Day 461

A tower on stilts

April 4th, 2013

From the pages of The New Yorker:

When planning for Citicorp Center [now known as Citigroup Center] began, in the early nineteen-seventies, the site of choice was on the east side of Lexington Avenue between Fifty-third and Fifty-fourth Streets, directly across the street from Citicorp's headquarters. But the northwest corner of that block was occupied by St. Peter's Church, a decaying Gothic structure built in 1905. Since St. Peter's owned the corner, and one of the world's biggest banking corporations wanted the whole block, the church was able to strike a deal that seemed heaven-sent: its old building would be demolished and a new one built as a free-standing part of Citicorp Center.

To clear space for the new church, [the architect and engineer] 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 comer. This daring scheme allowed the designers to cantilever the building's corners seventy-two feet out over the church, on the northwest, and over a plaza on the southwest. The columns also produced high visual drama: a nine-hundred-and-fourteen-foot monolith that seemed all but weightless as it hovered above the street.
In 1978, the year after Citicorp Center was completed, Bill LeMessurier, the project's structural engineer, was reviewing his design and discovered, to his horror, that a perfect storm of factors — an omitted calculation (one not required by the city's building code) on his part, plus two cost-saving shortcuts taken by the construction team (neither of which would have been a problem on its own) — had resulted in the building being highly susceptible to catastrophic collapse if hit by strong diagonal winds.

And it was almost peak hurricane season.

LeMessurier alerted the architect and the Citicorp higher-ups, and they embarked on a secretive plan (known by city officials, but not by the general public) to strengthen the structure's wind braces, bringing in welders every night over the course of two months to fortify more than 200 bolted joints in the building's skeleton, starting with the most critical locations.

If people had found out what was going on, it could have been extremely damaging to the reputations of the bank and the design team, but the media never picked up on the story. The day after Citicorp put out a press release "in language as bland as a loan officer's wardrobe" about the upcoming welding work, the city's papers went on strike, and they didn't resume publication until weeks after the last joint had been fixed. It was only the aforementioned New Yorker article (well worth reading) that finally revealed the tale to the public in 1995.

And as for the building: with its reinforced, welded joints, Citigroup Center is now said to be one of the safest structures ever built.

Leave a Reply