Stage One of construction of the Sydney Opera House rendered at the time the largest concrete structure in the Southern Hemisphere.
Two major problems confronted the engineers in their approach to Stage One. First, the geology of Bennelong Point had not been surveyed accurately at the time of the competition guidelines, which assumed that the promontory comprised Hawkesbury sandstone mass, like the surrounding land; whereas in fact, it was made of loose alluvial deposits permeated with seawater and completely unsuitable for bearing the weight of the intended structure.
Some 700 steel-cased concrete shafts, nearly 1 metre each in diameter, were bored down into the perimeter and northern half of the site. Mass concrete foundations filled in the unstable rock in the central area of the site. Given all this preparatory work, it is not hard to understand why building contractor Civil and Civic's quote for the work was so inaccurate.
Utzon's submission sketches suggested that the Concourse area under the Monumental Steps would require some form of colonnade to support the weight of the structure above. When Arup saw this detail, he dismissed the need for the columns, describing instead the undulating shape of the now famous Concourse beams.
The beams, in their final design, so successfully dispersed moments of stress that no additional vertical support was necessary. They provide a beautiful and dramatic sweeping form to the underside of the Monumental Steps, which continue up through the levels of entrance finishing just under the beginning of the vaulted arches.
From March 1958 on, the awe-inspiring form of the Podium rose out of the enormous building site on Bennelong Point, slowly transforming the promontory. It was at the time the largest concrete structure in the southern hemisphere.
Australian author Patrick White described the construction site as evoking the ruins of Mycenae, in Ancient Greece.
Stage One would take five years to complete, closing on the original estimate of time for the Opera House project as a whole. Even then it would require substantial modification to withstand the final designs for the roof.
Yet Sydneysiders began to comprehend the incredible feat of design and engineering underway in the name of culture.
Created by Sam Doust and the
Sydney Opera House GCI Team
State Library of New South Wales