From a certain angle, Melbourne’s Marina Tower looks like a conventional building, straight and tall. Turn a corner and you can’t believe your eyes. Is the structure falling over? Australia’s fastest growing city now has its own iconic calling card, an off-balance, eye-catching housing complex which dominates the city’s Docklands area. The complex is comprised of three buildings, a seven storey Sheraton hotel and two co-joined residential towers, one 43 storeys tall and the other 36. Collectively called Marina Tower, the co-joined towers rise in unison until they split off from each other at a five degree angle at the 21st. floor. The distance between the two towers increases the higher the elevation.
The conventional way to build skyscrapers is to build a central core, an exterior frame and stack floor plates on top of each other. But why be conventional? The project’s architects, DKO Architecture, say deviating from the norm allows more sunlight to enter the upper apartments and gives the residents an unobstructed view of the harbour and downtown. The leaning effect has been exaggerated by lighter and darker floor-to-ceiling windows. Not surprisingly, the complex has been dubbed the leaning towers of Melbourne. Move over Pisa.
Marina Tower joins a handful of contemporary leaning towers including La Puerta de Europa, a Madrid office complex built in 1996 and 1997’s Marine Traffic Control Tower in Lisbon. Unlike those earlier structures however, Marina Tower’s continual lean doesn’t start at the base but halfway up and that creates special problems. “You’ve got an inclined load coming down which then goes vertical,” says Paul Webber of Webber Design the structural engineers on the job. “Because of the higher load [the diaphragm slab] is around 450 to 500 mm thick which has got a lot more reinforcing in it to take those horizontal compression loads.” That’s 19 inches of reinforced concrete. A normal concrete floor is 8 inches thick. The slab is tied back to the core or central elevator shaft. The upper floors are also supported by thick columns that separate into a vertical column and an inclined column. “Transitioning columns diagonally is common. We’ve done that on a lot of projects,” says Webber.
Marina Tower was an engineering challenge but Webber says its outcome was never in doubt. “We have high strength concrete and we have high strength steel. The technology and the design software to do his was never a question.”
In fact, Marina Tower opened months ahead of schedule, contributing 461 apartments to the housing market. Once derided as an urban wasteland because of its lack of amenities, Docklands is enjoying new popularity as grocery stores, pharmacies, restaurants and bars flood into the area. So too are the city’s newcomers and as a consequence, Docklands and its leaning tower has become a go-to area.
