Models: The Red and Yellow Books

Models describing the early parabolic roof shape and the later move to spherical geometry.

By Sydney Opera House

Early parabolic scheme, east elevation (1958/1961) by State Records of New South WalesSydney Opera House

When in 1958 the engineers at Arup and Partners requested that Utzon define the curves of the roof, he took a plastic ruler and, holding it perpendicular to a table, made it bend. Tracing the curves, he sent them to London explaining these were the shapes he wanted.

The outcome of the first exchanges between architect and engineer produced an initial sketch of the roof in which every curvature is different, a structurally unsound form with difficult bending moments near its footings.

However, this first geometrical approach to the shells was also visually beautiful in a distinctly different way to the drawings Utzon had submitted for the competition.

The ridge profiles were much higher and pointed now, and the end shell form of his competition drawings no longer cantilevered like a cliff cave over the sea.

These higher profiles also allowed far more volume for the stage towers, auditoriums and acoustics.

Red Book model, view from the Monumental Steps (1958) by State Library of New South WalesSydney Opera House

Page 13, South elevation (1958) by Jørn UtzonSydney Opera House

Utzon’s architects redrew all of the elevations of the Sydney Opera House to the new forms, and these are shown in the 1958 design documentation, known as the Red Book.

Clearly the profile of the roof had changed considerably, but it was received by the client and the public as a transformation for the better, for both logistical and aesthetic reasons.

Early parabolic scheme, southwest elevation, 1958-61 (1958/1961) by State Records of New South WalesSydney Opera House

Page 11, North elevation (1958) by Jørn UtzonSydney Opera House

Red Book model, east elevation (1958) by State Library of New South WalesSydney Opera House

Thin shell structures were the form of his original sketches and much favoured by leading architects and engineers at the time. Eero Saarinen, Felix Candela and Pier Luigi Nervi had already used concrete shell membranes in world-renowned structures.

Page 10, East elevation (1958) by Jørn UtzonSydney Opera House

Front Cover illustrating the Spherical Solution (1962) by Jørn UtzonSydney Opera House

The Yellow Book presented the "Spherical Solution" - a final design rationale for the roof of the Sydney Opera House.

The form of the shells had changed again and again, as architect and engineers struggled to find a buildable structure that captured the spirit of the design and could house the complexity of a working building.

After many failures, Utzon had a now famous epiphany that would solve what had apparently become an intractable problem.

Utzon's breakthrough was to derive each of the shells from the constant and universal form of the sphere. This one decision solved a multitude of problems. It captured the essence of the original sketch, while allowing the building blocks to be prefabricated with comparative ease.

It also raised the finished building out of a style identified with the times and gave it an ageless form.

The spherical solution underpins the roof form that we see today and is explored in more detail in "The Masterful Solution" exhibit.

Sydney Opera House: projection of the Spherical Solution (2015) by LatchkeySydney Opera House

Jørn Utzon and Jack Zunz describe the approach to the roof design of the Sydney Opera House, Australian Broadcasting Corporation, 1962, From the collection of: Sydney Opera House
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Model detailing the sections of the roof in place in the form of the sphere, State Library of New South Wales, 1962, From the collection of: Sydney Opera House
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Jørn Utzon's hands display sections comprising the final form of the roof taken from a spherical model, State Library of New South Wales, 1962, From the collection of: Sydney Opera House
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Sections of the wooden spherical model set out on a mirror surface, State Library of New South Wales, 1962, From the collection of: Sydney Opera House
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Balsa and cardboard model of the spherical scheme, State Library of New South Wales, 1962, From the collection of: Sydney Opera House
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Spherical Solution, Harbour-end view of the model, State Library of New South Wales, 1962, From the collection of: Sydney Opera House
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From the beginning of their collaboration, engineer Ove Arup gently encouraged Utzon to pursue a geometry that would allow for repetition and therefore prefabrication. As early as 1958 he had suggested that the soffits of the shells (their interior surface) be ribbed to strengthen and articulate them.

Page 10, Cross sections of Minor Hall, Jørn Utzon, 1962, From the collection of: Sydney Opera House
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Spherical Solution, Concourse-end view of the model, State Library of New South Wales, 1962, From the collection of: Sydney Opera House
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By 1961, after many failures, Ove Arup and another senior engineer at Arup, Jack Zunz, resurrected the ribbed approach from 1958, pursuing the two options of a double-skinned shell structure and the ribbed form that would dramatically express the roof’s function through the exposed concrete of the shells’ interiors.

Spherical Solution, balsa and cardboard model, west elevation, 1962 (1962) by State Library of New South WalesSydney Opera House

In these models, we can see the fusion of the ribbed approach with the spherical geometry through which Utzon famously arrived at a final approach to the roof, informed by a three-year period in which Arup engineers struggled – and ultimately failed – to find a workable solution through parabolic geometry.

Page 5, West elevation (1962) by Jørn UtzonSydney Opera House

Page 27, Development of shells (1962) by Jørn UtzonSydney Opera House

Spherical Solution, bird's-eye view of the balsa and cardboard model (1962) by State Library of New South WalesSydney Opera House

Spherical Solution, bird's-eye view (1962) by State Library of New South WalesSydney Opera House

Various angles on an early model of the parabolic scheme (1960) by State Library of New South WalesSydney Opera House

Credits: Story

Created by Sam Doust and the
Sydney Opera House GCI Team

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Contributors:
Latchkey
State Library of New South Wales
State Records NSW

Credits: All media
The story featured may in some cases have been created by an independent third party and may not always represent the views of the institutions, listed below, who have supplied the content.
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