The new home for professional services firm Deloitte and the Bank of New Zealand is being developed and built by Brookfield Multiplex, an integrated and diversified property business with activities in construction, property development, property funds and asset management, services and infrastructure. The high profile site, on the corner of Queen Street and Shortland Street, is intended to be seen as the cornerstone for any future development of Auckland’s central business district.
“The comparatively lighter composite floor solution achieved by using ComFlor® 80 provided a number of advantages in seismic, gravity and foundation design.”
The podium-plus-tower building not only marks the position of the harbour’s shoreline in pre-European times, but also provides a treasured link to the past by incorporating the main elements of the façade of the 1940s Jean Batten Building. It’s being constructed on the CBD’s only ‘island site’, meaning that it will front onto Queen Street, Shortland Street, Fort Street and Jean Batten Place, offering a unique contrast to the abutted buildings standing shoulder to shoulder down ‘The Golden Mile’. The new Deloitte Centre will be Auckland’s most advanced environmentally sustainable major building, utilising a range of architectural and engineering techniques in order to be awarded 5 Green Stars under the New Zealand Green Building Council’s Office Rating Design Tool. Two principal considerations have been addressed to achieve this: Brookfield Multiplex’s desire as developer to position the building at the forefront of environmental technology, and the Bank of New Zealand’s requirement as a key tenant that the working environment of the bank’s headquarters be visible in Auckland’s main commercial conduit – Queen Street.
The Australian firm of architects, Woods Bagot, was invited to compete with three other firms to secure the right to design the building. Woods Bagot invited New Zealand architects Warren and Mahoney to collaborate with them and won the competition in January 2004. The final iteration of the building design was one of many that were put forward; it went through an extensive review process by Brookfield Multiplex, BNZ, the Auckland City Council and its Urban Design Panel.
“ Because of ComFlor 80’s deep profile, typically spans of 4.2m are unpropped for a 150mm thick floor. The result is faster erection and a shortening of the construction programme.”
Three sides of the Jean Batten building have been retained together with a portion of the upper floors – a band approximately 4.5m wide. These determined the floor to floor heights in this part of the building. A temporary structural steel gantry was designed to support the façade and the upper floors during the removal of part of the Jean Batten Building. The gantry also provided support during the basement excavation and the construction of the new building and was demounted in September 2008 for future recycling.
Holmes Consulting Group was appointed as structural engineers for the project; Tony Galavazi of Holmes says that because the site is located on reclaimed land, a secant piled wall was chosen as the preferred option to be constructed around the perimeter of the basement to retain the soil pressures and keep the water table at bay. “Before the site could be excavated, the main support columns had to be in position; they are fabricated from 50mm thick plate, 600 x 600mm, weigh 670kg/m and are founded in reinforced concrete bored piles. The secondary columns are founded on reinforced concrete pad foundations, and the central concrete core is founded on a reinforced concrete raft.
“During the excavation of the four basement levels,” says Tony, “a top-down construction sequence was
followed to support the 265 interlocking concrete secant piles. This involved constructing a section of the concrete slab around the site perimeter to act as a ring beam, bracing the secant wall at ground level and again at B2 basement level. The B4 basement level has been designed to be fully tanked (watertight) to resist the imposed hydrostatic uplift pressures.
The basement car park drove the 8.4m grid,” adds Tony, “and initially a precast Double Tee flooring system was investigated. But the comparatively lighter composite floor solution achieved by using ComFlor 80 provided a number of advantages in seismic, gravity and foundation design. We were able to reduce the weight of the flooring by more than 30%. Because of ComFlor 80’s deep profile, typically spans of 4.2m are unpropped for a 150mm thick floor. The result is faster erection and a shortening of the construction programme.
D&H Steel Construction Ltd fabricated and erected the steel frame. Managing Director Mike Sullivan says the Deloitte Centre is a good example of collaborative modern steel construction. “The tower columns had to be set with absolute accuracy. To accommodate building services, the steel beams were increased to a 650mm flange depth and web penetrations were used to reticulate the services within the ceiling void. The beams have been specifically designed for design actions at the locations of the penetrations, some of which are reinforced in our workshop before being brought to site.
For the podium (the first seven floors), the steel columns were delivered to the site four levels in height. We achieved a steady, cyclical construction turning over at a rate of one floor a week (1,800m²) providing continuity for the follow-on trades. Now that we are starting on the tower (13 levels each approximately 1,400m²), that rate will quicken. A second crane has been added in order to match the construction tempo.”
The adaptability of steel is one of its great construction strengths, as shown at the entrance to the basement.
As has been mentioned, the grid of 8.4m was determined by the basement parking requirement. But to accommodate two passing vehicles, the entrance had to be widened beyond the 8.4m grid to 11m. The solution was for D&H Steel to fabricate a massive transfer beam 1600mm deep and weighing 800kg/m.
One of the key features of the building is the double-skin façade at the western (Queen Street) side, which is being fitted to both the podium and tower components. It’s comprised of two, separate glass façade elements separated by a 600mm ventilated air cavity that allows warm air heated by solar radiation striking the outer skin to rise. Thus the inner glass skin remains cool. Known as the stack effect, the systems draws cooler air into the cavity through inlets at the base of the external skin to replace the buoyant warmer air extracted at the top. At each floor level, walkways allow access for maintenance and window cleaning. The double skin system is lightly constructed to maintain a high level of transparency.
Other features of Environmentally Sustainable Design:
- Installation of high energy, variable speed drive chillers, pumps and fans that reduce electrical demand during non-peak periods.
- Installation of smart building control systems, including outside air ‘economy’ cycles and after hours cycles to increase fresh air in the building and reduce energy consumption.
- The lighting layouts and zoning are engineered to minimise energy consumption and optimise lighting uniformity.
- Use of energy efficient “T8” light fittings combined with daylight sensors and dimming of perimeter zone light fittings when adequate natural light is available, and use of motion sensors to activate lighting in areas of intermittent use including lobbies, meeting rooms and bathrooms.
- A comprehensive energy metering system is to be installed to enable detailed measurement and monitoring of actual energy consumption. This tool will enable the building manager and tenants to monitor the actual operation of the building.
- Water consumption reduced using WELS rated sanitary fixtures and fittings that use low volumes of water.
- Rainwater harvesting for flushing water to the toilets.
- Use of zero ozone depletion materials for refrigerant gases and insulation materials.
The façade of the Jean Batten Building and that of the new building maintain their own integrity yet share the site harmoniously. However, the contrast between the old and the new has been softened.
A canopy cantilevers some 15m over the Queen Street corner. Rising 10m above the top of the building, the
‘Sky Catcher’ roof feature is a structural steel truss that takes a 20m stride across the Queen Street face. “Looking up at this face,” says Richard Voss of the Warren and Mahoney team, “pedestrians will see a whole series of cassettes or carefully proportioned ‘boxes’. The Deloitte Centre comprises 23,000m² of Net Lettable Area over 19 levels, as well as four levels of basement, with completion scheduled for late 2009. Deloitte and the Bank of New Zealand have signed long-term leases to fully occupy the office tower.” (Main article text sourced from SCNZ magazine, Nov 2008).
To learn more about ComFlor, the Deloitte Centre project, or other projects that have used ComFlor to their advantage call +64 9 271 1780 to arrange an in-practice presentation from one of our representatives.