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CNN Live At Daybreak
America Under Attack: Engineer Gives Perspective on Cause of Twin Tower Collapse
Aired September 14, 2001 - 08:41 ET
THIS IS A RUSH TRANSCRIPT. THIS COPY MAY NOT BE IN ITS FINAL FORM AND MAY BE UPDATED.
THIS IS A RUSH TRANSCRIPT. THIS COPY MAY NOT BE IN ITS FINAL FORM AND MAY BE UPDATED.
PAULA ZAUN, CNN ANCHOR: And joining me now is a man that knows an awful lot about what these heroic Americans are up against in their cleanup efforts and their recovery efforts.
Todd Rittenhouse, welcome.
TODD RITTENHOUSE, STRUCTURAL ENGINEER: Thank you, Paula.
You are a structural engineer.
You were called in to help assess the damage after the World Trade Center bombing and you also were involved with the Oklahoma City bombings.
RITTENHOUSE: That's right. We step in and try to help ascertain what actually happened during the event and how we can we prevent it from happening again.
ZAUN: All right, explain something to me. I am told the World Trade Centers were expected to be able to withstand the brunt of a force of a 707. What happened?
RITTENHOUSE: That's what, apparently, they try to, but in this case there's a much larger jet, it's a 400 thousand pound aircraft approximately, carries a lot of fuel, and it's not only the impact of a much bigger fuel -- bigger plane, but also all the fuel that it was carrying that ignited and damaged the structure.
ZAUN: All right. We're going to look at some pictures now, the pictures that of course will be forever seared into our national consciousness here. What effect did the fuel have on weakening this structure? I can imagine a tremendous amount of heat was put on it?
RITTENHOUSE: Right. Well, there are two parts: first, the aircraft impacting the structure, which does a lot of damage to the structure; then you have the explosion of the fuel afterwards, which then goes to soften and melt the structure that is remaining. That becomes instable and ultimately collapse upon itself. So it's the jet aircraft flying into the building and the huge fireball that ensued afterwards.
ZAUN: Now, aren't these buildings built so they will fall like a tree instead of straight down. RITTENHOUSE: Well, it's one of the -- the way that this occurred, the attack happened at such a high level that it made the top portion of the building instable and that fell down and kind of creating a pancake effect as it went down the structure.
ZAUN: Yes, we're watching that right now. It's hideous to watch.
RITTENHOUSE: Right, it's just -- it is, it's a very sad thing to watch.
ZAUN: So they knew exactly what they were doing. They knew the angle to hit this building at.
RITTENHOUSE: They did a very good job...
ZAUN: They knew where to hit it on the first tower, where to hit it on the second. I mean, they tried that first the time around, right?
RITTENHOUSE: They tried from the...
ZAUN: They tried it from the basement the last time, they wanted the two towers to collapse into each other.
RITTENHOUSE: Correct.
ZAUN: What did they figure out this time that they didn't accomplish the first time.
RITTENHOUSE: Well, the first time they hit it so low...
ZAUN: I am making an assumption I should not be here...
RITTENHOUSE: Right.
ZAUN: ... that the same people were responsible for the first bombing. But you know what I'm saying.
RITTENHOUSE: I understand.
No, the difference is there was a 107 stories above the detonation point in the first attack, and that's a tremendous amount of weight, so the (UNINTELLIGIBLE) is so much larger to overcome that weight that it's carrying.
This time they moved higher into the building, made the building unstable at a higher elevation, where there it's so much load and it's much softer, it's much more softer, that elevation. So they were able to penetrate it, have this huge fireball, damage the structure, and then it will collapse down upon itself like it did.
We're very fortunate it did collapse upon itself because we have huge degree of rubble in one location as opposed to a tree falling, although, which could have taken out more buildings and many, many more people. So we're fortunate in that. ZAUN: But the fact remains that some 100 buildings in the surrounding area have been damaged, and we're getting all kinds of conflicting information about whether any of those will fall.
RITTENHOUSE: That's right.
ZAUN: There's this 54-story tower we're all watching. The mayor came out yesterday and said everybody had reporting prematurely that it was going to go, but acknowledged that there are some structural damages.
RITTENHOUSE: That's right. There are many buildings around the ground zero area that are perhaps unstable, and we're going through right now, there are many individuals, engineer, the Structural Engineering Association of New York is out there, trying to work with the city officials to assess the various buildings. We won't know for a long time the exact condition of each of these buildings. We are trying to determine which ones are safe and which ones are not so that the evacuation efforts and the search and rescue people can do their job.
ZAUN: We have just learned from the "Wall Street Journal" this morning that the New York developer who led the group that bought this 99-year-old lease of this building is determined to rebuild it.
RITTENHOUSE: Right.
ZAUN: If they rebuild it are they going to build it differently?
RITTENHOUSE: They certainly will build it differently. I would like to see them rebuild it as a symbol of New York. I have my personal doubts. But what we do after every event, after the first World Trade Center, after the Oklahoma City event and the others that have occurred, we (UNINTELLIGIBLE) associates with many other firms have gone out and tried to tell them how to redo it again, how to build these buildings so that you don't have this problem again.
ZAUN: Todd Rittenhouse, thank you...
RITTENHOUSE: Thank you very much.
ZAUN: ... for your wealth of information.
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