Architecture buffs had the opportunity to hear two of the craft’s most renowned practitioners speak at Yale this week.

French architect Paul Andreu and former School of Architecture dean Cesar Pelli expounded on their work, the challenges of designing great buildings in the 21st century and architectural theory. Andreu delivered the 24th Paul Rudolph Lecture sponsored by the School of Architecture on Monday and Pelli spoke as part of the Chubb Fellowship on Wednesday.

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During his talk, Andreu used his own work as a “point of departure” for larger discussions of architectural theory.

Monday’s discussion was characterized by Andreu’s obvious emotional attachment to his work. The famed architect of airports such as Charles de Gaulle in Paris — and whose recent work, the new Opera House in Beijing, is making an international splash in the architectural world — explained that the end of a project provides an opportunity for reflection on architectural ideas.

“When you finish a big work you get the baby blues,” he said. “And the only way to cure it is to go back to some origin and the principles that have guided you and to accept the time as a moment to consider theory.”

In all of the airport terminals he has designed, Andreu said, he has paid particular attention to openness, passage and the use of light. But some questioned Andreu’s open designs when Charles de Gaulle’s Terminal 2E collapsed in 2004, killing four people.

Andreu presented pictures of the terminal Monday night for the first time since the incident, and insisted his design was not the cause of the tragedy.

“It was a problem of construction, not design,” he said.

Although Andreu said he does not want to die as an “airport architect,” it was clear that his work with transportation has influenced his designs elsewhere. In Beijing, for instance, just as at Charles de Gaulle, Andreu focused on the way in which people move through — and process into — his Opera House.

“You have to bring people into a theater,” he said. “How should you enter an opera? The passage, as in airports, is essential.”

Pelli, who served as dean from 1977 to 1984, worked early in his career with Eero Saarinen ARC ’34 on iconic projects like Morse and Ezra Stiles Colleges at Yale and the TWA terminal at John F. Kennedy International Airport that Andreu called his “inspiration” for his work with airports.

After working with Saarinen, Pelli moved to the West Coast and designed the famed Pacific Design Center in West Hollywood, Calif., also known as the “Blue Whale.” In yesterday afternoon’s lecture, Pelli discussed how he and his firm dealt with the challenge of adding to the Center when its owners wanted to expand.

“We had to make the new buildings look like they belonged,” he said.

Like Andreu, Pelli noted his open designs, specifically his design for the Cooperative Arts & Humanities High School in New Haven, which features large glass windows making features such as the dance studio visible from the street.

“I drive by every day during construction on the way to my office, but I can’t wait until it opens,” he said. “I hope it will be a place where students want to go, not like the typical high school.”

Pelli’s firm has completed three major projects on Yale’s campus: the Thomas Golden Jr. Center, the Malone Engineering Center and the renovation of the Yale University Press. He is currently designing a new home for the Molecular, Cellular and Developmental Biology Department, which is slated for completion in 2011.