I wanted to take the time to reply to this properly, hence the delay. I think you're a good engineer, Chalo, but I think this is a blindspot for you. We all have them as we're fundamentally irrational beings and use conscious effort to try and over-ride the natural urges to see faces in the clouds, creatures in the shadows and ghosts in the night.
Chalo said:
Punx0r, none of us can tell you what actually happened, because we don't know. Whoever does know isn't saying. And the publicly visible attempts at fact finding sure looked a lot more like they were centered on destroying evidence rather than uncovering it.
I'll agree with you that all information about the attack isn't publically-known and probably won't be for at least 50 years (if ever). That's on balance of probability.
However what might look like destroying evidence to a cynical mind isn't necessarily so. The WTC site was initially and primarily an emergence rescue, then an evacuation, then a search and recovery, then a clean-up. It was also technically a crime site, but there wasn't exactly much police-work to do, since the cause of the disaster was clearly obvious. The forensic analysis of the structural failure was understandably an after-thought.
Chalo said:
But what I do know as a materials guy and structural designer is that failures that never happen anywhere in the world, ever, don't happen three times in the same place on the same morning, in different structures and from different causes.
We've touched on this before. WTC 1 & 2 are a repetition of a single set of circumstances. The construction of WTC 7 was different, so yes, separate case. However, the main drivers were fire (primary cause) and mechanical impact damage (secondary cause). From my limited understanding structural failure is to expected to result from fire in a steel structure.
For your argument to be valid you need to find multiple examples of buildings of similar construction that survived widespread, uncontrolled and sustained fire without collapse. WTC 7's with its tube-in-tube design might be best to focus on because it wasn't hit by an airliner, which probably complicates finding comparable examples.
FWIW, the Truthers seem to equate any high-rise building fire as an equivalent example, but from what I've read, the ones (or parts of) that survived were not comparable (such as concrete reinforced, partially controlled fire, or exterior cladding fire) and the ones (or parts of) that did suffer collapse were comparable.
I'm sure it's possible (and there may well be examples out there) of steel-framed building that are inherently fire-proof due to conservative design (lot of internal pillars). However it seems that the typical response of an economical steel structure to raging fire is structural failure.
Chalo said:
the official findings surrounding the building demolitions (let's call them what they are) only make sense in a world where tall steel buildings sometimes collapse straight down from fire. We don't live in such a world.
Leaving aside fire-induced collapse, it should be obvious a mostly-hollow, non-rigid structure will behave that way. Aside from a little wind the only external force is gravity acting downwards.
Chalo said:
There is an explanation for the events of 9/11/2001, but the official explanation isn't it. And while I can't conclusively identify a specific cause for the structural failures in question, I can point out that the instantaneous appearance of the USA PATRIOT Act and the Department of Homeland Security makes a strong circumstantial case as to who was responsible and why they did it.
I think you're confusing correlation and causation here. There was almost certainly (balance of probability again) some political exploitation of the attack. Politicians are always looking to promote their interests and government agencies and departments looking to increase their responsibilities and power.
All sorts of legislation and plans sits waiting for future scenarios (Ref: Cold War events planning). Following the recent attacks in Paris they quickly declared a state of emergency, with extra-ordinary police and military powers as an arguably necessary response to an on-going immediate public danger. Spin in slightly and the attack was staged in order to implement pre-prepared plans to implement military rule/police state.
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