CHICAGO—Eli W. Cohen, a structural engineering pioneer who helped forge the Chicago skyline and founded the consulting firm that became the Thornton Tomasetti Chicago office, died May 2, at his home in Evanston, IL. He was 80 years old, and had been a leading member of the Chicago engineering community since the mid-1950s.

Cohen is known for his refinement of the composite steel highrise with a reinforced concrete core, and for nearly a half century collaborated with world-renowned architects on many Chicago landmark buildings. His firm, Cohen-Barreto-Marchertas (CBM), served as structural engineer for more than 350 projects and more than 70 high-rise buildings.

Cohen worked closely with leading developers—such as the John Buck Co., U.S. Equities, The Prime Group, Mesirow Stein, Hines, and LR Development—and with world-renowned designers, including Helmut Jahn, Philip Johnson, Tadao Ando, Cesar Pelli, and Ricardo Bofill.

"Eli will be best remembered professionally for his many Chicago highrise buildings, and personally for his generosity and humanity," said Daniel Marquardt, managing partner of the Thornton Tomasetti Chicago office who worked in Cohen’s firm for 20 years.

"Eli led by example," said Bob DeScenza, Thornton Tomasetti executive vice president, who succeeded Mr. Cohen in 1993 in managing the Chicago office. "We will miss his leadership and ability to mentor staff. Eli truly enjoyed contributing to the profession as a structural engineer. His collaborations with the world’s greatest architects had a profound impact on Chicago’s skyline."

"Eli represented the heart and soul of structural engineering," said Richard Tomasetti, Thornton Tomasetti chairman. "His accomplishments and spirit will always be with us."

Born in Germany in 1927, he and his family fled the Nazis and moved to Palestine in 1935. After high school, he served as a communications officer in the Haganah, fighting for Israeli Independence in 1948. He boasted his low army number on his license plate, and it was his good luck number throughout his life.

Cohen moved to the United States in 1953 and received his civil engineering degree in 1955 from the University of Illinois. During the summers, he worked as a singing waiter in the Catskills to put himself through school. He briefly worked on bridges for the Illinois Division of Highways. He joined Paul Rogers Associates, a structural engineering firm in Chicago, became a partner in 1965, then president and principal of CBM in 1969. In 1993, CBM merged with Thornton Tomasetti.

Under his leadership, CBM pioneered the use of a composite steel structural system. This involved the integration of a reinforced concrete core wall, to resist lateral loads, with a light steel floor framing. The development of 50- to 60-story buildings became more feasible and efficient because the lighter framing reduced construction time and expense, and allowed for large, column-free spans, giving architects greater freedom in exterior expression.

In the early 1960s his adaptation of concrete cooling tower design to the design of highrise offices required a change in the way the unions worked. Until that time ironworkers contracts forbid members of other trades to work at higher elevations at jobsites. But the proposed system was reviewed with them and they agreed to let concrete workers work above them.

Cohen’s composite steel designs received awards from the Structural Engineers Association of Illinois for Most Innovative Design in 1987 for 10 South LaSalle Street; Best Structure Award in 1991 for 181 West Madison Street; and Best Structure Award in 1992 for 77 West Wacker Drive.

Other distinguished Chicago buildings CBM contributed to include the Xerox Center, the American Medical Association headquarters, the Swissotel, a 42-story office building at 190 South LaSalle Street, and the 50-story Leo Burnett Building.

Mr. Cohen also spearheaded numerous philanthropic efforts, particularly his firm’s involvement with the Chicago Architecture Foundation’s Newhouse Architectural Program, which gives high school students the opportunity to enter the field of architecture and design. He served on the board of Congregation Beth Emet in Evanston and led a tour in Israel that included, among other sites, a building named in his honor at the Shaare Zedek Medical Center in Jerusalem.

"Eli was ahead of his time in how he ran his firm and his life," said Clyde Baker, senior principal engineer of STS Consultants, a geotechnical engineering group. "When you walked into his office, it was like the United Nations. It didn’t matter to him where someone came from. He hired a lot of immigrants and gave them a chance."

Mr. Cohen served as president of the Structural Engineers Association of Illinois and was a member of the Chicago Committee on High-Rise Buildings. He was a registered structural engineer or professional engineer in more than 30 states. He was also active in engineering education, serving as an adjunct professor at the University of Illinois at Chicago, and as a guest lecturer at several regional colleges and for the American Institute of Architects. He served on Mayor Daley’s Advisory Commission on Building Code Amendments.

He is survived by his wife of 50 years, Georgia, three children—Larry Cohen (Sharon), Lisa Nicolson (John), and Diana Cohen (Wes Slaymaker)—and six grandchildren.

Services were held May 8, at Congregation Beth Emet, Evanston, followed by internment at Memorial Park.

The Chicago ACE Mentor Program will be awarding a college scholarship in honor of Eli Cohen. "Eli’s entire life, from both a professional and personal standpoint embodies our mission to mentor, inspire and support youth in the design and construction industry," wrote Pat O’Connell, executive director of the ACE Mentor Program of Chicago. "We are honored and grateful for the opportunity to participate in this celebration of his legacy."

In addition, the first scholarship given by the Thornton Tomasetti Foundation will be made in Eli Cohen’s name, said Dan Cuoco, Thornton Tomasetti president.

Donations may be made to the ACE Mentor Program of Illinois, Eli W. Cohen Scholarship Fund, Ms. Kathleen Fanning, c/o DeStefano + Partners, 445 East Illinois St., Suite 250, Chicago IL 60611, or Ms. Pat O’Connell at 847.328.7818 and poc99@comcast.net.