World Trade Center Design Flaws

Synopsis by: Chris Salvano, Sonoma State University

Among the more shocking images of September 11th was the sight of the
World Trade Centers collapsing into rubble in a matter of seconds.  Why did
both towers of the World Trade Center, set afire in their upper floors,
collapse to the earth?  San Francisco architect and welder Jim Malott
explains his assessment of intrinsic design and construction flaws of the
towers which hastened their complete collapse.

Malott holds a bachelor's degree in pre-architecture from Stanford, a
master's degree in architecture from the Harvard Graduate School of Design.
Malott has studied the properties of steel-reinforced concrete from graduate
courses at the University of Delaware.  He is also a skilled welder and a
practicing architect in the San Francisco area, where he has helped design a
number of high-rise buildings.  Malott has also chronicled and photographed
the towers' birth from the mid-60's to its rise and construction in the
70's.

According to Malott, before the advent of the World Trade Center towers,
high-rise buildings shared two vital characteristics:  one, they were
supported by a grid of steel columns, and two, the columns were encased in a
tough cladding of reinforced concrete.  This concrete created a fireproof
skin designed to withstand a four-hour inferno.  (The four-hour rating is a
building industry standard for fireproofing)  As designed by architect
Minoru Yamasaki the Twin Towers incorporated neither of these traditional
features.  These features were found in most tall buildings before the Twin
Towers came along and changed the equation.  Malott claims that it was the
failure to use the traditional steel column grid design and concrete coating
on the steel columns that was the fatal flaw of the buildings--not the
initial crashes, not the exploding jet fuel and not the subsequent fire
alone.

In an attempt to cut weight--which is the enemy of all high-rise
buildings--the designers of the Towers eliminated the traditional steel
column grid.  Instead, Yamasaki placed the steel columns in the perimeter of
the outer walls of the buildings and in the perimeter of the small inner
core of the buildings that housed the elevator shafts.  This design allowed
every floor to have unobstructed floor space with no interior supporting
columns or beams.

In further attempts to save weight, time and money designers were allowedto
fireproof the steel columns with spray-on mineral-wool fiber and layers of
sheetrock instead of the traditional method of using reinforced concrete.
The elevator shaft and the steel columns in those shaft walls were covered
with sheetrock as well.

Yamasaki and his engineers had indeed calculated the impact of a commercial
jetliner shearing into the World Trade Center.  Even a jetliner flying at
300 mph isn't an overwhelmingly heavy load according to Malott.  The mass of
a 767 aircraft is less than half the mass of one floor of the building.
What wasn't calculated says Malott was a commercial jetliner shearing into
the World Trade Center and stripping the sheetrock fireproofing off the
steel columns and the elevator shaft.  "The culprit was not the jet fuel,"
which Malott has so often reiterated in the wake of the disaster.  "I say
that as a formal naval officer who witnessed a number of catastrophic
aircraft accidents.  Jet fuel vaporizes and ignites instantly.  The real
culprit was that all the fireproofing was blown off on impact."  And since
the Towers didn't have supporting columns and beams, the unobstructed floors
allowed the bodies of the planes to crash into the elevator shaft core.
This in turn destroyed the shaft walls, its fireproof sheetrock and any hope
that the building would survive a four-hour fire.  The exposed steel
immediately became vulnerable to structural failure and it took less than
one hour to heat the unprotected steel to the failure point.

Malott also notes the questionable quality control of some of the welding
in the buildings.  Malott noted that during construction in the 70's each
exterior column section was bolted temporarily, three in a row, then later
welded in place.  Photos after the collapse showed that dozens, perhaps
hundreds, of these welds failed.  The columns fell three in a row, just as
they had been built.  "All of these decisions made back in the 60's were the
precursor of this tragedy," claims Malott.

Malott explains that designers must return to cladding their steel columns
with reinforced concrete or some other tough substitute rather than fragile
sheetrock.  Ever since the World Trade Center pushed the limits of design,
most high-rise buildings in America have followed its lead.  Most wrap their
steel columns in some combination of mineral wool or gypsum board rather
than concrete.  This leaves many of these buildings potentially susceptible
to the same type of structural failure.


Peter Phillips Ph.D.
Sociology Department/Project Censored
Sonoma State University
http://www.projectcensored.org/