The Sky Tower is an observation and telecommunications tower located on the corner of Victoria and Federal Streets in the Auckland CBD, Auckland City, New Zealand. It is tall, as measured from ground level to the top of the mast, making it the tallest free-standing structure in the Southern Hemisphere, and the 12th tallest member of the World Federation of Great Towers. Due to its shape and height, especially when compared to the next tallest buildings, it has become an iconic Auckland structure, often used in logos and promotions.
The upper portion of the tower contains two restaurant levels (one, 'Orbit' with revolving seating, turning 360 degrees once every hour ) and one cafe level, as well as two observation decks (including some with sections of glass floor). The tower attracts, on average, 1,450 visitors per day (over 500,000 per year).
The tower also features the SkyJump, a 192-metre 'fan descender' jump (an experience between a bungy jump and a base jump) from the observation deck, during which a jumper can reach up to . The jump is guide-cable-controlled to prevent jumpers from colliding with the tower in case of gusts. Climbs into the antennae portion (heights) are also possible for tour groups.
As well as for entertainment, the tower is used for telecommunications and broadcasting with the Auckland Peering Exchange (APE) being located on Level 48. Several radio broadcasting companies co-locate transmitters and share antenna systems, while television company Canwest (who ran the TV3 and C4 channels) has secondary transmitters on the tower, their primary one being at Waiatarua.
Pictures of the colour-coding can be seen at the SkyCity website here
As during the winter months, electricity consumption in New Zealand increases dramatically, and with much of the power reserve in the country depending on the water level of the hydro-lakes, various power-saving schemes are introduced to prevent blackouts. In an effort to promote power saving, SkyCity turned off the tower lighting in Winter 2008, retaining only the flashing red aviation lights. SkyCity is also minimising façade flood lighting across its complex. Simon Jamieson, General Manager SKYCITY Auckland Hotels Group, said: "Like every New Zealander, we are concerned about the country's electricity supply, and we believe it is our responsibility to make this move to assist with the power saving request." The tower was reilluminated on August 4 in time for the 2008 Summer Olympics.
Fletcher Construction was the contracted builder for the project while engineering firm Beca Group provided the design management and coordination, structural, geotechnical, civil, mechanical, electrical, plumbing, lighting and fire engineering services. It was designed by Gordon Moller of Craig Craig Moller, and has received a New Zealand Institute of Architects National Award as well as regional awards.
Taking two and a half years of construction time, the tower was opened on March 3, 1997, six months ahead of schedule.
The tower is constructed of reinforced, high-performance concrete. Its diameter shaft (containing three lifts and an emergency stairwell) is supported on eight 'legs' based on 16 foundation piles drilled over deep into the local sandstone. The main shaft was built using climbing formwork.
The upper levels were constructed from composite materials, structural steel, precast concrete and reinforced concrete, and the observation decks clad in aluminium with blue/green reflective glass. A structural steel framework supports the upper mast structure. During construction of concrete, of reinforcing steel and of structural steel were used. The mast alone weighs over . It had to be lifted into place using a crane attached to the structure, as it would have been too heavy for a helicopter to lift. To then remove the crane, another crane had to be constructed attached to the upper part of the Sky Tower structure, which dismantled the big crane, and was in turn dismantled into pieces small enough to fit into the elevator.
The tower is designed to withstand wind in excess of and resist earthquakes with a 1,000 year return period. Analysis shows that an earthquake centered away and reaching 7.0 on the Richter magnitude scale is expected to leave the tower practically undamaged. Even an earthquake measured at a magnitude of 8.0 (10 times stronger than a 7.0 quake), and located only away, is not expected to collapse the tower. As an additional safeguard against emergencies, fireproof rooms on the lower levels of the observation deck would provide refuge in the unlikely event of a conflagration, while the stairwell itself is also fire-safety rated.
The sky tower has so far been closed at least once for weather-related reasons, during a storm in November 2006, when the structure started to sway noticeably in winds of up to . The closure was noted as not having been strictly necessary except for visitor comfort, as the tower has been designed to sway up to one metre (39 in) in high winds of up to , which are expected to occur only once in 1,000 years on average.