Working at the structural engineering firm until his retirement in 2009, Gianopulos collaborated with influential modern architects snd architecture firms, such as Louis I. Kahn and Venturi Scott Brown. He worked on Kahn's building for the Yale Art Gallery and the Bangladesh capitol complex in Dhaka. He also worked on Venturi Scott Brown's Vanna Venturi House and Franklin Court.

"Though his work enabled architects like Kahn and Venturi Scott Brown to transform the world of architecture, Nick remained modest and self-effacing, and he never forgot to give credit to his colleagues for their accomplishments," the firm noted in an obituary posted on its website. "He knew that working on a building is a collaborative enterprise, and he had a powerful sense of ethical responsibility as an engineer." 

After working on historic Congress Hall early in his career, Gianopulos began focusing on historic preservation work starting in the 1970s. The firm says clients such as the University of Pennsylvania's School of Design, Philadelphia Orchestra Association and National Park Service "gladly entrusted their historic buildings to Nick, and he delivered innovative yet sensitive engineering interventions that promise to serve those buildings well into the future."

Gianopulos mentored many young engineers at Keast & Hood, as well as at the University of Pennsylvania, where he taught from 1964 until 1991. He won several awards,  including the Wyck-Strickland Award, the Master Builder's Award from the Carpenter's Company and the Harley J. McKee Award from the Association for Preservation Technology. 

Gianopulos is survived by his wife, Antoinette, his two daughters, Elizabeth and Christiana, his son, Elia and two granddaughters.

A viewing at 9:30 a.m. on July 27 at St. Luke Greek Orthodox Church in Broomall, Pa. will be followed by an 11 a.m. funeral service. An internment will be held at West Laurel Hill Cemetery in Bala Cynwyd, Pa., followed by a luncheon.