In 1978, William J. LeMessurier, one of the nation's leading structural engineer
s, received a phone call from an engineer
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 cantalever
the building's four corners, allowing room for the church beneath the northwest side. (see the pictures, listed below)
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 brace
s; 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 bolt
s instead of weld
s, 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 built plywood boxes around the joints, so as not to disturb the tenants, who remained largely oblivious to the seriousness of the problem.
"Instead of lawsuit
s 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."
Pictures of the unique Citicorp tower:
Thanks to mkb
for making me find new pics to replace the old ones!
Most of this information came from a New Yorker
article by Joe Morgenstern (published May 29, 1995). This article also appears to have inspired these webpages: http://onlineethics.org/moral/LeMessurier/lem.html and http://www.pbs.org/wgbh/nova/pisa/moncit.html