The lessons of 9/11
BY RITA SHERROW World Television Editor
Sep 3, 2006
4/21/08 at 11:33 PM
Film describes safety factors learned by towers' failure
Ground Zero is a disturbing
place.
It was much more than
disturbing to Leslie Robertson,
chief engineer of the World
Trade Center, who watched
from his office as the iconic
towers burned and collapsed
on Sept. 11, 2001. More than
2,700 people died.
"I cannot escape the
memory of the people who
died," he says in the new
"Nova" documentary "Building
on Ground Zero" airing
Tuesday on PBS.
Larry Klein, producer of
both the 2002 film "Why the
Towers Fell" and of "Building
on Ground Zero" said making
the new documentary forced
him to revisit what happened
on the day of the terrorist
attacks.
"It was pretty traumatic and
dramatic . . . I didn't want to
look back," said Klein, in a
recent phone interview from
his Boston base.
". . . Frankly, all the effort
that has gone into analyzing
what happened has been, in
part, to set the record straight
about why the towers fell, but
also to see if that event
revealed any major problems
in buildings that need
correcting," Klein said.
"I said, 'If we want to do a
program on how can we build
safer buildings, then I'm happy
to do it.' "
Approximately 30 percent of
the footage in "Building on
Ground Zero" was gleaned
from the first film. Klein said
he made a concerted effort to
leave out horrific footage of
the victims.
"But, some of the survivors
like Brian Clarke appear again
because, to me, it is so
important to have a first-person
perspective of what it was like
to try to get out of that
building," he said.
Klein didn't want people to
forget about those who did
survive.
"They are very positive
people. They talk about the
five-year anniversary and want
their word to get out. They
didn't want to wallow in the
past. They wanted this event
to leave some kind of positive
legacy."
The 2002 film recapped the
findings of a six-month
investigation by the American
Society of Civil Engineers
(ASCE). That report
determined that the floor
trusses gave way after
sprayed-on fireproofing was
damaged, exposing the steel
trusses to 2,000-degree heat.
The truss failure caused the
buildings to "pancake," floor
by floor.
"Every single expert we
talked to basically explained
the collapses in the way that
we explained it in 2002," said
the award-winning producer.
In 2002, Congress gave The
National Institute of Standards
and Technology a directive to
analyze what happened to the
towers. The result of that
study showed there was "no
structural element to blame for
the buildings' collapses."
The steel trusses, which lost
their fire protection when the
jets plowed into the buildings,
did what they were supposed
to do, Klein said.
But those trusses were not
built to withstand the severe
temperatures generated by
jetliner fuel-fed fires.
The trusses bowed from the
heat, eventually breaking the
supporting columns to which
they were attached. That is
what caused the collapse of
the towers, the NIST reported.
"The finger was pointed at
those floor trusses and they
weren't the culprit. In fact,
they were so amazingly robust
that they actually bent the
columns," said Klein.
"So, in a way, this is not
only a vindication for
Robertson (who is leading the
engineering team on the
107-story World Financial
Center under construction in
Shanghai, China) but a real
important point for people who
are building structures in the
wake of 9/11," he said.
"New York City banned
those kind of floor trusses
based on speculation. And the
city did not rescind that ban."
The NIST investigators
concluded that, instead of
failing, those trusses allowed
the buildings to stand "for a
long time" -- 56 minutes for
the south Tower and 102
minutes for the North Tower.
Long enough for thousands to
escape.
There was no mass
evacuation plan for the towers,
despite the fact that a car
bomb had been detonated in
one of the building's parking
garage in 1993 and it took
several hours to clear the
building of people.
Using computer-generated
effects and expert testimony,
the new film compares what
happened to Oklahoma City's
Alfred P. Murrah Federal
building on April 19, 1995, to
the WTC towers. Over half of
the nine-story OKC building
collapsed in an estimated three
seconds after the bomb's
detonation.
The Murrah building met
the government's strict
standards for construction, but
Timothy McVeigh apparently
parked the truck laden with
ammonium nitrate and fuel oil
at exactly the spot that would
cause the most damage. The
explosion took out three of the
main columns supporting the
transfer girder, which held up
the rest of the building.
It was a "progressive
collapse -- the worst-case
scenario for any structure," the
narrator says in the film.
After 9/11, Corley's team of
investigators from ASCE
recommended mandatory
backup systems, but the codes
were never changed.
The film "Building on
Ground Zero" also focuses on
what improvements may have
been made in the wake of two
federal investigations that
produced 30 proposals to
change building codes.
The answer is none.
The film points out that, five
years after 9/11, the United
States still has no national
guidelines for building tall
buildings.
"(The twin towers) contained
systems that enabled them to
stand for quite a long time,"
said Klein. "The reason I
decided to put the Murrah
Building in (the film) was to
show what happens when you
don't have those systems in
place.
"In fact, if there is a lesson
to be learned about
engineering and construction
after 9/11, it is to build them
like the World Trade Center,"
Klein said.
The documentary also
explores how safe is safe
enough -- and at what price.
It refers to studies by Jake
Pauls, a world authority on
building evacuation, in which
he determined that during the
1993 car-bombing of the WTC,
it took "up to six hours for
people in the upper floors to
get down the emergency stairs
. . . Nearly three times as long
as the fire-protection rating for
the building's steel columns
and trusses."
The costs for increasing
safety are often responsible for
no improvements being made.
Improving fire-proofing on
steel structures can delay or
prevent collapse, but it can
increase construction costs by
5 percent or more.
"I would like the issue of
building safety . . . to be a
positive legacy of 9/11," said
Klein.
"I don't just want to wallow
in the horror and tragedy."
Rita Sherrow 581-8360
rita.sherrow@tulsaworld.com
documentary
“NOVA: BUILDING ON GROUND ZERO”
When
7 p.m. Tuesday
Where
PBS, channel 11
Associated Images:
"Nova" probes the conclusions of the government
engineering investigation into the World Trade
Center’s collapse on 9/11 in "Building on Ground
Zero," airing at 7 p.m. Tuesday on PBS, channel 11
in Tulsa.
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