I would like to know, why should anybody believe official story of collapses of the 3 WTC buildings on 9-11.
Many qualified scientist don't believe it.
Which qualified scientists don't believe the "official story"? From whence have they received their credentials? In what venues have they stated that they disbelieve?
The reason that people should believe the "official story" is because it is rigorous. It fits all of the known facts of what occurred on 11 September 2001, with a minimum of speculation, and the reports produced that explain the chain of events both up to and after the impact of the airplanes into the towers have been reviewed by at least hundreds -- and more likely thousands -- of individuals with areas of expertise directly relevant to the reports.
And yet, no professional organization of mechanical engineers has come out and said, "We have problems with the NIST report". No papers are being published in peer-reviewed leading trade journals (note: JONES does not count as a peer-reviewed leading trade journal) that call into question the fundamental assumptions of the NIST report, or (as far as I know) the NIST report's conclusions.
When the balance of evidence -- not quotes, not YouTube videos, but hard, substantive evidence -- is weighed, it falls with a resounding "THUD" on the side of the "official story".
If you have hard, substantive evidence that the "official story" is factually incorrect, please present it.