Structural Influencer: Nabih Youssef

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Nabih Youssef, a leading California-based structural engineer and seismic design expert and pioneering advocate of steel plate shear walls in areas of high seismic risk, passed away on July 12, 2024, at the age of 80. Born in Egypt, Youssef, SE, F ASCE, FAIA, received a bachelor’s degree in structural engineering from Cairo University in 1967. After emigrating to the United States, he received a master’s degree from California State University, Los Angeles, in 1974 and then a postgraduate diploma in earthquake engineering from UCLA.

As the founder, chair, and CEO of his eponymous firm Nabih Youssef & Associates (NYA), he was a revered expert in the development of earthquake engineering codes and standards. Today NYA is an internationally recognized structural engineering firm with offices in Los Angeles, San Francisco, San Diego, Irvine, South Carolina, and beyond. Youssef’s visionary leadership, innovative engineering, and profound kindness left an enduring mark on the design and construction community. Youssef was a co-author of foundational documents for Performance Based Seismic Design (PBSD), which is a fundamental part of contemporary earthquake engineering.

NYA became known for undertaking landmark projects that had immediate and lasting effects on our communities. His accomplishments were many but those most important are:

Youssef delighted in historic landmarks and breathing new life into buildings. He saw value in preservation to help neighborhoods thrive, show respect for their past, and bring vibrancy to communities. A few of his passion projects included the restorations and expansions of the Ace Hotel, the Harold Examiner building, the Los Angeles Memorial Coliseum, Dodgers Stadium, and Transbay Terminal in San Francisco. He helped retrofit and restore the Getty Villa, worked on the Walter E Washington Convention Center in DC, and innovated a glass canopy structure to enclose a new atrium supported by the new addition wing of the Cleveland Museum of Art.

A registered civil and structural engineer, Youssef was one of the world’s leaders in earthquake engineering and seismic design and the development of associated standards. His position as the Chair of the Vision 2000 Committee and the Seismology Committee for the Structural Engineers Association of California heavily contributed to the enactment of PBSD, a major conceptual breakthrough for the engineering community. Youssef also chaired the City of Los Angeles’ Mayor’s Blue Ribbon Seismic Hazard Reduction Committee. He authored many technical papers, and taught classes at multiple universities, including lectures on engineering concepts and analysis for high-rise buildings. He served on the University of California Seismic Advisory Board, was part of the Building Seismic Safety Council “NEHRP” Special Programs of the National Institute of Building Sciences in Washington DC and was an Associate Editor for the publication “The Structural Design of Tall & Special Buildings” published by Wiley. He was a pioneer in the use of base isolation to protect structures seismically. His dedication to his work and collaboration with peers were leading aspects of his character.

The catastrophic failure of the Olive View Hospital and Sanitarium during the momentous Sylmar temblor of February 9, 1971, was one of the most important early influences on Youssef’s career. A graduate student in structural engineering at California State University in Los Angeles at the time, he had never felt an earthquake. “It was my first awareness of the severity of Mother Nature,” Youssef recalled to Downtown LA News in 2004. The structural failure of the hospital led to two of the 14 fatalities in the Sylmar quake despite the facility’s state-of-the-art design. This underscored the fact that earthquake engineering was “an open field and earthquake codes were not fully developed. That’s what caught my creative interest and led to my decision to immerse myself in the field,” Youssef said.

While Youssef made his name working on construction projects, his most lasting contributions could ultimately come from work that took place out of public view. Youssef sought to transform the entire philosophy underlying traditional earthquake codes. As chair of the Seismic Safety Committee of California’s Buildings Standards Commission, and as a member of many other panels, Youssef investigated the performance of buildings constructed to code standards before the 1994 Northridge earthquake. The investigation showed that steel-framed structures built to the most demanding specifications at the time were not immune to catastrophic failure during a big event. That finding added momentum to an ongoing shift away from force-based code prescriptions that lay out a list of generalized strength features that every building must have. Youssef and others urged regulatory agencies to adopt PBSD standards, which set goals ranging from preventing collapse to protecting property at various seismic intensity levels and performance objectives.

California’s State Historical Building Code is an example of standards that incorporate performance-based guidelines. “While not compromising life safety, it still allows alternative, creative methods of interventions which limit the intrusion and help protect the historic fabric of old buildings,” Youssef said. This transformation in thinking about earthquake safety deserves a good deal of credit for the downtown Los Angeles renaissance, especially along the Historic Core. People widely regarded Youssef as one of the leading thinkers among structural engineers within the adaptive reuse movement.

When it came to historic structures, such as steel frame/brick infill buildings, Youssef wanted to take advantage of the quality of the original designs. “The common view … was that masonry walls had no value. Retrofitting them required tons of shear walls and foundations, which was not feasible,” Youssef said. In fact, the intrusive intervention required under older codes sometimes did more harm than good, he added, not only to the historic character of old buildings but to their structural integrity. A better way to retrofit historic buildings, Youssef said, is to supplement the inherent strength of masonry walls with reinforced concrete frames, carbon fiber mats and other unobtrusive, lightweight materials. Those are also the most cost-effective methods.

Youssef played a key role in the booming reuse of beautiful historic buildings in the downtown, historic core of Los Angeles. Redevelopment was possible because of an improved partnership between developers and city officials who were receptive to novel approaches to earthquake design. “I wouldn’t use ‘flexible’ to describe their approach. Building officials feel guilty about that word,” Youssef said. “But I would say we now have much better collaboration between the city and leading engineering firms and practitioners. That has allowed us to implement cost-effective, elegant solutions, and in a timely manner too.”

Youssef was a husband and father of three. He created a national educational charity for children in need, https://www.copticedu.org/ and co-founded several schools. He changed the lives of countless people with opportunity, and more often with kindness.

With generosity and creativity, Nabih Youssef transformed structural engineering forever, leaving the profession better than he found it. His spirit of innovation and compassion will continue as his firm’s guiding principle as they carry his legacy forward into their next chapter. ■