 10, right? Or 3.3%

Originally posted by Griff

1-Yes, the plane's force would be in shear (perpendicular to the columns). Welds are weaker in shear than they are in compression. And weaker than the tensile strength of steel.

2-When have I said that they "must buckle"?

1- Ahh, ok then. But since many/most of the core columns in the towers broke at the welds, wouldn't 7 also show the same characteristics?

2- you didn't. You said that buckling columns would absorb KE, and I'm asking if this is the only possible failure mode. Nothing else. Cuz I believe that breaking welds/bolts would absorb LESS KE when they break, right?

Which of course leads to the obvious question of just how much KE could be expected to be absorbed.

And on and on...

Originally posted by Seymour Butz
2- oops, I had it backwards. What I was trying to say is that useing that equation, if 10% of the kinetic energy was absorbed by the structure's destroying itself, then velocity would slow by the square root of 10, right? Or 3.3%

The point is that with free-fall acceleration, there can not be any energy absorbed by the structure destroying itself. Or there would not be free-fall acceleration to begin with.

Originally posted by Griff

Originally posted by Seymour Butz
2- oops, I had it backwards. What I was trying to say is that useing that equation, if 10% of the kinetic energy was absorbed by the structure's destroying itself, then velocity would slow by the square root of 10, right? Or 3.3%

The point is that with free-fall acceleration, there can not be any energy absorbed by the structure destroying itself. Or there would not be free-fall acceleration to begin with.

Yes, I already agreed to that.

So am I correct?

Originally posted by Seymour Butz
So am I correct?

I'm getting about 3.7% difference using a slightly different method than you, so yes I'd say you're correct in this.

But, remember this:

I calculated that with 10% absorption of the energy, the velocity would be 26 m/s instead of 27. In the 2.25 seconds that free-fall acceleration was observed, there would be a difference of 2.25 meters. That is 7.4 feet and 60% of a regular building story. Which I believe would still be discernible, even in a youtube video. So, therefore the energy sink had to be less than 10% IMO.

[edit on 1/24/2009 by Griff]

For the volumes of analysis of the WTC collapses, it's notable what's missing: a fundamental flaw in the design.

My favorite for this is the Sampoong Department Store collapse in 1995. Unlike the Sampoong collapse, no structural faults could be discovered in the WTC design or maintenance.

The Sampoong Department Store collapse took 20 seconds to collapse 5 floors.

It created this.

Further investigation revealed that the building was built using a technique called "flat slab construction," which consists of strengthening concrete columns supporting the building with steel bars, and floor slabs with more steel. However, blueprints of the building showed that the concrete columns were only 60cm in diameter, below the required 80cm. Worse still, the number of bars reinforcing the concrete was 8, half of the required 16, giving the building only half the strength needed. Steel slabs that strengthen the floor were also unsatisfactory: They were 10cm from the top of the floor when they should have been 5cm, decreasing the structure's strength by about another 20%.

...

The final change that brought the building down was, ironically, installation of a safety feature. Fire shields were installed around all escalators to prevent the spreading of fire from floor to floor, but to install them, the builders cut into the support columns, reducing their size even further. The columns were no longer able to properly hold up the concrete slab, and would eventually punch shear through the ceiling, whereby the column would punch a hole through the ceiling, instead of supporting it.

www.nationmaster.com...

20 seconds for 5 flat-slab concrete floors that collapsed due to faulty construction, weakened steel support beams, and a final stress event (the sliding of a 4 ton air conditioner across the roof).

Would the assumption of the weakening of steel beams due to the heat of the fire be analogous to the situation at the Sampoong Store?

If I were truly invested in coming up with some "eureka!" material, one might compare the KE evident in the Sampoong Dept Store collapse with the estimates being made in this thread.

Something tells me that 10% sink might be a bit too low... without a huge flaw in the construction and/or tampering with the support columns.

Could it be so simple that the WTC towers were flawed? If they were, no insurance money would ever have been paid as a result of the collapse... 3.5 billion reasons for a cover-up right there.

If they weren't flawed, does that not then mean that tampering was involved?

My argument assumes all things being equal, which I'll absolutely leave open for debate. Sampoong's columns were steel-reinforced concrete and not pure steel, but would not the appropriate calculations still apply? Would not the resistance provided by the columns in the WTC be higher?

[edit on 25-1-2009 by cogburn]

Originally posted by cogburn
My argument assumes all things being equal, which I'll absolutely leave open for debate. Sampoong's columns were steel-reinforced concrete and not pure steel, but would not the appropriate calculations still apply? Would not the resistance provided by the columns in the WTC be higher?

I think you've made a fair assessment.

Let's rehash.

A shoddily built building took 20 seconds for 5 stories to collapse.

Supposedly one of the heftiest buildings built (WTC 7...remember that it was a bunker) took 6 seconds to collapse 47 stories.

With all things being equal, Occam would say that the 47 story building had help to collapse.

Originally posted by Griff

I'm getting about 3.7% difference using a slightly different method than you, so yes I'd say you're correct in this.

But, remember this:

I calculated that with 10% absorption of the energy, the velocity would be 26 m/s instead of 27. In the 2.25 seconds that free-fall acceleration was observed, there would be a difference of 2.25 meters. That is 7.4 feet and 60% of a regular building story. Which I believe would still be discernible, even in a youtube video. So, therefore the energy sink had to be less than 10% IMO.

As it turns out, beginning time has a large effect on acceleration.

Dr Greening, while I wouldn't rely on him solely for structural stuff, is certainly as qualified as Chandler to do this. He gets a value of 9.2m/s^2 +/- .6m/s^2 just by shifting the time plot by .1 second.

the911forum.freeforums.org...

The original plot fits to:

Drop = -0.077t^3 + 4.8433t^2 -0.2123 t + 0.0669

And the plot shifted by 0.1 seconds gives:

Drop = -0.0176t^3 + 4.4721t^2 - 0.5854t + 0.0034

Hence for the acceleration, by double differentiation, we have:

Original plot:

Accel = 9.6866 - 0.462t

Plot shifted by 0.1 seconds:

Accel = 8.9442 - 0.1056t

Thus we see a marked change in the calculated acceleration for just a 0.1 second shift. This is why I have argued that the measured acceleration is about 9.2 +/- 0.6 m/s^2.




Would less than 10% be probable, if welds/bolts need to be broken, rather than column buckling?

I think I read a post from you that stated that the connections were typically the weak point, or something similar.

Originally posted by Seymour Butz
Would less than 10% be probable, if welds/bolts need to be broken, rather than column buckling?

I think I read a post from you that stated that the connections were typically the weak point, or something similar.

It all depends on their design etc. I haven't studied WTC 7's connections in enough detail to answer your questions.

Originally posted by Griff

It all depends on their design etc. I haven't studied WTC 7's connections in enough detail to answer your questions.

fair enuf.

i would expect bazant to do it some day.

then we'll see if the expected results could indeed be seen in a video.

thx 4 the 411

this right here is a good read on it being a planed job

it even describes back in 2001 what is happening today with the economy

good read


www.scribd.com...

[edit on 29-1-2009 by lycopersicum]

911 total inside job. look at this video. the masses agree.

/watch?v=nlPweD6R3Cc

watch that!!!!!!!!1