For many Australians, the Sydney Opera House is known as an architectural triumph — a tribute to the ingenuity of the Danish visionary Jørn Utzon, whose flights of imagination bestowed upon Sydney Harbour a global icon.
The Opera House is as much a feat of engineering as it is a work of architecture, and a plaque unveiled last week atop the building’s podium steps acknowledges not just the work of Utzon, but also lead engineer Ove Arup and Peter Hall, the architect who took over after Utzon resigned from the project in 1966.
“The impact I can see in this building, and on the buildings that were built in the 50 years since it was finished, is profound — not just here in Australia, but all around the world,” said Arup Deputy Chair Tristram Carfrae at an Opera House symposium exploring the site’s conception, innovation and renewal.
“It was a time of can-do mentality. Post-war, everyone embraced the future as a good thing. They welcomed it; they tried to move forward as fast as they can.”
Carfrae said he did not think Arup had worked on a project that saw more innovation at once than the Opera House — and although the building was opened 50 years ago this past October, those innovations are still helping to push new projects forward.
Concert hall to cathedral
Barcelona’s famed Sagrida Familia cathedral, for instance, an unfinished church that might yet take decades to complete, is being constructed with techniques that Arup pioneered in Sydney.
“We’re using exactly the same technique of casting concrete on to tiles — or proposing to at least — in the cross on top of Gaudi’s Sagrada Familia,” Carfrae said.
“We’ve made the main towers now at Sagrada by modern methods of construction, prefabricating — in this case, stone — pieces, post-tensioned together using steel tendons, and lifted into place.”
The technique involved placing tiles upside down at the bottom of the formwork, then casting a skin of concrete just 45 mm thick on the back, which was reinforced with ribs. The tiles were then lifted and put into place using brackets.
“These are extraordinary pieces of engineering design, these brackets. I’ve looked at [them] for a long time trying to work out how somebody created something that worked so well,” Carfrae said.
“Made out of bronze, so they’re corrosion resistant [and] what they allowed was to take up the tolerance — the difference — between the structure, which is built to roughly plus or minus 25 mm, to create a surface which is flush with absolutely uniform panel gaps.
“They continue then in service to take up the different movement and temperature; the tile needs to grow and shrink every day as the sun comes out, and the structure behind doesn’t. They’re extraordinary bits of engineering — more than one million tiles were placed in moulds.”
The construction of the building was a pioneering use of this glued-segmented construction technique.
“At the back of the casting beds was where the precast elements were cast; in the front of that was the storage yards. And then they’re trucked to either the front or the back of the Opera House and lifted up by these three track-mounted cranes — these enormous cranes that were imported especially for the project,” Carfrae said.
“It’s rather ironic that the Royal Institute of British Architects now refers to this method as ‘modern methods of construction’ — a phrase that they coined in the last 10 years — but was actually in practice here 60 years ago.”
Each of the Opera House’s ribs were match-cast against its neighbour, because only 3 mm of epoxy resin glue was used as filler in the joint.
“How courageous is that?” Carfrae marvelled.
Even today, he said, not many buildings make use of this technique.
“But it is now the typical way of building bridges,” Carfrae said.
“In Singapore, the Jubilee bridge, designed with [architect] Phillip Cox, was built using this technique. You have precast elements being glued and stressed together to make the bridge itself.
“Or on a bigger scale, a bridge in Corpus Christi in Texas is currently under construction — it will be the largest cable stay bridge in America when it’s finished.”
The unusual geometry of the building also required techniques new to the engineers of the day. The building’s shells, for instance, required advanced mathematics to be brought into being.
“As a structure, they’re very complex; they don’t know whether they’re working in bending or in membrane forces,” Carfrae said.
“That’s why they’re not a shell, but a rigid arch membrane-shell hybrid, and they were eventually resolved by the use of digital computers.”
These computers — Ferranti’s Pegasus and Sirius models — were giant valve-tube machines operated in London and Southampton, UK.
“The young engineers had to write their own computer programs to make this work,” Carfrae said.
“It stretched the capacity of the machinery at the time. In fact, the shells had to be done in two analyses that were then blended together.”
One of the engineers involved in those computations, Peter Thompson, told create that it was like “working with the stone age” compared to contemporary computing power.
“I remember [engineer] Peter Ross and I used to go down on a Friday night and feed in all the data we’d written during the day and sit there all night while it churned away,” he said.
“If you designed one arch by hand it took about two weeks, but it took about 20 minutes on the computer. That’s the difference.”
A show for the ages
Despite the many decades of artistry that have been on display at the Opera House over its 50 years of operation, Carfrae believes it debuted before a single aria had been sung in its halls.
“I would hold that actually this assembly — which went on in the full view, of course, of everybody in Sydney — was really the first performance of the Sydney Opera House,” he said.
“It was its own construction, with the cranes in the background gradually retreating towards the sea until they had nothing left to do.”
And that is an advance repeated today — again at the Sagrada Familia.
“What’s happening as Sagrada is that the whole cost of the construction is paid for by the people who come and watch it being constructed. You can build anything anywhere, if you can pull off that trick,” Carfrae said.
“You are changing construction into a work of theatre: literally a performance. It’s no longer a detriment or an annoyance, a nuisance [in] its local community, but something that people want to come and watch being done.
“And it all started [with] this project.”