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Originally posted by psikeyhackr
The core could have stood by itself without the perimeter and the floors outside the cores.
psik
Originally posted by liejunkie01
This is where you are going wrong,,,,or somewhere in there.
15 floors are not destroying 90....
Originally posted by DrEugeneFixer
What you're missing is the propensity of tall slender structures to buckle, especially if not braced from the sides. This was provided to the core by the perimeter columns, through the composite action truss/slab structure. Without the perimeter columns/spandrels and slab/truss assemblies, the core is significantly more prone to buckling. Are you familiar with Euler's column buckling equation?
...we should be concerned that any lateral distortion of the core, such as might be expected during the collapse, will increase its propensity to buckle dramatically.
In practice, buckling is characterized by a sudden failure of a structural member subjected to high compressive stress, where the actual compressive stress at the point of failure is less than the ultimate compressive stresses that the material is capable of withstanding
Originally posted by wmd_2008
In practice, buckling is characterized by a sudden failure of a structural member subjected to high compressive stress, where the actual compressive stress at the point of failure is less than the ultimate compressive stresses that the material is capable of withstanding
Do you have any idea what the above means
In science, buckling is a mathematical instability, leading to a failure mode.
Further load will cause significant and somewhat unpredictable deformations, possibly leading to complete loss of load-carrying capacity. The member is said to have buckled, to have deformed.
It is not my fault that you can't figure out how obviously IMPOSSIBLE it is for a skyscraper to do that.
Find a picture of the CN Tower in Toronto. The strength of a skyscraper must be similar to that.
But the WTC had to withstand a greater force of the wind because the WTC did not get narrower toward the top like the CN Tower.
The problem is the level of STUPIDITY of the people who think the buildings could collapse.
TEN YEARS and no engineering school talks about building a physical model that can completely collapse.
They don't even discuss accurate data for distributions of steel and concrete.
Thinking the top of the north tower could destroy everything below in nothing but a gravitational collapse is simply pure unadulterated STOOPID!
Originally posted by ANOK
The truss slab structure did not brace the core.
Originally posted by ANOK
The core was a structure within itself, it didn't need the floors to hold it up.
Originally posted by ANOK
The core columns were not slender, they were massive box columns that started at 52"x22"
Originally posted by ANOK
47 of them all cross braced together.
If you think there were zero lateral forces involved in the collapse process, please explain how the massive perimeter columns fell outward quite a distance from the footprint. QED.
Originally posted by ANOK
What lateral distortion? You mean from the planes impact? If the collapse was gravity driven how would there be 'lateral distortion' in the collapse? You know lateral means 'from the side' right?
Originally posted by ANOK
The core did not just buckle, it completely failed and ended up in short sections spread in a 360d arc.
Originally posted by DrEugeneFixer
reply to post by psikeyhackr
The obvious rejoinder is that the CN tower, and all towers taken as a whole, are designed to resist buckling either by incorporating moment resisting connections, or diagonal bracing, which assist each column to transfer forces to its neighbors. This is true of the towers as designed (via the exterior 'chex' assemblies), but not of the core considered alone. It was not designed to resist significant lateral loads on its own, period. once it is deformed even slightly from the perpendicular (ie slight bending), buckling failure will ensue, and thus the structure will fail.
This is not just a theoretical statement. Look at the videos of the 'spire' which momentarily stood following the collapse of the towers. It immediatly goes sideways, as we should expect in a buckling failure, and without any explosions in evidence.
Originally posted by DrEugeneFixer
reply to post by psikeyhackr
Tower appears to be a continuous concrete pillar essentially obviating the need for moment resisting connections, since there are no connections, and the structure itself is designed to resist moment in the way that its concrete 'vanes' are oriented towards the center of mass.
Anyway none of this applies to WTC towers.
Your reasoning ignores the resistance that would be offered by those 90 floors, actually 95 floors.
You have to realise ALL the floors would be effected by the mass of the falling floors, including the falling floors themselves, they are not immune to the forces of the impacts which are equal and opposite in direction.
The first floor of the falling block would be effected by the impact, as much as the first floor of the lower 95 floors.
There is no reason the first impacted floor would fail but not the first impacting floor, which has all the force of the falling floors affecting it as well as the impacted floor.
Just look at this gif again, you can see the first floors of the falling block are failing BEFORE the impacted floors fail.
The tilt of WTC2 also proves you wrong, as the top did not fall directly on the floors bellow it.
The top did not cause the bottom to collapse, period.
Originally posted by ANOK
The top did not cause the bottom to collapse, period.
edit on 12/19/2011 by ANOK because: typo
Originally posted by liejunkie01
reply to post by ANOK
I would also like to add that I have been doing a little research on the viscoelastic dampers that was connected to the truss. The research was conducted after repeadedly sifting through all of the wonderful sites on this subject.
I know I put alot of emphasis on the bolts..........but I also believe that the dampers could have been the weak link. Either way, dampers have a set load limit.......I am currently trying to find it.........but good luck to me....
The connections as a whole(bolts included) were the weak link.
bolts break, dampers break
Sorry for the tone of the last post
The damper and other floor attachment brackets were also a point of failure leading to the towers' collapse. When the intense fire heated the 60 foot-long floor trusses, they eventually distorted and pulled free of their attachments to the exterior columns.