The Tower features a striking 8m high ground floor lobby and 26 passenger lifts serving the 36 column-free office floors from a central concrete core. The perimeter columns are spaced at 9m centres, and a reduced depth edge beam enables the ceiling margin to be recessed, offering minimal interruption to the full-height glazing that surrounds the entire floor plate.
Two alternative systems were explored during design – one a substantial perimeter truss at plant levels, to serve as an alternative load-path in the event of column loss; the second a high level of blast hardening of vulnerable columns at lower levels. Given that no bollard line could be achieved to give stand-off from the tower perimeter, the design blast selected was extremely onerous, assuming large vehicle-borne and person-borne devices located immediately adjacent to the columns.
This involved ‘jump-starting’ the core by building it from a grid of plunge columns at the upper basement level, and later casting the pile cap and infilling core walls as the construction above and below ground progressed. To enable accelerated construction of the tower basement and core pile cap, the walls of the 12m deep basement were designed to be excavated with a single prop at ground floor level, while minimising the movements of the adjacent highways.
The modified construction sequence saved six months from the programme, and enabled Brookfield to go to the market for key tenants with a much improved offer, resulting in the securement of an anchor tenant early in the construction process, and a building 70% let 20 months ahead of practical completion.
Total Area: 120,000m² approx. floor area
Brookfield Office Properties
Allies & Morrison and Arney Fender Katsalidis
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