Roy Billington Associates has worked alongside Shedkm and King McAllister a number of times, and we know what is expected of us as structural engineers. Shedkm always sees the structure as an implicit part of the architecture rather than a hanger for some architectural clothing.
This means the structure is 'detailed to death'and almost each bolt and weld has to be negotiated. We welcome this approach because we know the building design will embrace the structure and look great. As a practice, we believe structural engineering is about 10 per cent structural design and 90 per cent building construction; this realisation allows us to think laterally and design imaginative yet buildable structural solutions.
For the Ashfield Healthcare building, the site showed reasonably solid rock strata quite close to the surface, allowing mercifully unchallenging foundations, given the complexity of the superstructure.
The ground-level car park structure is based on three lines of columns at 15.9m centres across the building and 9m along.Each arm of these Vshaped columns carries a line of beams 3m apart, giving a 6m x 3m rhythm of floor beams, each consisting of a fabricated plate girder with cellular holes in the web. To achieve the long spans, the beams were designed to be composite with the precast concrete slab, which itself is composite with an in situ topping.
The upper-storey structure is based on a regular 6m grid of four rows of columns, and as a result of this layout none of the upper storey columns coincide with those of the lower storey. The first-floor columns are carried by deep transfer beams, which are expressed on the elevations.
The roof is also of composite construction, consisting of two semi-rigid frames connected by bracing across the central boulevard slot.
The composite beams and slabs were used as diaphragms to manage the wind loads by transferring these to the in-situ concrete walls of the auditorium drum and other concrete elements.
One of the pay-offs of the careful detailing of the structure was that there were very few problems in constructing some very intricate connections and members on site. Another was that our sense of adventure was maintained for the full length of the project and not just for the honeymoon period.