Opera House chief engineer, Sir Jack Zunz, dies aged 94 (1923-2018)

When it comes to the Sydney Opera House roof structure, the very symbol of Sydney, we have lost our number three man, and the man who made certain its completion. Sir Jack Zunz, who led Ove Arup’s engineering team to realise Jørn Utzon’s wonder, died on December 11 in London, aged 94.

Within a week of his move from South Africa to Ove Arup’s London office in August 1961, Zunz, then only 37, was handed the central crisis of the entire Opera House project. That, after four years of development, no workable roof structure could be found.

Utzon knew what he wanted geometrically: connected shells that would each spring vertically from sharp points on the ground, clear their internal spaces, then quickly turn towards their inclines. His consulting engineers gave him parabolas in 1958 and assured him a structure could be made, but time and again the forces near the point foundations proved too large.

Sensing the urgency, and seeing the problem through fresh eyes, it was Zunz who separated the roof of each hall into three separate structures, each standing on a stable four- or six-point footing. It vastly simplified the structural analysis. Look closely at the two most northern shells of each hall and you will see Zunz’s innovation, hidden within a visual trick.

It was no coincidence that Utzon chose his spherical solution a mere month after Zunz’s arrival. Zunz had assembled the necessary components for the right conversation with Utzon. He had hedged his bets wisely: with the separation of structures now accommodating the forces, Utzon could either have his original smooth concrete shells, or he could have a series of prefabricated concrete ribs, an idea that had slowly evolved in the Arups office.

Utzon unequivocally preferred the ribs, and within days he proposed that the ribs of every shell could also be prefabricated with the same geometry, since each shell had roughly the same curvature. The series of parabolas became a single sphere and progress was unlocked.

The criticality of Zunz’s role was obvious to everyone by 1962. With Utzon, he travelled to Sydney to present the new design to the NSW Government and to promote it to the nation on live television.

Later that year, when Melbourne’s King Street Bridge collapsed and Premier Heffron panicked at the thought of his own pending construction, Public Works Minister Ryan first phoned Zunz and asked that he and Utzon come to Sydney once more.

That fear of collapse would occupy Ryan’s thoughts for the rest of his ministership. The roof report commissioned by Ryan in 1964 bore Zunz’s name, giving assurances to the government that the roof was possible. He was trusted by his client throughout, on both sides of politics.

Indeed, of all the key actors in the history of the Opera House project, Zunz’s network of trust was perhaps wider than any other. He was a master collaborator. Zunz was fired by Utzon’s vision as much as anyone, but never blind to the contributions of others.

Ultimately, at the moment of truth for the Opera House, that balance allowed Zunz to integrate the people and ideas that were so desperately needed. Sydney is forever a beneficiary of his leadership.


Dr Andrew Botros is the Director of Expressive Engineering and Chair of The Warren Centre’s Innovation Advisory.


This story is featured in the 21 December 2018 edition of The Warren Centre’s Prototype newsletter. Sign up for the Prototype here.

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