You have not explained why the top of WTC 2 went west. And of course
this image proves the concrete core, ONE MORE TIME.
Ok, I'm really having a hard time understanding what your image is supposedly proving. I see a whole bunch of debris and large chunks of the exterior wall of the WTC falling down. I don't see how this proves a concrete core. Images that would prove a concrete core include:
Unobstructed views of the entirety of the WTC during its construction
Noterized blue-prints calling for a concrete core
Published specifications naming one specifically
This is a
concrete shear wall holding up the stpire which is formed by an interior box column. NOTICE:
No core columns in the core area to the left.
Then, the legendary
WTC 2 concrete core.
And what about the 17 foot thick concrete
core wall at its base AGAIN, no steel core columns where they should be, like protruding from the stairwell, right of the stairwell, in the fore ground.
It's time to nip this claim. Do you believe that there was no steel holding up the WTC towers? If that's true, let's redesign the building without a steel frame:
At 210ft per side and a live load of (250lb/ft^2 *1.6 + 100lb/ft * 1.2) (ASCE 6) I get a load of 70E3 kips per floor. Now, the WTC towers were a cantilevered structure, meaning that the majority of the load was transferred from the outer edges to the center of the structure via a series of moment connections at each floor. For a beam spacing of 10 feet on center, I get a distributed loading of 16kips per linear foot. That means a moment connection of wL^2/2 or (16kips*210^2)/2 or 352,800ft-kips. The thickness required for a cantilevered beam whose moment connection is 352,800ft-kips with an area of steel equal to the maximum 1.81% is 4653 feet. Oops, seems a little odd, eh?
Ok, so clearly there was some steel in the flooring system. A steel box frame eliminates one of the big problems with using reinforced concrete which is that you can't just put as much steel as you want in there in order to meet the design codes.
Alright, let's look at the shear wall. Buildings with load bearing exterior walls, including mid-range high-rises require vertical shear reinforcement as a protection primarily against wind. The NIST report lists a load sharing system between both internal and external support columns. It is interesting to note that the external columns, in the case of the WTC, acted in both a shear and gravity load bearing capacity.
Now to a little bit of structural mechanics. The capacity of a shear wall is governed by the addition of the shear capacity of the steel and the concrete. The concrete shear capacity is governed by the length of the wall and it's (assumed) horizontal width. See ACI Section 11.10.3 for the set of governing equations.
If the shear capacity of the structure in the WTC towers were governed exclusively by a shear wall at the center of the complex (assuming no steel in the outer structure), let's take a look at your 17 foot value for the base of the structure. Using my equations, I find the shear capacity of a 17 foot thick shear wall to be 65,000 kips or the equivalent wind loading from a storm producing 230 psf of pressure on one face of the WTC. Using Bernouli's equation for static pressure load, I get a wind velocity of 304 miles per hour. Those calculations are, of course, neglecting the 3 inch thick steel you've also claimed to see. If I add your steel to the concrete core, I get 1311 mile per hour winds. Seems a bit, well, overdone, don't you think?
Here's the kicker, shear walls don't change their width as the building progresses higher, they only change the spacing of the steel, so if you're seeing 17 feet at the base, you've also got that to the highest part of the building.
For the sake of argument, let's take the 17 foot thick core wall and calculate the load capacity and see if it's actually thick enough to hold the building up. The wall is basically doing the work of a column by supporting vertical loads, so let's split the wall up into columns. At 17 ft thick and let's say 102 ft/side of the core, that gives us a nice round 6 columns. We'll asssume they're square, even though that makes the geometry impossible. A 17ft thick column with a series of 100 3 inch bars has an area of steel of 300 square inches and a gross area of 41,616 square inches meaning that the maxiumum design load according to ACI Equation 10-2 is 7.3 billion pounds per column times the 6 columns is 43 billion pounds. Using my earlier calculation of 70,000,000 pounds per floor * 110 floors, I get 7.7 billion pounds or a factor of safety of 5.58. It's way too much, not to mention space consuming.
Let's review, the shear wall you've got is way too thick and you've got 5 times more concrete than you need to hold the structure up. Let's also not forget that reinforcing bar sizes only go up to 18, or a diameter of about 2.2 inches. Anything else would be too large for the iron workers to safely lift and weld into place.
If you've got more concrete than you need, why put any steel in in the first place?
Here's the point, since I'm pretty sure you're not going to read most of that: If the concrete existed, why would the designers have added steel to the structure? You've got 2.254 million cubic feet of concrete that no one has ever claimed existed including the structural engineers and general contractors. That concrete takes up all of the space for the steel and would have required a vastly different workforce. Concrete workers instead of steel workers, ready-mix trucks instead of steel loaders. The bill of materials would have included the concrete, along with the reinforcing steel, formwork and truck work. Why, then, do you insist on providing blurry photographic evidence? If a massive cover-up existed on the part of the contractors more than 30 years ago, why didn't anyone notice?
If no one is going to take the socks, I'm going to take them for a while until I get a response to this post.
in the thread. His question was about the order the towers fell.
