Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
BUILDING BIG LogoImage with 5 links within the image.
Skyscraper
BUILDING BIG Home Page BUILDING BIG Site Map BUILDING BIG Labs BUILDING BIG Databank BUILDING BIG Glossary
Bridges
Domes
Skyscrapers
Dams
Tunnels
Buy the DVD
_   Citicorp Center
Choose another wonder

Citicorp Center
Click photo
for larger image.
Vital Statistics:
Location: New York, New York, USA
Completion Date: 1977
Cost: $175 million
Height: 915 feet
Stories: 59
Materials: Steel
Facing Materials: Aluminum, reflective glass
Engineer(s): William LeMessurier and Associates

From the very beginning, the Citicorp Center (today, the Citigroup Center) in New York City was an engineering challenge. When planning for the skyscraper began in the early 1970s, the northwest corner of the proposed building site was occupied by St. Peter's Lutheran Church. The church allowed Citicorp to build the skyscraper under one condition: a new church would have to be built on the same corner, with no connection to the Citicorp building and no columns passing through it.

Citicorp Center
Click photo
for larger image.

How did the engineers do it? They set the 59-story tower on four massive columns, positioned at the center of each side, rather than at the corners. This design allowed the northwest corner of the building to cantilever 72 feet over the new church.

In 1978, the skyscraper's chief structural engineer, William LeMessurier, discovered a potentially fatal flaw in the building's design: the skyscraper's bolted joints were too weak to withstand 70-mile-per-hour wind gusts. With hurricane season fast approaching, LeMessurier took no chances. He convinced Citicorp officers to hire a crew of welders to repair the fragile building. For the next three months, a construction crew welded two-inch-thick steel plates over each of the skyscraper's 200 bolted joints, permanently correcting the problem.


Here's how this skyscraper stacks up against the biggest skyscrapers in the world.
(height, in feet)

Chart showing the relative size of the biggest skyscrapers in the world Citicorp Center
915'

Fast Facts:
  • The Citicorp crisis of 1978 was hidden from the public for almost 20 years.
  • The 30-page document outlining the structural mistakes in the Citicorp building was called "Project SERENE." The acronym stands for "Special Engineering Review of Events Nobody Envisioned."
  • Six weeks into Citicorp's repair, a major storm, Hurricane Ella, was off Cape Hatteras and heading for New York. With only half the repairs finished, New York City was hours away from emergency evacuation. Luckily, Ella turned eastward and veered out to sea.
  • Citicorp Center was the first skyscraper in the United States to contain a tuned mass damper, a pendulum-like device that reduces the sway in tall buildings caused by the wind.

  _
_