In 1978, William J. LeMessurier, one of the nation's leading structural engineers, received a phone call from an engineering student in New Jersey. The young man was tasked with writing a paper about the unique design of the Citicorp tower in New York. The building's dramatic design was necessitated by the placement of a church. Rather than tear down the church, the designers, Hugh Stubbins and Bill LeMessurier, set their fifty-nine-story tower on four massive, nine-story-high stilts, and positioned them at the center of each side rather than at each corner. This daring scheme allowed the designers to cantilever the building's four corners, allowing room for the church beneath the northwest side.
Thanks to the prodding of the student (whose name was lost in the swirl of subsequent events), LeMessurier discovered a subtle conceptual error in the design of the building's wind braces; they were unusually sensitive to certain kinds of winds known as quartering winds. This alone wasn't cause for worry, as the wind braces would absorb the extra load under normal circumstances. But the circumstances were not normal. Apparently, there had been a crucial change during their manufacture (the braces were fastened together with bolts instead of welds, as welds are generally considered to be stronger than necessary and overly expensive; furthermore the contractors had interpreted the New York building code in such a way as to exempt many of the tower's diagonal braces from loadbearing calculations, so they had used far too few bolts.) which multiplied the strain produced by quartering winds. Statistically, the possibility of a storm severe enough to tear the joint apart was once every sixteen years (what meteorologists call a sixteen year storm). This was alarmingly frequent. To further complicate matters, hurricane season was fast approaching.
The potential for a complete catastrophic failure was there, and because the building was located in Manhattan, the danger applied to nearly the entire city. The fall of the Citicorp building would likely cause a domino effect, wreaking a devestating toll of destruction in New York.
The story of this oversight, though amazing, is dwarfed by the series of events that led to the building's eventual structural integrity. To avert disaster, LeMessurier quickly and bravely blew the whistle - on himself. LeMessurier and other experts immediately drew up a plan in which workers would reinforce the joints by welding heavy steel plates over them.
Astonishingly, just after Citicorp issued a bland and uninformative press release, all of the major newspapers in New York went on strike. This fortuitous turn of events allowed Citicorp to save face and avoid any potential embarrassment. Construction began immediately, with builders and welders working from 5 p.m. until 4 a.m. to apply the steel "band-aids" to the ailing joints. They build plywood boxes around the joints, so as not to disturb the tenants, who remained largely oblivious to the seriousness of the problem.
Instead of lawsuits and public panic, the Citicorp crisis was met with efficient teamwork and a swift solution. In the end, LeMessurier's reputation was enhanced for his courageous honesty, and the story of Citicorp's building is now a textbook example of how to respond to a high-profile, potentially disastrous problem.
Most of this information came from a New Yorker article by Joe Morgenstern (published May 29, 1995) . It's a fascinating story, and I found myself thinking about it during the tragedies of September 11. What if those towers had toppled over in Manhattan? Fortunately, the WTC towers were extremely well designed - they didn't even noticeably rock when the planes hit - and when they did come down, they collapsed in on themselves. They would still be standing today too, if it wasn't for the intense heat that weakened the steel supports.