Posted on 09/10/2009 3:46:28 PM PDT by Moseley
You are correct in so many ways, about the load-shifting, how it tries to transfer load-stress horizontally across a floor, so that that load-shifting and continuing vertical support below undamaged areas of the same floor, will keep that floor “upright”, and how the general result of that dynamic will tend to focus the total affect of the load-shift to the core. Yes.
But, it was the combination of the nature of some of the catastrophic damage that took place, and the unique nature of the structure of the Twin Towers that MIGHT, taken together, have both contributed to the initial-collapsing floors and also worked to concentrate the weight of the collapsing load towards the core.
The uniqueness of the Twin Towers was that unlike most (most all, I believe) similar looking high-rise buildings, the vertical support design of the structure WAS different.
With most all other high-rise buildings, the outer-most vertical elements, that are clad with an exterior finishing material (the curtain wall you see when you look at the building) are but one series of many such series of vertical supports, from the outer-most wall to the inner core of the building.
That was not the case with the Twin Towers.
One of the selling features that the planners pitched with the Twin Towers was that the tenants’ space (and laying it out) would NOT be encumbered by dozens of vertical support pillars running through the space between the windows and the building core.
The outer-most wall (the steel girders it was made of) WAS the “other” vertical support besides the inner core. There were not multiple sets of vertical pillars between the outer-most wall and the core.
However, and in fact, due to the “load-shifting” calculations resulting from that design, a contract for specially designed and specially hardened steel girders was given to a Japanese company, just for the Twin Towers, because, until the Twin Towers, girders to those specifications had not ever been made.
The other feature they employed, to strengthen the floors, help carry the load across a larger open (vertical support free) space, and assist in the horizontal load shifting, was that the steel girders of the “floors” were not a simple one-dimensional horizontal placement of girders.
They were constructed as trusses, where a “single span” consists of an “upper” and a “lower” member joined in multiple places from end to end by diagonal uprights between the top and bottom of the truss. Just think of two parallel lines with a sort of continual “z” configuration running between them. That’s a truss. And the trusses are what joined the outer-most walls with the inner core (made the “floors”), with no vertical supports in-between.
I don’t think any engineers have confirmed that the design elements and how the structural elements worked and how they were affected by the particular damage they received was the cause of the very start of the “pancake” affect. But, as far as I know, no architects, since 9/11 have proposed buildings that employ the unique vertical design feature of the Twin Towers, for buildings so large - a single outer-edge vertical support system with no other vertical support until the core.
I have never seen any 9/11 truther explain how explosives could have survived the plane crash, assuming they could hit the exact floor where the explosive were planted. You can’t tell floors from the outside. Especially from a plane traveling 350 mph.
Actually, it was 540 MPH, which makes your point stronger.
Even if the demolition explosives were not destroyed by the impact, they would have been detonated prematurely by the blazing fire which ran from 903 AM to 9:58 AM in one tower and from 8:45 AM to 10:28 AM in the other tower.
And anyelectronic controller devices would have melted in teh fire and would not be operative.
And then again WHERE would the demolition explosives be installed? The WTC architectural design did not include convenient empty spaces for installing bombs. During normal demolition, explosives are strapped on the outside of the support columns, where they are very obvious and visible. But in the 9/11 conspiracy theory alternate universe, the explosives had to be invisible to the 50,000 workers and staff in teh WTC.
So someone would have to open up the walls, install explosives against the support columns, then seal up the walls, mud them over with drywall joint compound, wait for the joint compound to dry, sand the joint compound smooth, paint the walls, and then wait for the paint to dry. But there woudl be no room in the wall for explosives.
Dear ExGeeEye: After reading your very compelling story about the advance prediction from your sister’s friend, the Finnish engineer, that the buildings would fall exactly as they did....
.... I find myself wondering if perhaps we should listen to professional architects and engineers when trying to understand what happened on 9/11?
NAAAH!!!
It is so much more fun to grope in teh dark and imagine all kinds of things without knowing what we are talking about.
Why everyone is so determiend to NOT listen to people who build buildings and design buildings is astonishing.
By the time the combined wreackage hit an undamaged floor it was heavy enough to break an unweakened floor, so the collapse continued down the building (You can see windows blowing out sequentially as it happens.)
Now you have the intact building section above the impact zone sitting on top of a hollow tube. Piston. Crush. The central building core guides it down.
The Tower wasn’t leaning. The very top of the roof was dipping on one side due to warping of steel.
Why would clear facts change the mind of Charlie and friends?
Like little children the left wants to have it both ways...stupid is just not strong enough of a word...
The "apparent explosion(s)" were not explosions at all. They were, very simply, due to the "piston effect": As each upper floor in the growing "stack" of falling floors fell onto the floor below it, the air, smoke flame, dust, and contents of that lower floor were "squeezed out" and displaced laterally in a big "puff".
No explosions. No mystery. Simple high school physics...
The steel did not "melt"
Watch a blacksmith at work, and you will see that steel heated to red heat is so soft that it can be molded like putty by the blacksmith's hammer.
Furthermore, that once-strong steel, when cooled slowly, is so weak it can be bent with your bare hands (that's called "annealing").
Returning the steel to its prior strength and hardness requires re-heating it and "quenching" it by plunging it into water to cool it quickly.
Watch a blacksmith forge a knife. You will never again be amazed that the girders in the WTC -- when exposed to tons of burning jet fuel -- weakened to the point that the buildings collapsed.
Chemical Engineer Rosie O'Donnell has pointed out "fire can't melt steel".
But as you say, melting is not necessary for the girders to lose structual strength.
THE careful text-books measure
(Let all who build beware!)
The load, the shock, the pressure
Material can bear.
....
“Now you have the intact building section above the impact zone sitting on top of a hollow tube. Piston. Crush. The central building core guides it down.”
Its interesting that you used the term “hollow tube”.
A “rigid hollow tube” is a term the designers used to describe their unique design.
http://www.skyscraper.org/TALLEST_TOWERS/t_wtc.htm
Any moron with some ability in Arithmetic and common sense could have predicted the result.
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