108 St Georges Terrace - Design

Design

The tower was designed by architects Cameron Chisholm Nicol. The major parameter given to them in the planning of the building was that "all office areas should face the excellent views that exist of the Swan River". Working within this brief, they selected a triangular cross-section of the tower because it lent "itself to open plan office layouts" by allowing natural light to reach most parts of the working floors. Also, the stepped front of the building maximised the number of corner offices on each floor. The eastern and northern sides of the building are slip-formed concrete shear walls, and have fewer windows. These sides house the services of the building, including the lift shafts and stairwells. Some difficulty was encountered in the design stage with how to execute the diagonal slopes forming the top of these walls alongside the top five floors of the building, since a standard concrete pour was not possible. Instead, reinforced concrete panels were prefabricated elsewhere and subsequently attached to the structure.

The floor plates of the tower are constructed from conventional reinforced concrete beams and slabs. The building's 14 passenger lifts are divided into three zones: low-rise (floors G-17), mid-rise (18–29) and high-rise (30–51), thought to be the first building in Australia to use such a configuration.

The foyer of the tower was originally planned to be an open-air forecourt between the building and the remains of the Palace Hotel, however extensive aeroelastic wind testing of the structure by the Institute of Environmental Sciences at Murdoch University forced this area to be covered with a glass canopy. Mocks of the curtain walls to be used in the tower were also tested to 1.5 times the proof load to ensure they could withstand cyclone-force weather and seismic shocks. The building is clad with green-tinted double-pane glass on windows, with the service core and structure of the building covered with aluminium sheeting skin coated with a light grey fluoropolymer paint.

Upon completion, the mass of the building above ground was 66,000 tonnes (150,000,000 lb). The building rests upon 43 belled concrete and steel piles, of average length 30 metres (98 ft), which go "through 3 layers of swamp" to solid siltstone bedrock. These piles range in diameter from 2.5 metres (8 ft 2 in) to 2.9 metres (9 ft 6 in). The basement of the building has a depth of 16 metres (52 ft), and has a 0.5-metre (1 ft 8 in) thick diaphragm wall to prevent water ingress.

While the building was under construction, on 21 September 1987 the Perth City Council approved the addition of a 48-metre (157 ft) spire to the top of the tower to house television and radio antennas, microwave antennas, navigation lights and surveillance cameras. However, when asked about the surveillance cameras, the R&I Bank's development spokesman Terry Pilbeam denied any knowledge about what any cameras would be used for. The spire was also approved by the Department of Transport and Communications, which said the spire would cause no air traffic problems, and the spire was added to the building upon completion.