How did Bill Lameasure discover the building's flaw?

Lameasure discovered the flaw after a student called him with questions about the building's design. This prompted Lameasure to re-examine his calculations, particularly considering 'quartering winds,' which revealed the underestimation of stress on the bolted connections.

What is a Tuned Mass Damper (TMD) and how does it work?

A Tuned Mass Damper is a device, often a large mass on springs or a pendulum, used in tall buildings to counteract sway caused by wind. It oscillates out of phase with the building, absorbing and dissipating kinetic energy, thereby stabilizing the structure and improving comfort for occupants.

How were the structural issues in City Corp Center fixed?

Lameasure initiated 'Project Serene,' a confidential repair operation. Welders reinforced over 200 critical joints on the chevron beams with steel plates, essentially acting like 'band-aids,' prioritizing the 30th floor where stresses were highest.

Was the public aware of the potential danger at City Corp Center?

No, to prevent mass panic, the dangerous flaw and the subsequent repairs were kept secret from the public and most building occupants. Emergency generators were installed for the TMD, and strain gauges monitored the building's stress, with evacuation plans in place as a last resort.

Who was the student who alerted Lameasure to the potential problem?

The identity of the student is debated. While Diane Hartley, a Princeton student, had concerns during her thesis, a man named Lee Dear Carolis eventually came forward claiming to be the student who spoke with Lameasure. Lameasure passed away before confirming the identity.

What is the lasting impact of the City Corp Center incident?

The incident led to updated building codes requiring 'quartering wind' calculations for skyscrapers. Lameasure's actions are lauded as a prime example of engineering ethics. The use of Tuned Mass Dampers, initially controversial, is now widespread globally in tall building design.

How a Student's Question Saved This NYC Skyscraper

Veritasium

Education3 min read34 min video

Apr 26, 2025|23,775,835 views|413,445|21,151

veritasium science physics Veritasium engineering Citicorp building citicorp tower citicorp tower design flaw citicorp center citicorp center saved by student skyscraper skyscraper design

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Key Moments

TL;DR

A student's question exposed a flaw in Citicorp Center, nearly causing its collapse and leading to a massive, secret repair.

Key Insights

The Citicorp Center's unique design, with its 'stilts' and diagonal bracing, created a hidden vulnerability to certain wind conditions.

A student's inquiry prompted structural engineer Bill Lameasure to re-examine his calculations, uncovering a critical flaw regarding quartering winds.

The structural flaw involved insufficient bolts at critical joints, which would have failed under specific wind loads, potentially causing collapse.

Lameasure initiated a covert, high-pressure repair operation ('Project Serene') just before hurricane season to fix the building's vulnerabilities.

The crisis was averted by strengthening critical joints with welds and utilizing the tuned mass damper as a crucial safety measure.

The incident highlights the importance of ethical responsibility in engineering, thorough analysis, and the unforeseen impact of seemingly minor details.

THE AMBITIOUS VISION AND UNFORESEEN CHALLENGE

In the 1960s, Citicorp aimed to build a new headquarters in Manhattan, but a unique constraint emerged: a church on the desired block refused to relocate. The agreement required the new tower to be built around the church, leaving a significant open space. This led architect Hugh Stubbins and structural engineer Bill Lameasure to design a skyscraper on 'stilts'—four central columns supporting the building's gravity and wind loads, a departure from conventional corner supports.

INGENIOUS DESIGN AND EXTERNAL FORCES

To manage gravity loads and wind forces with the stilted design, Lameasure incorporated chevron bracing on each face of the tower, directing forces to the central columns. He also introduced a tuned mass damper (TMD), a 400-ton concrete block on the top floor, to counteract swaying. This innovative system, while saving weight and cost, was initially focused on comfort and structural integrity under known conditions.

THE CRITICAL FLAW REVEALED BY A STUDENT

In the summer of 1978, less than a year after opening, Lameasure learned that the crucial welded braces had been replaced with bolted connections to save costs. A few weeks later, a student's question about the building's design led Lameasure to re-evaluate wind loads, specifically under 'quartering winds' (hitting a corner). His recalculations revealed that these winds would induce far greater stresses than previously considered.

THE SHOCKING DISCOVERY OF THE WEAKNESS

Lameasure's revised analysis showed that the bolted connections, particularly on the 30th floor, were severely inadequate. The forces from quartering winds could increase stress by up to 60%, far exceeding the capacity of the four bolts used at critical joints. The building was in imminent danger of collapse, especially if the tuned mass damper lost power during a storm.

AN EMERGENCY REPAIR OPERATION UNDER THE RADAR

Faced with a terrifying probability of collapse, Lameasure initiated 'Project Serene,' a covert operation to reinforce the building. Welders worked nightly for six weeks, adding steel plates to over 200 critical joints, prioritizing those on the 30th floor. Simultaneously, evacuation plans were developed, and emergency generators were installed for the TMD, all while officials withheld information to prevent public panic.

THE CLOSE CALL AND LASTING LEGACY

Just as repairs neared completion, Hurricane Ella threatened New York. The storm's last-minute diversion saved the city, and the repairs were finished without public knowledge. The incident led to updated building codes requiring quartering wind analysis and established the tuned mass damper as a standard feature in tall buildings worldwide. Lameasure became a symbol of engineering ethics for his responsible actions.

THE MYSTERY OF THE INFORMANT STUDENT

The identity of the student whose crucial phone call alerted Lameasure remained a mystery for years. While a student named Diane Hartley conducted relevant research, and another student, Lee DeCarolis, later claimed to be the caller, Lameasure passed away before definitively confirming the source, leaving a lingering question about who precisely triggered the alarm.

Mentioned in This Episode

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●People Referenced

Ethical Engineering: Key Considerations

Practical takeaways from this episode

Do This

Prioritize public safety above all else.

Thoroughly review all design calculations and assumptions.

Investigate any discrepancies or 'peculiar things' about a structure.

Consult with experts and utilize advanced testing methods (e.g., wind tunnels) when necessary.

Communicate critical issues honestly and promptly to relevant stakeholders.

Implement robust monitoring systems for critical structures.

Own up to mistakes and take decisive action to rectify them.

Update building codes based on lessons learned from engineering challenges.

Avoid This

Do not stay silent about potential structural failures that endanger public life.

Do not rely solely on original calculations without re-verification, especially when changes are made.

Do not underestimate the impact of seemingly minor deviations (e.g., bolts vs. welds) or different wind conditions (quartering winds).

Do not ignore advice from students or junior engineers if it raises valid concerns.

Do not prioritize cost savings over critical safety measures.

Do not withhold information that could prevent a disaster.

Bolt Requirements for Chevron Braces (30th Floor example)

Data extracted from this episode

Condition	Gravity Load (tons)	Wind Load (tons)	Tension (tons)	Required Bolts (approx.)
Perpendicular Wind + Original Gravity Load	340	454	114	4
Quartering Winds + Original Gravity Load	340	635	295	10-11
Quartering Winds + Underestimated Gravity Load (75%)	255	635	380	14

Common Questions

The City Corp Center had a critical design flaw where the chevron bracing connections, originally intended to be fully welded, were substituted with bolts. This weakened the structure's ability to withstand 'quartering winds' (winds hitting the building's corners) which could cause stresses up to 60% higher than anticipated, potentially leading to collapse.

Topics

Structural Engineering Skyscraper Design Wind Loads Building Safety Engineering Ethics Tuned Mass Damper Structural Failure Disaster Prevention Historical Engineering Building Codes

Mentioned in this video

personWalter Rriston

The chairman of City Corp who was informed of the structural flaw and the emergency repair plan.

eventHurricane Ella

A major hurricane that threatened New York City during the 'Project Serene' repairs, causing significant anxiety but ultimately veering away.

productCity Corp Center

The skyscraper at the center of the story, which was discovered to have a potentially fatal structural flaw.

personBill LaMeasure

The structural engineer who discovered the fatal flaw in the City Corp Center and orchestrated the confidential repairs.

personRalph Peterson

The pastor of St. Peters church who negotiated the terms for City Corp's development on the block, ensuring the church's continued presence and independence.

personHugh Stubbins

The architect hired to design the City Corp Center and the new church, facing constraints that led to innovative structural solutions.

eventHurricane Bell

A hurricane that passed through New York City the year before City Corp was completed, whose winds were a precursor to the later identified risks.

tooltuned mass damper

A device designed to reduce the sway of buildings, adopted by Lameasure for the City Corp Center, consisting of a large mass that oscillates out of phase with the building.

personAlan Davenport

An expert at the boundary layer wind tunnel in Canada with whom Lameasure consulted to verify his calculations regarding the building's structural integrity.

organizationColumbia Space Initiative

A student team that helped build a demonstration of a tuned mass damper system for the Veritasium video.

conceptProject Pandora

The initial, ominous name Lameasure gave to the confidential repair plan for the City Corp Center before renaming it Project Serene.

conceptProject Serene

The renamed confidential repair plan for the City Corp Center, chosen to sound less ominous than its original name, Project Pandora.

softwareSy

A service providing affordable global data connectivity, sponsored in the video for its utility in staying connected while traveling.

personDiane Hartley

An undergraduate structural engineering student at Princeton whose thesis work on the City Corp tower involved reviewing documentation and raising early questions about quartering winds.

organizationNational Institute of Standards and Technology

An organization that conducted a study in 2021 to assess if quartering winds posed greater demands on buildings like City Corp.

toolTaipei 101