By Tara Hoke
While this column all too frequently focuses on unethical behavior, it is important to recognize that most ASCE members and engineers uphold high standards of professional conduct even in challenging situations. In light of the recent passing of William J. LeMessurier, P.E., Hon.M.ASCE, the 1993 recipient of ASCE's George Winter Award, this article commemorates his praiseworthy and exemplary behavior upon discovering a serious flaw in the design for New York City's Citicorp Center.
Situation
The 59-story Citicorp Center, one of New York City's most distinctive skyscrapers, was the brainchild of the structural engineer William J. LeMessurier and the architect Hugh Stubbins, Jr. A deal struck by Citicorp and St. Peter's Lutheran Church, the original landowners, allowed Citicorp to build a structure on the site if it also constructed a church on the northwest corner of the block that would not be connected to the skyscraper in any way. To accommodate this requirement, LeMessurier devised an innovative structure in which the skyscraper rested atop a central core and four immense 114 ft (34.8 m) columns set at the midpoint of each side of the building. This design made it possible for the structure's corner to be cantilevered over the new church on the northwest, and it created an open plaza on the southwest corner.
LeMessurier's design also included a unique wind brace system comprising 48 braces arranged in a six-tiered V pattern on each side of the building. The system was intended to enhance the structure's lateral stability by channeling stress from the building's corners to the steel support columns at the center of each facade.
In June 1978, one year after construction of the skyscraper was completed, LeMessurier received a call from an engineering student in New Jersey requesting more information about the design. According to the student's professor, LeMessurier had placed the columns incorrectly. In revisiting his calculations, LeMessurier became aware of a serious flaw in the building's design.
At the time, New York City's building code required testing of a building's resistance only to perpendicular winds. Yet the placement of the support columns at the midpoint of each facade, rather than at the corners, meant that a greater risk to the structure's stability was presented by diagonal winds. When LeMessurier tested his wind brace system against winds hitting a column at an angle of 45 degrees, he realized that the winds increased the tension in four of the eight affected girders by 40 percent, substantially more than he had anticipated.
The increase in tension on the wind brace system would not have been a significant concern to LeMessurier if he had not recently learned of an on-site modification to his original design. His design had specified that the diagonal girders be welded to the support columns at the center of each facade; however, since welded joints were both expensive and commonly regarded as needlessly strong, LeMessurier's New York office had approved a change to bolted joints. Even more troubling was the news that while American Institute of Steel Construction specifications required an extra safety margin in the strength of joints in structural columns, the people on LeMessurier's team had chosen to regard the diagonal braces as trusses, not columns; thus, the number of bolts securing the joints had not provided for this extra margin of strength.
As a result of these design flaws, LeMessurier estimated that the Citicorp Center would be able to withstand only a 16-year storm, not the 50-year storm the building had supposedly been designed for. The design had also included a tuned mass damper, which might have lessened the risk of failure, but the damper relied on electric power and thus would provide no protection in the event of a power outage. With hurricane season on the horizon, LeMessurier believed that the potential for strong diagonal winds presented a significant risk to the newly occupied skyscraper.
Question
In light of his discovery of a serious flaw in the Citicorp Center design, what were LeMessurier's obligations under the ASCE Code of Ethics?
Decision
Canon 1 of the code reads as follows: "Engineers shall hold paramount the safety, health, and welfare of the public . . . in the performance of their professional duties." Paragraph (a) in the guidelines to practice for this canon elaborates: "Engineers shall recognize that the lives, safety, health, and welfare of the general public are dependent upon engineering judgments, decisions, and practices incorporated into structures, machines, products, processes, and devices." Moreover, canon 6 has this to say: "Engineers shall act in such a manner as to uphold and enhance the honor, integrity, and dignity of the engineering profession." As further guidance, paragraph (a) in the guidelines to practice for canon 6 states that engineers shall "not knowingly engage in business or professional practices of a fraudulent, dishonest, or unethical nature." Although these excerpts are from the current edition of the code, the canons cited have remained substantially unchanged since 1976.
Given the evident risk to public safety, LeMessurier had an ethical obligation to take steps to remove the threat. After verifying his calculations with an outside consultant, LeMessurier notified the building owners of the design flaw and the serious risk that the building posed to public safety. He proposed a plan to reinforce the wind braces by welding steel plates 2 in. (51 mm) thick over each of the bolted joints; meanwhile, he recommended that electric generators be installed to power the mass damper system and that stress gauges be placed throughout the structure to allow constant monitoring of the building's condition.
Working virtually around the clock, LeMessurier's team made the necessary repairs to the wind brace system before the arrival of the fall storm season; the reinforced skyscraper is now estimated to be capable of withstanding a 700-year storm. LeMessurier's reputation was not damaged by the design mistake; rather, he was widely lauded for his professional integrity. Most important of all, his response upon discovering the problem served to protect occupants and visitors to the Citicorp Center from a possible building failure.
Tara Hoke is ASCE’s general counsel and a contributing editor to Civil Engineering.
© ASCE, ASCE News, July, 2007
