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object:Sydney Opera House (extension) type:opera house
location:Sydney state:Australia
architect:Jørn Utzon, Kopenhagen materials:precast concrete
published:BFT 11/2006 page:4 - 6

Extension to Sydney Opera House

Symphony of precast parts

Without doubt, the Sydney Opera House is one of the most important and well-known buildings in the whole world. However, what is not so well-known is that this fabulous building was erected of precast concrete elements. Now the first exterior change to the building has been completed since its opening in 1973.
Always mentioned in the same breath as the Eiffel Tower in Paris, Big Ben or The Statue of Liberty, this building can a landmark in Australia. However, one aspect - at once obvious to a more expert visitor - is not always so well recognised. The most intensively-used concert hall in the world is not only a cathedral of music, the building is also an artwork of precast elements.
This becomes clear when the famous and extremely characteristic roof construction is viewed from below, lined with white-glazed ceramics, compared at times with a shell, at times with a sailing ship. From inside the building, the precast element beams, reminiscent of ribs, all spring from one junction point, arranged radially like a paper lantern.
The geometry of the roof surfaces which are placed on these, curved and pushed into one another, faced the engineers of the time with a totally insoluble problem regarding the execution of the design. The solution was finally found by the architect himself in 1961, who named it a "spherical solution": He used the same spherical surface geometry for all the shell sections, "so that the roof ribs can follow meridianal curves on spheres with the same radius". All these elements were produced on site as precast elements.
The entire area of the podium, with its wall areas, the upper plateau and the associated boardwalk along the water is clad or covered with large-scale precast parts. The edges of all these elements are rounded off in the same way (with a bevelled edge) and lend the podium area a uniform visual effect down to the fine detail. The striking reddish colour originates from the addition of a type of granite which is typical for the region, won from a quarry in the state in which the Sydney is located.
Since the beginning of the new millennium, comprehensive modification and renovation works have been carried out, which have gently brought the building up to the changed standards. This also included the first intervention as regards the visible structure since the building was completed 33 years ago. The monolithic, closed podium section was opened up towards the harbour on the west side with a glass frontage at the height of the boardwalk.
With the renovation of the glass facade, nine openings were also created which are shielded on the outside by an almost 45 m long Colonnade. Three of the new openings serve as doors, while the remaining six are closed with low-set fixed glass panes. The window profiles were mounted to the external face of the precast reveals, providing on uninterrupted view of the harbour from within the foyer.
In order to fit the extension into the existing form of the building as harmoniously as possible, the original concrete formula with the same addition of reddish granite was used for manufacturing the precast cladding of the new Colonnade, and also for the new facade elements of the podium which were needed. In the same way, particular attention was paid to the formation of the characteristic rounded edges during production. The new components, which all originate from the precast element factory of Hanson Precast, are up to 1,200 mm x 6,600 mm in size.
In order to make the surfaces of the free-standing supports as smooth and free of pores as possible, and in order to achieve perfect corners with perfectly sharp edges, these were manufactured of self-compacting concrete. Following various test runs, the manufacturing company decided to cast the columns, measuring 400 mm x 400 mm x 3,000 mm, in their standing position. In this process, the concrete was pumped into the steel mould from below, the first time that this manufacturing method had been used in Australia.
The official opening ceremony for the finished project was presided over by Queen Elizabeth II and took place in March of this year. Now the next phase of refurbishment of the western foyers is to follow, comprising conversion of the interior rooms according to the current designs of the architect. Utzon justified his recent involvement by referring to his concern for people and the generations which are to follow us: he was only ever interested in the human face of architecture. And it was precisely for this that he received the most celebrated architecture prize in the world in 2003 - the Pritzker Prize.
Robert Mehl, Aachen