[LINK] sep11info site has better photos than mass media
Thu, 13 Sep 2001 00:06:40 +1000 (EST)
> The initial TV video of the second plane crash did not show the impact -
> I thought the plane had glanced the building and disintegrated. A
> later video showed it flying straight into the guts of the building and
> disappearing *into* it, with the building exploding on three sides. I
> have no idea how a building could remain standing after this. It is no
> surprise to me that once one floor anywhere collapses the whole
> structure will collapse in a chain reaction. I don't understand how an
> architect could be so sure this would not happen. Nor do I understand
> how the building could not immediately collapse or topple when a 767 or
> whatever crashes straight into it.
It seemed that the building did survive the impact and explosion,
otherwise it would immediately tilted and collapsed, rather than after
withstanding one hour of high temperature aviation gas induced fire which
must have weaken or melted the floor supporting structures and the
momentum of the falling floors caused it to fail like pancakes. If the
core central column failed, the tower would have failed like tilted fallen
tree. It appeared that the automatic fire control system could have been
knocked out by the impact or explosion. A vantage point for controlling
the fire was also lost when both towers were on fire.
Long duration high temperature fire can melt steel and powderise concrete
and there is nothing that can withstand it. This is anologous to the
different quality bank safes, the difference is how long can the
safe withstand the oxy-acetylene torch before help arrive.
By coincidence the designer of the WTC was ask about the possibility,
also by coincidence the name of the other designer:
Les Robertson, the Trade Center?s structural engineer, spoke last week
at a conference on tall buildings in Frankfurt, Germany. He was asked
during a question-and-answer session what he had done to protect the twin
towers from terrorist attacks, according to Joseph Burns, a principal
at the Chicago firm of Thornton-Thomasetti Engineers.
Burns, who was present, said that Robertson said of the center, ?I
designed it for a 707 to smash into it.?
Burns, whose firm did the structural engineering for the Petronas Twin
Towers in Malaysia -- the world?s tallest buildings -- said Robertson did
not elaborate on the remark. Robertson could not be reached early today.