SRINIVASA H. IYENGAR (1934-2019)

BY JOSEPH COLACO, WILLIAM F. BAKER, AND MARK SARKISIAN

SRINIVASA H. “HAL” IYENGAR, a structural engineering partner at Skidmore, Owings & Merrill (SOM) who developed new ways to create tall buildings and long-span structures, died on July 4, 2019, at age 85.

In a career spanning four decades with SOM, Hal engineered some of Chicago’s — and the world’s — most visible and complex buildings. He worked closely with Fazlur Khan, also a National Academy of Engineering member (elected 1973) and SOM partner, to create the tubular structural systems for 875 North Michigan Avenue (formerly the John Hancock Center) and Willis Tower (formerly Sears Tower), which was the tallest building in the world from 1974 until 1998. Later in his career, he collaborated with architect Frank Gehry on the Guggenheim Museum Bilbao.

Hal was born in French Rocks, India, to Ananthachar and Rathnama Iyengar in 1934. His father was a civil engineer who designed bridges and dams in Karnataka. Early in his life, Hal planned to follow in his father’s footsteps, earning a bachelor’s degree in civil engineering from the University of Mysore in 1955 and a master’s degree in hydraulic and civil engineering from the Indian Institute of Science in 1957.

Hal was interested in more than bridges and dams; he was captivated by building design, particularly skyscrapers, and by American culture. As a child, he would sneak out of his house and head to the local cinema, where movies such as Singing in the Rain, Portrait of Jennie, and The Best Years of Our Lives offered a glimpse of the United States. He dreamed of creating the types of large-scale buildings that were prevalent in American cities, and at age 23 moved to the United States to attend the University of Illinois Urbana-Champaign, where he received a second master’s degree, in civil and structural engineering, in 1959 — as well as his nickname “Hal.” The following year, he joined SOM, which offered exactly what he sought: the opportunity to design skyscrapers and long-span structures.

Hal had a knack for explaining the complexities of structural engineering, and the collaborative model at SOM was the perfect setting for that skill. He rose quickly at SOM, becoming an associate in 1966, associate partner in 1969, and structural engineering partner in 1975. When Khan passed away in 1982, Hal became the firm’s lead structural engineering partner, a post he held until 1992. Through each of these years, he left his stamp on the architecture of SOM through his technical expertise and his conviction that powerful and heroic building structures can, under the right circumstances, be the basis of a purer design aesthetic by being themselves the focus of the architecture.

Two of his most visible projects, the former John Hancock Center and the Sears Tower, are the focal points of Chicago’s skyline and embrace his philosophy. The Hancock Center, designed in the 1960s with Khan and SOM architectural design partner Bruce Graham, fostered a new era in skyscraper design. It was the world’s first mixed-use tower, and Khan worked with Hal to develop the first exterior diagonalized tube structural system specifically for its construction. Its columns, diagonals, and tie members create a clear architectural expression for which the 100-story building remains known, and the precedent it set for high-rise design earned a Twenty-five Year Award from the American Institute of Architects in 1999.

Following the work on the Hancock Center, the same design team took its ideas even higher in Chicago’s Loop, for the 1,450-foot-tall Sears Tower. Pioneering the use of “bundled tube” construction, the basic structure consists of nine 75-foot-by-75-foot, column-free square tubes at the base, forming a cellular-tube frame. The nine bundled structural tubes, each rigid within itself without internal supports, rest on reinforced concrete caissons that descend to bedrock. The tubes are bundled together as a closed square up to the first 50 stories, and then terminate at varying heights to create the tower’s distinctive, multi-tiered form. Its lightweight building skin, a black aluminum and bronze-tinted glare-reducing glass, defines the exterior, creating one of the city’s most identifiable landmarks.

In addition to the Chicago towers, Hal’s signature projects include the McMath-Pierce Solar Telescope enclosure on Arizona’s Kitt Peak, the composite steel-concrete system for the First Canadian Centre office complex in Calgary, the cable-stayed steel roof of the McCormick Place Convention Center expansion in Chicago, and the exposed steel exoskeletal Hotel Arts Tower in Barcelona. He engineered multiple structures in London’s Broadgate development, including Exchange House, a building-bridge hybrid that spans 78 meters over a functioning railway station. In 2015, Exchange House — like the Hancock Center — also won the AIA Twenty-five Year Award.

Upon retiring from the partnership, Hal remained with SOM as a consultant. It was during this time, starting in 1992, that he began working on the Guggenheim Museum Bilbao with Gehry. The architect, who designed a swirling, geometrically free-form building for the Spanish city, originally envisioned using concrete for the structure. But Hal, who had a deep knowledge of building materials, convinced Gehry to create a structure that would be simple and lightweight, and worked with his team at SOM to design a discretized structural steel fabric grid to support the varying shape of the building. The segmented steel lattice frame was prefabricated and enabled completion of the project on time and on budget. Two years after its completion, in 1999, his structural engineering work received the Innovation in Civil Engineering Award from the American Society of Civil Engineers (ASCE).

For many of his projects, Hal wrote or co-authored case studies and research papers explaining the technical details of his innovations and how his concepts could be adapted to other buildings. He and Khan were the first to propose a wide range of structural systems for tall buildings composed of both structural steel and reinforced concrete. Hal pioneered the practical application of fire engineering research on exposed structural steel for Exchange House and the Hotel Arts Tower. In the 1980s, he developed a system for high-rise buildings, in which a large reinforced concrete core with structural steel outrigger trusses connected to steel perimeter columns — a concept uniquely suited to towers with multiple setbacks or irregular forms. This idea heavily influenced the design of future skyscrapers, such as SOM’s 88-story Jin Mao Tower in Shanghai.

Hal earned numerous accolades and leadership positions in the building industry. He was a fellow of ASCE and the Institution of Structural Engineers in London. He served on the Advisory Board at the University of Illinois Urbana-Champaign’s College of Engineering, chaired the Building Seismic Safety Council’s Structural Design Committee, and won lifetime achievement awards from ASCE, the American Institute of Steel Construction, the Council on Tall Buildings and Urban Habitat, and the Structural Engineering Association of Illinois. In 2000, he was inducted into the National Academy of Engineering.

But beyond his contributions to the practice of structural engineering, he touched the lives of all the people he worked with. He oversaw the expansion of structural engineering in all of SOM’s offices — in Chicago, Denver, Houston, and other cities — and fostered a culture of collaboration and hard work among his staff. He learned valuable lessons in creating some of the world’s most recognizable landmarks and passed that knowledge onto future generations of engineers.

“He always professed that when you have a problem, the best thing you can do is immediately face that problem head on,” said longtime SOM colleague and friend John Zils. “Never let it sit and fester. He’d face an issue squarely and solve it. That was a good lesson that I always remembered from Hal, and it was great advice not only in engineering, but in life as well.”

Upon retirement, Hal and his wife of 52 years, Ruth Yonan Iyengar, spent the winter months in Sanibel Island, Florida, and later moved to Fort Myers. Together with Ruth and his son and daughter, Jay and Sona, Hal traveled to see landmark buildings around the country and the world. In many of these trips, and in Florida, he spent hours in parks and nature preserves, birdwatching and observing other wildlife. In Florida, he also took up journaling, and throughout his life he was an avid bridge player and was known for a powerful serve on the tennis court.

Hal is survived by Ruth, Jay, and Sona; his sisters Kumuda Doreswamy and Prabha Bhashyam; two grandchildren; and numerous nieces, nephews, and other relatives.