You are incorrect. the WTC collapses had to be controlled demolitions for the three core reasons- 1) molten metal witnesses and video evidence 2) free fall collapse acceleration (NOT pancaking) 3) vertical collapse of WTC7, overwhelmingly damaged on the south side, and hardly damaged on the north side at all.

Moving the goal post. I responding to you (or perhaps the other poster in this thread) who said that progressive collapse of a steal structure was never documented prior to 9/11. I showed that as false, and how you responded was irrelevant to the categorical fact that they have occurred in the past.

I'll address your claims too. 1) molten metal witnesses and video evidence. Correct. It does seem to be molten metal. It is not indicative of steel, however, and fits the characteristics of melted aluminum "Visual evidence already discussed shows that significant wreckage from the aircraft passed through the building and came to rest in the northeast corner of the tower on the 81st floor, i.e., at the location where the molten material apparently originated. Much of the structure of the Boeing 767 is formed from two aluminum alloys that have been identified as 2024 and 7075 (NISTSTAR 1-3). The melting points for these alloys vary as the material melts. The Aluminum Association handbook (The Aluminum Association 2003) lists the melting point ranges for the alloys as roughly 500C to 638C and 475C to 635C for alloys 2024 and 7075, respectively. These temperatures are well below those characteristic of fully developed fires (ca. 1000C), and any aluminum present is likely to have been at least partially melted by the intense fires that had been in the area for nearly 48 min." (NISTNCSTAR 1-5A Chapter 9 Appendix C

p.p. 375-376 (pdf p.p. 79-89)) Coincidentally, aluminum is an ingredient in thermite.

I highly recommend reading the whole report for yourself in the link below.

2) free fall collapse. Dr. Frank Greening's paper on this is probably the most thorough investigation into this seemingly baseless claim, however it can be refuted categorically with a few basic facts. One: in the videos and photos of the collapse one can see columns and other heavy debris far outpacing the collapse of WTC7. Two: one can also see dust debris falling at approximately the same speed of the building, which proves it was falling well below freefall speed. Three: Dr. Greens paper (which I will link below) give physical models of WTC7's collapse, and the energy transfer which increased its momentum with each "pancake", which is not possible if it was falling at freefall speed, and is conclusive proof of a progressive collapse.

So why does this ludicrous claim keep appearing? Deceptive video editing, and the memetics behind a useful rhetorical factoid. From debunking911 "Deceptive videos stop the timer of the fall at 10:09 when only the perimeter column hits the ground and not the building itself. If you notice, the building just finishes disappearing behind the debris cloud which is still about 40 stories high." Every report in existence refutes freefall including the videos themselves.

3) vertical collapse of WTC7, overwhelmingly damaged on the south side, and hardly damaged on the north side at all. You are beginning to strike me as a person who doesn't read the arguments against his claims. Multiple computer and physics models (as previously mentioned) show conclusively the cause of collapse at WTC7. Nevertheless, I'll reiterate some important facts verbatim from the mouths of 9/11 investigators and experts:

(the following is from the PM article. find the link below)

Videos of the fall of WTC 7 show cracks, or "kinks," in the building's facade just before the two penthouses disappeared into the structure, one after the other. The entire building fell in on itself, with the slumping east side of the structure pulling down the west side in a diagonal collapse.

According to NIST, there was one primary reason for the building's failure: In an unusual design, the columns near the visible kinks were carrying exceptionally large loads, roughly 2000 sq. ft. of floor area for each floor. "What our preliminary analysis has shown is that if you take out just one column on one of the lower floors," Sunder notes, "it could cause a vertical progression of collapse so that the entire section comes down."

There are two other possible contributing factors still under investigation: First, trusses on the fifth and seventh floors were designed to transfer loads from one set of columns to another. With columns on the south face apparently damaged, high stresses would likely have been communicated to columns on the building's other faces, thereby exceeding their load-bearing capacities.

Second, a fifth-floor fire burned for up to 7 hours. "There was no firefighting in WTC 7," Sunder says. Investigators believe the fire was fed by tanks of diesel fuel that many tenants used to run emergency generators. Most tanks throughout the building were fairly small, but a generator on the fifth floor was connected to a large tank in the basement via a pressurized line.

Dr. Greenings paper of the freefall fallacy: http://www.911myths.com/WTCREPORT.pdf

Another interesting page on the freefall fallacy. Includes several noteworthy calculations of freefall speed vs. the actual collapse.

http://www.debunking911.com/freefall.htm

WTC7 Collapse

http://www.popularmechanics.com/ technology/military_law/ 1227842.html?page=5#wtc7