DATE October 16, 2001 ACCOUNT NUMBER N/A
TIME 12:00 Noon-1:00 PM AUDIENCE N/A
PROGRAM Fresh Air
Interview: Hassan Astaneh discusses studying the remains of the
World Trade Center
TERRY GROSS, host:
This is FRESH AIR. I'm Terry Gross.
My guest is doing what has been described as an autopsy of the World Trade
Center. Hassan Astaneh is a structural engineer who's being funded by the
National Science Foundation to study the remains of the towers. He's
examining the twisted and bent steel to analyze the building's strengths and
vulnerabilities at the time of the attack and learn lessons we can apply to
protecting future skyscrapers from terrorist attacks. Astaneh is part of a
team investigation organized by the American Society of Civil Engineers. He's
a professor of structural engineering at the University of California at
Berkeley and has inspected many buildings in cities devastated by earthquakes.
One of the most important clues he's discovered in his World Trade Center
investigation is an internal column that looks like it was hit by the engine
of the plane. I asked him what he can deduce from this evidence.
Professor HASSAN ASTANEH (UC-Berkeley): There were two theories. Some people
thought the plane was so strong, so fast it broke the inside columns and just
collapsed them. The other theory was, no, columns were so strong that the
plane hitting them broke apart and just disintegrated. It turns out that at
least in this one case that they have discovered that none of them are true.
What happened here was the engine is the heaviest part of the plane and that
is the one that causes damage. The engine has hit the column, has taken a
chunk of it, kind of like half cylinder out of the side of the column and
gone, but the column or what is left of it was enough to support the floors
and the column was still standing after even losing 40 percent of its capacity
because part of it was taken away with the engine hitting. So there is a
third option here that happen, and that is plane hit the column, took a piece
of it with it but the column was still strong enough to hold the floors.
GROSS: What's another clue that you've found so far?
Prof. ASTANEH: One of the most important things I have found is that the
design of this building certainly was just monumental. It's amazing what kind
of innovations they have introduced to this building. And also construction
of this building, these structures, was almost perfect. For example, all
welds--welds are where we kind of weld two pieces of steel and make connection
and build the structure. So these welds, all of them were ultrasonically
tested. Now even now we don't do it to our structures, on this very critical
structure like nuclear power plant or other structures. So this building in
the early '70s and late '60s, all welds were ultrasonically tested. And that
certainly shows up in my studies, that none of the welds have broken, even
after dropping from elevation of 1,000 feet. It's amazing. The almost
perfect structural design and almost perfect construction was perhaps the
reason, in addition to the fact that the structure was designed for a 707 hit,
was the reason why the structure withstood the impact. It did not have much
damage due to impact. What happened was one hour later, of course, jet fuel
burning that intensely collapsed it. But that one hour was enough to save
maybe 25,000 people.
GROSS: You say the building was designed for a hit by a 707 jet?
Prof. ASTANEH: Yes, that's correct. In fact, Dr. Robertson, who's a
designer of this building, structural engineer of this building, was telling
me that when he was designing this building, he had to actually kind of put
aside a lot of design codes of the city of New York because they were not
enough for such an important structure. So he had to go to the city and
negotiate the fact that this tall building is located between two very busy
airports, there is a possibility that there'll be accidental off-track flight
of planes into this building. He wasn't thinking of terrorist attack in those
days, 1960s, but he was thinking that some plane during fog period might hit
the building. So at that time, 707 was the largest that he thought should be
designed, and he designed the building to withstand impact of 707. Of course,
fire was another story. He did not design certainly for thousands of gallons
of fuel being put inside the building.
GROSS: Have you found any strange things in going through the steel from the
collapsed towers, strange things that don't necessarily relate to what you're
looking for but are very interesting nonetheless?
Prof. ASTANEH: One of the things I'm looking actually--I'm not just looking
at the towers. There is another building in the complex called Building
Seven, which is 47-story building. We call it kind of garden variety building
because we have perhaps 100 of those buildings that like one, 47-story or in
that category. These are part of the family of structures and they are
designed following certain rules, so, in fact, that Building Seven is very
important to me and profession to learn from because the lessons of that
47-story kind of directly apply to a large family of our structures.
That building had come through very, very intense fire in a way that some of
the pieces that I have seen--in fact, the steel--this is almost--for me it was
unimaginable. Some of the steel that was like 5/8ths of an inch thick, that
is evaporated. It's like you see ice on the lakes during spring when the
weather is getting warm and then the ice gets thinner and thinner and
gradually it's kind of disintegrated and it becomes liquid. It's like that.
It's like paper thin and most of it is gone and rest of it is reduced to
almost paper-thin thickness. That is amazing to me. I haven't seen anything
like that. I'm not in fire engineering, but I haven't heard anything like
this, that fire actually can evaporate steel that much.
We still don't know what happened to that structure because that structure was
not hit by the plane. Some people say some of the debris fell on it. But I
feel that there was very intense fire that does not justify to be the result
of paper burning, because these offices have a lot of copies and papers on
files. But the intense fire collapsed that building, and it's not clear what
was the fuel for that kind of fire.
GROSS: Are you suggesting that something happened in Building Seven that we
don't yet know about?
Prof. ASTANEH: Yes. I don't know what happened, but perhaps piece of a
wing--it's pure speculation on my part, because I haven't been able to put
things together yet. These are just pieces of puzzle that I'm putting
together now. But my speculation is that perhaps a piece of wing, which
really contains the jet fuel, fell on this thing. Maybe one of the wings of
one of the planes fell on this or half a wing, just fell on this building from
height of 1,000 feet to about 500 feet, so there was a 500-feet drop of that
wing, and upon impact, it may have ignited a fire or just dumping the fuel
from the roof all the way down, and this was burning because of that fuel.
But that is pure speculation. I don't know. But somehow we have to figure
out what caused the collapse of this building first, and what was the source
of that fire that caused this collapse?
GROSS: What temperature does steel have to get to before it melts?
Prof. ASTANEH: Well, the melting temperature's pretty high, but you don't
need to get to that temperature of 2,500 or more. What happens to steel is
when you get to about 1,000 degrees temperature Fahrenheit, the steel loses
its capacity to carry the load. It's a critical temperature. It's
like--imagine you have ice and water. They're the same material, it's the
temperature that makes water ice, right? So when you start warming up ice,
you don't need to melt ice to lose strength. At certain temperature ice is
actually very soft before it melts. So steel is the same crystalline
material. When you heat up the steel to 1,000 degrees, at that point steel
loses its capacity to carry load. If you continue heating it up, eventually
you make it liquid, but that's not concern for structural engineering
community. Our concern is that critical temperature of about 900, 1,000
GROSS: So you think that only a fire with, say, jet fuel on it could burn
Prof. ASTANEH: Yes. Certainly--what you have is--usually in these
structures you have fireproofing, and many, many years of research and
development we have information that we know how we can protect steel
structures from reaching that 1,000 degrees. Because if there is temperatures
of 1,000 degrees, then everything's over. You shouldn't expect structures
standing. It will collapse on the gravity load. What we have done is we have
come up with these kind of--what's called ratings. All buildings have a
rating. Most buildings have two Rs rating. What it means in terms of, you
know, what it actually is, all buildings have a possibility of catching fire,
right? And these fires usually are due to papers in the building or furniture
or carpet. Those are called kind of office fires.
What we do is we put enough fireproofing on the columns of the steel and
material that if there is a fire and if it lasts two hours even, the steel in
that floor is not going to reach 1,000 degrees. So during that two-hour
period you can either evacuate people and everyone gets out of the building,
or you can bring firefighters and water, or a sprinkler system works and
eventually in two hours you can save people and extinguish the fire, or
actually, everything will burn out anyway. I mean, there is not much in
offices and furnitures and homes that can burn for two hours.
But this was different. You have here tens of thousands of jet fuel, which is
the worst burning--I mean, the most intense burning fuel. That's the way they
have refined it to make sure that per weight it has much more energy because
you are using it in the plane. You won't have the intense fire for the same
weight of fuel. So it's much, much more intense fire for jet fuel than your
car gas. So you bring that kind of fuel and put it inside the building, of
course no fireproofing can last that intense heat.
GROSS: As catastrophic as the collapse of the World Trade Center towers was,
it could have been a lot worse. The buildings could have fallen sideways and
crushed many of the buildings in their paths. Instead, they almost fell as if
it was a controlled demolition. They fell pretty straight down. What was it
about the structure that controlled the fall like that?
Prof. ASTANEH: Well, I also agree with you. I think no one knows what these
criminals had in mind when they decided to do this act of murder. But what I
saw from the way planes hit, if you notice--in fact, one plane hit from one
side in a way that if the tower that it hit had tilted over, which I think
that is what they were expecting, because they hit it from outside in a way
that the north tower will hit the south tower, and the other plane came
actually opposite, hitting the south tower to collapse it on the north tower,
hopefully having both of them going down on Wall Street, which would have
caused immediate collapse, first of all, like Oklahoma City building. There
was no time for people to escape. But also, the whole length of building,
1,300 feet, toppling sideways, dropping on the blocks of Wall Street area, you
can imagine the extent of fire and damage and casualties, perhaps in hundreds
But the building stood, so when they hit the building, it wasn't the impact
that toppled them. They stood. Unfortunately, the fire toppled--basically
collapsed. And then the nature of the structure was that--one of the
innovations was this structure used tube system. In other words, the whole
structure is like a pipe coming up out of the ground. Now if you have
something like that, if you have a pipe which is your structure, if you shoot
that pipe with a bullet and create a bullet hole in that pipe, that pipe is
not gonna collapse. It just has the bullet hole on the side. You cannot
collapse tubes by just one hole.
In fact, this structure has about perhaps 60 columns on each side which makes
the tube, these very closely spaced columns. So even plane and the wings
hitting about perhaps 10 to 15 columns and breaking them, it does nothing
because you still had more than 200 columns standing, even though we lost
maybe 10 percent of columns or so, but 90 percent of columns were in tact, and
they carried the load. Until you actually heated up all of them and all of
them lost strength at one floor--and the top floor collapsed on the bottom
part and you had the catastrophic kind of cascading collapse.
So the most important thing about the structure was that this is perhaps the
only structure that had columns, which are the vertical elements outside the
building, spaced every three feet. No other building has this kind of close
spacing of columns. Usually columns are spaced every 10 feet, but this
structure, because of its importance, the designer, Dr. Robertson, had
decided that we are going to have very stiff structure. Because it's not just
the strength, you have to make your structure stiff also, so if you hit it,
it doesn't bend too much. Otherwise it topples. In fact, the structure's
basically columns, and spaced between the columns are windows, those 22-inch
wide windows. That's why the structures looked so strange when you looked at
it. So the innovation here was really to use a very, very stiff, strong tube
to make sure that the structure can withstand really lateral
forces--hurricane, planes, earthquakes--so it was designed into the system not
to topple, not to be toppled by lateral load.
GROSS: Hassan Astaneh is a professor of structural engineering at the
University of California at Berkeley. He's analyzing the remains of the World
Trade Center towers.
We're going to take a short break here to ask you to support your station so
it can continue to bring you news, analysis, interviews and commentary at a
time when we need it more than ever.
(Soundbite of music)
GROSS: My guest is structural engineer Hassan Astaneh. He's analyzing the
remains of the World Trade Center towers.
What are some of your recommendations for the building of new skyscrapers
based on the lessons that you've learned from the World Trade Center?
Prof. ASTANEH: I feel that what we should do is we should prevent planes
from getting that easily inside the building and delivering the fuel. Now one
of the ways is what we are doing here at UC-Berkeley, and I've been working on
this project for a couple of years. Now it becomes quite applicable to this
case. That is, we are testing and developing certain walls that are made of
steel plates, such as they used in this World Trade Center, but in addition to
that, we are adding a concrete wall behind that steel wall, so it is two walls
together. It's kind of steel and concrete, and they are bolted to each other.
So this kind of system used on the facade of high-rise buildings can prevent
planes from getting inside the building that easily as they did in the case of
World Trade Center and that intact. There will be a struggle between the
plane and such a wall, and the struggle may result, if you design it right, in
a way the plane will disintegrate outside the building. So with that premise,
then we can avoid complete delivery of jet fuel inside the building and
provide protection for a building.
GROSS: Is there a downside to the concrete reinforcement? I mean, it would
make the building much heavier, not to mention more expensive.
Prof. ASTANEH: Well, certainly every time you come up with a solution, you
have to look at the effect on other things. But this concrete can be
lightweight concrete, and it's all constant thickness, so it's not just coming
down as you have the high-rise building and becoming thicker and thicker.
It's only six inches of lightweight concrete, but the gain that you make out
of it is enormous. But as far as construction, it's really simple. That's
why we bolt it. You can cast these concrete walls somewhere else and just
transport it overnight to the site and pick them up and bolt them to the wall.
It's very, very construction friendly. It may add 1 percent to the cost
perhaps, even less--I mean, less than 1 percent to the cost, and
construction-wise it doesn't add much more to the time of construction, but
the gain you make is very large.
GROSS: What was the situation of ground zero when you arrived on the scene to
do your detective work?
Prof. ASTANEH: First time I went there--in fact, I didn't step on a lot
actually that has the bodies. I just stayed at the gate where beyond that
really you enter the place where rescue workers are working, and it was just
different thing than anything I've experienced. I just stood there. I just
said my prayers and respect. And I didn't do any investigation, of course.
It was just totally different world. It was just huge number of people moving
and cranes and trucks, but no one was speaking. It was just like robots from
a silent movie era. It was just totally different, horrifying experience.
And, of course, you know, when you are there, it's total different than what
you see on television from long distance. The smell, the view around it that
is all best of structures of New York surrounding this place, and in the
middle of it suddenly you are seeing like atomic bomb is dropped at this
place. The sense of loss, even now that I'm talking about it, my body just
kind of gets different feeling. It's just totally unexplainable. I
cannot--my English is not strong enough and good enough to explain what I
GROSS: Have there been any human remains in the metal that you're looking at?
Prof. ASTANEH: No, not at all. Absolutely. The time that I've gotten
closest to human belongings--not human remains, of course--was when I saw one
of the kind of lenses of someone's eyeglass, very similar to my eyeglass, you
know, embedded in the concrete of one of these beams that I was looking at.
And that was a time that I was looking at the beams when they were coming out
of the site, not at recycling plant. At recycling plant, they are washed and
cleaned. But when I was looking at it, as soon as I saw this lens of a
glass--in fact, I was with National Guard and police who are there. This is
the restricted area that I was working, so we were kind of like a group of
truck drivers and National Guard people and police and recycling and recovery
people. And all of us just kind of froze when I showed them that there is
this lens, and that was the closest I got to human belongings.
But that was enough even to make you emotional because in the middle of all
this you suddenly realize someone was behind this lens doing the things that
we do every day, like this one and other things. So that was pretty
emotional. It was strong enough for me. I didn't need to see human remains.
That was just good enough--or bad enough for me to feel the depth of sorrow.
GROSS: Well, I wish you good luck with the investigation and I thank you very
much for talking with us.
Prof. ASTANEH: Thank you very much.
GROSS: Hassan Astaneh is a professor of structural engineering at the
University of California at Berkeley. He's analyzing the remains of the World
Trade Center towers. I'm Terry Gross and this is FRESH AIR.
(Soundbite of music)
GROSS: Dan Zanes used to be the lead singer of the indie rock band The Del
Fuegos, but now he performs and records music for kids. Coming up, he
performs some of the songs that have been getting the best response since
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