Some of the stairwells were constructed of gypsum
shaftwall, tongue-and-grooved at vertical joints, without
studs, a not uncommon practice.
This shaftwall system is strictly for fire separation, has
little lateral resistance, and its the cheapest way to enclose
a vertical shaft.
Recall that in one case where people were trapped
in an elevator, a worker gnawed through the elevator shaft
wall with a window washing squeegee edge.
Other interesting discoveries and comments:
Britain requires a dedicated elevator in high-rises for
emergency workers, fire protected and reinforced in high-rises,
but that requirement has been opposed by US property owners.
A computer model showed that a plane wing with no fuel
into would not have sheared exterior columns and spandrels,
but with fuel in the wing several columns and spandrels were
punched away.
About one-third of the plane fuel was consumed outside
the buildings in fireballs. The rest of the fuel did not cause
weakening of the steel, that was caused by the higher
heat of furnishings burning with heat increased to by
indrawn air from popped windows which turned the floors
into high-temperature forges. Fuel burning alone would not
have caused the collapse.
NIST said the buildings are likely to have survived the
aircraft impacts if the subsequent fires has not occurred.
Sprinkers were underdesigned for the buildings by about
1/2, although none worked due to disruption of water
supply.
Interior furnishings, workstations in particular, absorbed
a very large proportion of the planes' impact. Studies showed
that without furnishings much of the plane might have gone
all the way through the building, but would have also done
greater damage to the structure.
Both towers collapsed first at locations away from the points
of impact. Furnishings were pushed away from the points of
impact, and fires from their piles, fed by fresh air from popped
windows, weakened structure at those locations and initial
collapse occurred there.
Studies of responders climbing high rises showed that
it takes up to 2 hours (126 Minutes) to reach the top floor
of a 60-story structure.
Escapees using stairwells take longer to get down them
in an emergency than in a non-emergency situation -- as
NIST said, that appears counter-intuitive. Fear, confusion
and indecision of escapees during emergencies appears
to lead to a slowdown.
The Port Authority in today's Times claims the NIST
study is wrong.
shaftwall, tongue-and-grooved at vertical joints, without
studs, a not uncommon practice.
This shaftwall system is strictly for fire separation, has
little lateral resistance, and its the cheapest way to enclose
a vertical shaft.
Recall that in one case where people were trapped
in an elevator, a worker gnawed through the elevator shaft
wall with a window washing squeegee edge.
Other interesting discoveries and comments:
Britain requires a dedicated elevator in high-rises for
emergency workers, fire protected and reinforced in high-rises,
but that requirement has been opposed by US property owners.
A computer model showed that a plane wing with no fuel
into would not have sheared exterior columns and spandrels,
but with fuel in the wing several columns and spandrels were
punched away.
About one-third of the plane fuel was consumed outside
the buildings in fireballs. The rest of the fuel did not cause
weakening of the steel, that was caused by the higher
heat of furnishings burning with heat increased to by
indrawn air from popped windows which turned the floors
into high-temperature forges. Fuel burning alone would not
have caused the collapse.
NIST said the buildings are likely to have survived the
aircraft impacts if the subsequent fires has not occurred.
Sprinkers were underdesigned for the buildings by about
1/2, although none worked due to disruption of water
supply.
Interior furnishings, workstations in particular, absorbed
a very large proportion of the planes' impact. Studies showed
that without furnishings much of the plane might have gone
all the way through the building, but would have also done
greater damage to the structure.
Both towers collapsed first at locations away from the points
of impact. Furnishings were pushed away from the points of
impact, and fires from their piles, fed by fresh air from popped
windows, weakened structure at those locations and initial
collapse occurred there.
Studies of responders climbing high rises showed that
it takes up to 2 hours (126 Minutes) to reach the top floor
of a 60-story structure.
Escapees using stairwells take longer to get down them
in an emergency than in a non-emergency situation -- as
NIST said, that appears counter-intuitive. Fear, confusion
and indecision of escapees during emergencies appears
to lead to a slowdown.
The Port Authority in today's Times claims the NIST
study is wrong.