that's why friendly companies like Marsh USA and Fuji Bank just happened to be located on those floors.

If you knew how the WTC Towers and WTC 7 were designed, then you would know that these buildings were unlike most other hi-rise buildings.

The Towers were the first skyscrapers to use steel curtain walls, that were load bearing and a steel central core.

The Towers were then split into thirds by the mechanical floors. These floors created the darker bands around the building. They used beams instead of trusses and heavier columns. Because they used beams on the mechanical floors, the curtain wall columns line up evenly, creating seams around the building. On the regular floors the column heights are staggered making a stronger joint.

At the top of the Towers was another unusual feature, the hat trusses. The hat trusses held everything together. Blow up the hat trusses and the building should split like a banana.

Oh and one more important feature, the 81st floor. The floor where Steven Jones has shown that thermite was pouring out of the NE corner of WTC 2. The 81st floor was also a mechanical floor. This is where they installed the dozen, 24 ton elevator hoists. The same floor that Fuji Bank decided to add even more load right before 9/11, when they installed a load of battery backup units.

The result is that in steel grid construction, you have to wire the whole building. This was not necessary in the Twin Towers. If you attacked the core (easy to do via the elevator shafts), the mechanical floors and underneath the hat trusses, you could do a top down demolition and that was probably the only way to bring the buildings down.

Now go back and look at the impact zones, the floors they picked were not by accident.

Then there's WTC 7. WTC 7 was a very odd building. It used the same design as the Towers, with a steel core and a steel curtain wall. However, the main mechanical floors were down on floors 5 - 7. Floors 5 - 7 are also where the cantilevered trusses were located. WTC 7 used cantilevered trusses to hold up friggin 49 floors. They did this in order to build on top of a Con Ed Substation. Whose brilliant idea was that? But this is why WTC 7 was dropped from the bottom. Again, no need to wire the whole building. Blow out the core, the mechanical floors (including Rudy's extra strong OEM Bunker) and the cantilevered trusses and I'm sure gravity will take care of the rest.

WTC 7 had one more big problem, fuel load. There was an enormous amount of fuel stored in numerous places around the building. If anyone wonders why FDNY doesn't want to know what really happened, it's because there is a lot of blame to go around and whoever allowed an office building to be built on top of a major substation and then allowed the build to be loaded up with assorted fuels, should be in jail for a long time, regardless of whether or not they knew about the attack in advance.

a buiding "pancake collapsing"? I think not. I'd say erupting/exploding is more like it.

----------------------------------------------------------------------------------
Consider mass emailing truth messages. More info here: http://www.911blogger.com/node/13321

There are plans for destruction of bridges (as well as certain roads and railways, I'm sure), since doing so slows down an invading army's progress through the country. Rigging buildings does not serve a similar purpose.

OTOH, I am not convinced this is such a far-fetched idea. As you said, it's enough to pre-plant the wiring. After all, the time consuming part is doing all the required math; the rest is mere physical labor. Top-down demolition is possible with wires, I don't see any problem there: the trigger signal may not reach the topmost part, if it's already been destroyed, but it will reach all the segments beneath it.

As for the top-down vs. bottom-up demolition - it's true that the known instances of CD go bottom-up, but note how different a typical building is from WTC. Most buildings have a relatively wide "base" and are relatively low, while WTC 1 and 2 were the opposite: the base was relatively small compared to their height. Would a bottom-up CD be possible at all in that case? Wouldn't the towers keel over and tumble "sideways" if you started by pulling out the lower floors from underneath the top structure?

Truthers have paraded at least one known example of top-down demolition.

I've wondered about the same thing: would it be safe to demolish a very tall and narrow building from bottom up? Top-down would appear safer to me in such cases. In practice, such buildings would probably be demolished the way the Deutsche Bank Building is currently being "demolished".

Sorry, Exploded as well- note the horizontal forces outside the perimeter walls. A bit of both techniques probably helped to bring 1 and 2 down.