The Skyscraper That Almost Killed New York

There’s a building standing right now in midtown Manhattan that, for a few terrifying months in 1978, had a very real chance of killing thousands of people.
Not because of a terrorist threat. Not because of a fire. Because of the way it was built.
The Citicorp Center — a sleek, 59-story tower with its famously distinctive slanted top — had been open for less than a year when its own structural engineer discovered that it could collapse in a moderate hurricane. The kind of storm that passes through New York every few decades. Maybe sooner.
Over 200,000 people lived and worked in the surrounding area. Hurricane season was weeks away. And one man had to decide what to do with that information.

It all started with an unusual problem. Back in the 1960s, Citicorp wanted to build a new headquarters in Manhattan, and they’d found the perfect city block — except for one thing. There was a church on it, and the pastor wasn’t budging. St. Peter’s Lutheran Church had been there for generations, and its pastor Ralph Peterson wasn’t about to hand over the land so a bank could put up a skyscraper. His terms were non-negotiable: the church had to remain, it had to be physically distinct from whatever went up around it, and two-thirds of the space above it had to stay completely open.

This created a design puzzle that, under normal circumstances, would have been a headache. But it landed in the hands of structural engineer Bill LeMessurier — and he turned it into something remarkable.
The solution? Build the tower on stilts. Not at the corners, the way virtually every other tall building does it, but at the midpoint of each face. The whole thing would essentially hover, held up by four massive legs positioned like the midpoints of a square, not its corners. An engineer once described it simply: imagine a chair where the legs are in the middle of each side, not at the corners. “Obviously, it’s not an ideal situation,” he noted. “It doesn’t seem very stable.”

That’s putting it mildly. But LeMessurier had a plan.

He sketched the solution on a napkin, as engineers apparently do when they’re onto something big. Six layers of diagonal chevron braces running up each face of the building, channeling forces down through the mid-face stilts instead of corners. It was elegant. It was original. It had never been done before.
He also added something else that was genuinely new to skyscraper design: a tuned mass damper. The building, because of its lightweight chevron structure, was more susceptible to swaying in the wind — not a structural problem, but uncomfortable for the people working in it. LeMessurier solved it by placing a 400-ton concrete block on the top floor, floating on springs, designed to oscillate slightly out of phase with the building’s natural sway. Every time the building leaned one way, the block would push back. It was, by all accounts, brilliant.

“It’s the first tall building in the world ever built with mechanical help to make the structure work. That’s remarkable.”
When Citicorp Center opened in 1977, it was the 11th tallest building in the world. Architects and critics loved it. The American Institute of Architects gave it an honor award. For one shining moment, everything was perfect.

Then a student called.
In the spring of 1978, a structural engineering student was working on a thesis about the Citicorp tower. In the process, someone at LeMessurier’s firm got an inquiry: had the diagonal wind loads — what engineers call “quartering winds,” hitting the corners of the building rather than straight-on — been considered in the original calculations?

The question nagged at LeMessurier. He went back and checked.
What he found was bad. The quartering winds increased the forces on the chevron joints by about 40%. On its own, that might have been manageable. But then he discovered something else: when the building was being constructed, the contractors had swapped the welded brace connections for bolted ones to save money — about a quarter million dollars — and LeMessurier’s firm had signed off on it.
Welds and bolts aren’t inherently different in quality, but the substitution had been made without recalculating for the diagonal wind loads. And bolted connections were weaker under the kind of tension that quartering winds created.

He flew to Canada to have the calculations checked at a wind tunnel facility. The results were worse than he’d thought.
“I think this thing is in real trouble.”
The static analysis showed a 40% increase in stress. The dynamic analysis — accounting for the building actually moving in the wind — showed it could be up to 60% worse. Working joint by joint, floor by floor, LeMessurier found the weakest point: the 30th floor. If those joints failed, the whole building would come down.

The probability of a storm strong enough to cause collapse, averaged over any given year? One in 16. And that was only if the power stayed on and the tuned mass damper kept working. In a blackout, even a modest 110 km/h wind blowing for just five minutes could bring the whole thing down.
One year earlier, before the building even opened, Hurricane Belle had sent gusts exactly that strong through Manhattan.

LeMessurier sat alone with this knowledge for a stretch of time that, by any measure, must have been unbearable. He later admitted to contemplating driving his car into a bridge at high speed. “That would be the end,” he said, “and all of this would go away.”

But there were thousands of lives at stake. So he made a different choice.
He called the architect. Together they told Citicorp’s chairman. Within hours, emergency generators were installed to keep the tuned mass damper running in a blackout. And a secret repair plan was set into motion — first nicknamed Project Pandora, then quickly renamed to the more reassuring-sounding SERENE: Special Engineering Review of Events Nobody Envisioned.
Every night, after the office workers went home, welders would slip into the building, strip back the drywall around the chevron joints, and weld thick steel plates over each connection.

“Like band-aids, literally band-aids on both sides of these joints.”
Then the walls would go back up, the mess cleaned, and by morning no one inside knew anything had happened. Over 200 joints needed reinforcing. LeMessurier ranked them by importance and started with the 30th floor. The repairs needed to be finished before a major hurricane could arrive. They weren’t even close to halfway done when a hurricane started brewing in the Caribbean.

The evacuation plan was ready. Police would go door-to-door across a 10-block radius. But Ella stalled just off the Carolina coast, churned and intensified — and then, at the last minute, veered out to sea. The city never knew how close it had come.
LeMessurier called the morning after Ella turned away “the most beautiful day the world has ever seen.”

The repairs were completed in October 1978. The building, which had a roughly 1-in-67 chance of collapsing over its lifetime before the fix, could now withstand what engineers call a one-in-1,000-year storm. For almost two decades, almost nobody outside a tight inner circle knew any of this had happened.

Then, in 1995, The New Yorker published the story.
Here’s the thing about what followed: LeMessurier wasn’t destroyed. He was celebrated. The engineering world held him up as a model of professional integrity — the engineer who, when faced with a career-ending secret, chose to come clean and fix it rather than bury it and hope for the best. His case is now taught in engineering ethics courses around the world.

The mystery of the student who sparked the whole chain of events took decades to fully unravel. A Princeton student named Diane Hartley had actually been investigating the same quartering wind question for her thesis, but when she raised concerns with LeMessurier’s engineers, she was told it wasn’t an issue and let it go. A man named Lee DeCarolis later came forward to say he’d been the one to actually call LeMessurier. LeMessurier died in 2007, before any of it was fully sorted out.

The tuned mass damper he pioneered at Citicorp has since been copied around the world. Six of the twenty tallest buildings on earth now use them. Taipei 101 has a 660-ton pendulum visible from inside the building — a tourist attraction, now, swaying gently to keep the tower stable against typhoons and earthquakes.
And the Citicorp Center itself was sold in 2001, renamed 601 Lexington, and its official project description doesn’t even mention the repairs. LeMessurier’s old firm never responded to interview requests. The building owner wouldn’t let cameras inside.
Some stories, apparently, are still a little too complicated to be comfortable with.
But the lesson buried inside this one isn’t really about engineering. It’s about what a person does when they discover, alone and in private, that something has gone terribly wrong and they’re responsible. When the easiest path would be to say nothing, when silence might just work, when the alternative is public humiliation and professional ruin.
“If you see something that is a social risk, you must do something. You must do something.”
He did.

The article is based on the video “How a Student’s Question Saved This NYC Skyscraper)”

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