Engines of Our Ingenuity

No. 2303:
WILLIAM LeMESSURIER

John Lienhard presents guest Andrew Boyd

Today, scientist Andrew Boyd averts disaster. The University of Houston presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

CitiGroup Center Building The building was structurally unsound. Standing fifty-nine stories, it was the seventh largest building in the world when it was finished in 1977. And it had a flaw that could bring it toppling down in strong winds, killing far more people than perished in the World Trade Center by some estimates.

This was Manhattan's new Citicorp Center, and the problem arose a year after it was finished and tenants moved in. Structural engineer William LeMessurier had met city building codes for winds hitting the building broadside but had not accounted for winds at an angle. Angular wind tests weren't required by the city, and he hadn't thought to perform any. A call from a student alerted LeMessurier to the danger. To his credit, LeMessurier didn't brush aside this young, inexperienced voice, but ran his own tests. Sure enough, the student was right.

Here the story really begins: What would LeMessurier do? The obvious answer was, fix the problem. But engineering problems are never black and white. Engineers live in a world of probabilities. No structure could ever be constructed to withstand every possible disaster. Over-engineering can quickly make costs prohibitive. So they design within the limits of acceptable risk. Suppose we expected hundred-mile-an-hour wind only once in a thousand years. Should we design against so unlikely an event?

LeMessurier had to decide whether the new information made the risk serious enough to push the panic button. And he realized that pushing the panic button would almost certainly lead to personal disgrace and the end of his career. LeMessurier was a member of the National Academy of Engineering who described himself as "vain." Could he deal with his own vanity?

After brief agonizing, LeMessurier not only told everyone involved, he also recommended that the weakness could be fixed by welding special metal plates at important joints in the structure. Welded joints were in the original design of the building, but they'd been replaced by much weaker bolts when construction firms bid on the job. The bolts had been well within engineering safety standards -- before the angular wind issue had been uncovered.

For weeks, workers went about the inside of the building at night, tearing down drywall, welding, and patching things up before tenants arrived each morning. It took the coordinated effort of Citibank owners, New York City officials, engineering firms, lawyers, and consultants to carry it off. Permits had to be issued, contracts written, and (until the fixes were made) evacuation plans had to be drawn up in the event of severe weather.

Despite all that, the last welding spark flew a scant four months after that student phone call. Such unimaginable speed attested to both the seriousness of the problem and the resolve of all involved.

As a footnote, a newspaper reporters' strike coincided with the event, and it didn't get full coverage until the New Yorker published an extensive article seventeen years later. As for LeMessurier? Not only did his career survive -- he became a folk hero. And why not! To quickly admit and repair an error -- that seems to've become a rare and wonderful thing for any public figure.

I'm Andy Boyd, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


Dr. Andrew Boyd is Chief Scientist and Senior Vice President at PROS, a provider of provider of pricing and revenue optimization solutions. Dr. Boyd received his A.B. with Honors at Oberlin College with majors in Mathematics and Economics in 1981, and his Ph.D. in Operations Research from MIT in 1987. Prior to joining PROS, he enjoyed a successful ten year career as a university professor. His new book is, The Future of Pricing: How Airline Ticket Pricing Has Inspired a Revolution, (New York: Palgrave-MacMillan, 2007).

J. Morgenstern, The Fifty-Nine Story Crisis. The New Yorker, May 29, 1995, pp. 45-53.

William LeMessurier, 81, Structural Engineer. Obituary, The New York Times, June 21, 2007. pg. C13.


CitiGroup Center Building
(Images courtesy of Wikipedia)


The Engines of Our Ingenuity is Copyright © 1988-2006 by John H. Lienhard.