Can the buckling Manhattan skyscraper be saved? Engineers weigh in
As officials continue to investigate the cause, experts say that if the conversion is to proceed, “extensive work” would need to be done to shore up the damage and evaluate the building’s safety and integrity.
Extensive work will need to be done to fortify a 37-floor skyscraper in Midtown Manhattan in which several columns suddenly began buckling this week, prompting an emergency evacuation of nearby offices and street closures.
The building is undergoing renovations, cited as the largest ever office-to-residence conversion in Manhattan. Structural engineering experts said for the project to proceed the building would need comprehensive work to shore up the damage and evaluate the safety and integrity of the skyscraper.
“This sort of failure is highly unusual,” said Jerome F. Hajjar, who is a university distinguished professor and the CDM Smith Professor of Civil and Environmental Engineering.
“We have a lot of steps in our processes that typically prevent this from happening,” Hajjar said, citing the national standards that guide the structural calculations that planners are expected to undertake. One example is the American Society of Civil Engineers’ standard for determining the loads buildings must be designed to withstand, or ASCE/SEI 7.
Located on East 42nd Street, the building, once part of pharmaceutical and biotechnology giant Pfizer’s global headquarters, is in the process of being converted from offices into apartments. On Tuesday, officials ordered an evacuation of the surrounding blocks after responding to a structural issue that they said could lead to a partial collapse of the building.
During a press conference that same day, New York Mayor Zohran Mamdani said that officials arriving at the scene reported structural issues on the 21st floor, including that “two structural columns had buckled, in addition to multiple cracks and sagging floors.” Ahmed Tigani, the city’s building commissioner, said the building had been stabilized later in the day as emergency repairs commenced.
The renovation involved enlarging the former Pfizer headquarters, widening its upper floors to create more than 1,500 planned apartments. The developer told the Wall Street Journal that the work may have imposed additional weight on two columns on the 21st floor, which may not have been adequately reinforced.
Photos by Alyssa Stone/Northeastern University
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But just why the damage impacted only those two columns remains unclear.
The range of potential causes is wide, Hajjar said. It could stem from an issue dating back to the building’s original construction that only became apparent during the renovation. It is possible, he said, that discrepancies between the building as constructed and its original design plans meant parts of the structure were less capable of supporting the additional loads imposed during the renovation.
“It’s really hard to say what causes something like this, and often it’s a combination of things that lead to it,” he said.
Mehrdad Sasani, a professor of civil and environmental engineering at Northeastern University, agreed that such problems are “usually multifaceted.”
Sasani said another possibility is that the renovation team may not have fully understood the strength of the building’s existing steel columns before work began. He said structural engineers should test samples from older buildings to determine the materials’ actual strength rather than relying on dated plans or specifications, not least because the real-world properties of decades-old materials can differ from what is documented.
Hajjar said that during a structural failure like this, the load — the weight the structure is designed to support — often gets redistributed to other parts of the building. “That happens at the time of the failure,” he said.
For the building to have buckled on one floor and then held steady, Sasani said that there are two general mechanisms likely at work in redistributing the load: one is referred to as the catenary action, in which floor beams begin behaving like cables to transfer weight to neighboring columns. The other is the Vierendeel frame action, which describes how the network of beams and columns throughout the building redirects weight to undamaged parts of the structure.
“The basic idea is that once those two columns can no longer carry the load, the weight has to be redistributed through the rest of the structure,” he said. “And it’s not just the floor immediately above: the entire structure above the damaged floor helps redirect that load to other columns that are still intact.”
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Structural engineers have established methods for assessing the integrity of damaged structures, including evaluating how the building’s load has been redistributed, how that might influence other parts of the building and what risks repairs could pose, Hajjar said. Those analyses also include more comprehensive evaluations of the building’s safety in its current condition, he said.
“I appreciate the fact that there are professionals who went out and tried to evaluate the situation, and I’m not in a position to second-guess them,” Hajjar said.
Sasani said he thinks rehabilitating the building is still possible.
“I would start with extensive, continuous monitoring by installing lots of sensors to make sure any movement is detected,” he said.
The floors above the buckled columns would need to be strengthened with temporary supports, diagonal braces and other structural elements so the building can better redistribute the load away from the damaged columns, Sasani said. Then the damaged sections could potentially be removed or repaired, he added.
But even so, Sasani said that work promises to be extensive, requiring careful planning to safely redistribute the building’s load during pinpoint repair work.
