Structural engineering for Australia’s tallest office tower
Creating unobstructed panoramic views for Australia’s tallest office tower and working with a unique geometry required complex problem solving and creative structural engineering solutions.
The tower’s expression by Foster + Partners responds directly to the structural stability system of direct and effective load paths and material efficiency. While a centre core is the spine of most buildings of this height, Salesforce Tower has a rear core to maximise views to the harbour.
To reduce the eccentric vertical load on the core from the long span floors and maximise floorplate efficiency by minimising wall thickness, the tower’s columns and floors are constructed from lightweight composite steel and concrete construction.
We designed a unique and highly effective stability system with an organic belt-bracing system expressed on the north facade. The bracing combines with outriggers located at the tower’s mid-level plantroom to directly activate the full width of the building, connecting the core south wall directly to the twin columns at the tower’s most northern tip. The bracing’s east and west edge aligns with the outriggers at each end of the core providing the shortest and stiffest connection across the width of the building to resist the dominant wind loading direction. In addition, the belt bracing assists in reducing the towers twist from the offset core.
Located on reclaimed land and in Circular Quay’s tidal zone, the tower’s basement is below harbour level with the heritage-listed Tank Stream, Sydney’s 19th century former fresh watercourse, under the eastern side of the building. Working with archaeological teams and the First Nations community, we designed a retention system to manage tidal groundwater.