Shell House is constructed immediately adjacent to a number of substantial buildings. Due to its proximity to the Melbourne Underground Rail Loop tunnels, a vertical prestress was applied to the ground to enable excavation to proceed without heaving of the tunnels due to release of overburden pressure. A single wall site-retention system using site precast soldiers and sprayed infill walls to a depth of some 17 metres was used to avoid the need for underpinning adjacent properties and provide a finished face wall of minimum cost and thickness.

The 2,200 sqm floors of the office tower are curvilinear in form around a curved core structure and are totally column free. Thin slabs span between partially prestressed ribs (800mm x 450mm) which span 14.7 metres between core and perimeter columns. The depth of ribs reduces to 400mm at the perimeter and 350mm at the core, so that services can run within the structural depth. The partially stressed ribs enhance deflection performance of the floor over the large spans and enabled early stripping of formwork.

The façade of the building is polished reconstructed granite precast concrete, backformed to the floors to avoid scaffolding and provide early “closure” of the building for following trades. The columns are also precast and show as external ribs in the façade. Concrete core walls were jumpformed and included polished precast panels backformed to all external surfaces. The technology to incorporate this feature in the jumpform was developed by the Bonacci Group.

Attention to buildability aspects and fast construction systems enabled a five-day cycle to be achieved for the tower floors.

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