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Buildings
Ground Zero Engineers Speak
(architecturalrecord.com
- 2/7/02)
By John E. Czarnecki, Assoc. AIA
Key figures involved in the cleanup at Ground
Zero spoke in a panel discussion “From Ground Zero,” at
the National Building Museum in Washington, D.C., January 28. Moderated
by Charles H. Thornton, P.E., chair and managing partner of Thornton-Tomasetti
Group, the panel included Daniel Cuoco, P.E., president and managing
principal of LZA/Thornton-Tomasetti, George J. Tamaro, P.E., partner
with Mueser Rutledge Consulting Engineers, and Ralph W. Johnson,
senior vice president with Turner Construction. The event was cosponsored
by the Associated General Contractors of America and the American
Council of Engineering Companies.
Cuoco noted the services that the structural engineers
have provided at the WTC site:
- emergency damage assessment of buildings in the immediate collapse
area
- identify unstable areas
- develop demolition and temporary stabilization procedures
- identify safe locations for heavy equipment, design reinforcement,
and grillages
- develop and coordinate survey monitoring program
- inspect more than 400 buildings in the area surrounding the collapse
site in a 2-day period (rapid visual assessment)
- detailed investigation of damaged buildings
The panelists, sometimes in amazing detail, described the challenges
in this extraordinary effort while showing slides of the site from
September 11 through January. The following are excepts of Cuoco’s
comments.
Cuoco on the cleanup of the debris that had fallen
on the Winter Garden glass roof adjacent to 3 World Financial Center:
“One of the things we had to do every night and every day
was to remind the contractors that they couldn’t remove the
debris because the Winter Garden roof would fall. At the same time
we were designing temporary shoring that would be able to hold that
up so that they could remove this debris. And then, one day, the
fire department said we’re going to remove this debris in two
days because they felt they had a lot of people in there, possibly
a fire chief. We said that if that debris was out before we put
the shoring in, the Winter Gardens roof was going to fall down.
They said, “well, ok, we can rebuild it again.” The priority
was to try to found people. So in two days we were able to get the
shoring design finished and I shored it and the debris on the Winter
garden roof has all since been removed. Those are the types of things
that we were up against. We had to put the priorities where they
belong.”
Cuoco on obtaining the necessary steel beams to
form a platform for a crane:
“Our first crane challenge was to get a crane between buildings
4 and 5 on the plaza, but there was really no way. This was a 300-ton
crane. There was no way the plaza would support it. Then we realized
there was this granite sculpture that was in there, if any of you
remember between the two buildings and you walk up the steps there
and it was on a thick concrete base. We did some calculations and
we figured out that the thing weighed about 200 tons. And the structure
had been strengthened in that local bay and the columns under it.
So we realized if we could get rid of the sculpture, then we could
put a crane there. We inspected the columns below, and they were
in pretty good shape only needing some minor reinforcing. We needed
to design a grillage that would span over the plaza and land on
those four columns. So we did some calculations and designed some
beams. The contractor called the steel fabricator for eight beams,
and he said, “well, I don’t have those beams.” So
using the beams he had, we came up with some designs, faxed up a
sketch and within two hours they had the steel on the truck on its
way to the site. It’s just incredible. No questions asked.”
Cuoco on using WTC box columns as supports for
a crane:
“One day we got notice that there was an 800-ton crane on
the way to the site, and it had to go right next to the opening
on the slurry wall. We were told that we couldn’t approach
the slurry wall with a crane that heavy. You have to stay 30 feet
away. There’s no way; otherwise you’re going to put pressures
within that 30-foot distance. So, we figured out that if we could
bridge over the 30 feet and put a beam between the slurry wall and
the 30-foot point, we would not put any load on that 30-foot distance.
Of course the vertical load would go onto the slurry wall but that
was insignificant. We did some calculations and there really weren’t
big enough beams in the area to support the crane. So we looked
in the debris pile and we realized that there were some really big
box columns from the core that were 5-feet-by-3-feet, more than
30 feet long, really heavy, and some of them were pretty straight.
We measured them, did some calculations and we were able to use
them as runways for the 800-ton crane.”
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