Unformatted text preview: J. LeMessurier (pronounced "La Measure") in the
early 1970s. Making room for the St. Peter's church was a difficult
problem, but LeMessurier was a highly capable and creative
engineer. His design called for the building to sit atop nine-storyengineer.
tall stilts, one centered on each side with a specific geometry in
the structure's framing to take maximum advantage of the oddly
placed support columns. It also had a single, narrower column in
the center which housed the building's elevator banks and
provided additional strength to the framing. This design made
room for the church under the building's northwest corner, and
gave the giant structure a graceful, almost levitating effect.
gave LeMessurier first became aware of the building's weakness in 1978, about
a year after its completion. An engineering student contacted him to ask
some technical questions about the design, which he was delighted to
address. The student's professor had expressed doubts regarding the
strength of a stilted skyscraper where the support columns were not on
the corners. "Listen, I want you to tell your teacher that he doesn't know
what the hell he's talking about," LeMessurier told the student, "because
he doesn't know the problem that had to be solved." He went on to
explain how the building's framing geometry worked perfectly with the
stilts in such positions, allowing it to withstand very forceful winds, even
from a diagonal angle.
But the conversation got him thinking, and he started doing some
calculations on just how much diagonal wind the structure could
withstand. He was particularly interested in the effects of an engineering
change made during construction which had seemed caring at the time:
numerous joints were secured with bolts rather than welds. Normally such
a change was acceptable, but the Citicorp Center's design was unusually
sensitive to diagonal winds, which t...
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- Spring '14
- Structural Engineering, Skyscraper, Citigroup Center, citicorp center, William J. LeMessurier