"The DC Towers (also known as Donau City Towers) will be a pair of towers in Vienna's Donaucity. DC Tower 1 is complete and the first tenants moved into the offices in October 2013. Construction of DC Tower 2 will start afterwards. French architect Dominique Perrault has designed both towers.
DC Tower 1 is 220 metres high (250 metres including the antenna spire) which makes it the tallest skyscraper in Austria as it will be 18 metres higher than Millennium Tower, which was leading that ranking before. The DC Tower 1 was officially finished with an opening ceremony on Feb 26, 2014 by Buzz Aldrin. DC Tower 2 is expected to be 168 metres high which will make it Vienna's fourth tallest building.
Due to the global financial crisis 2007, ground breaking had to be delayed several times. Eventually construction was started on 17 June 2010. After slightly more than three years, DC Tower 1 is outwardly complete, while works inside the building are on-going. Work will start on DC Tower 2 after DC Tower 1 has been fully completed. Most of the available floor space will be used for offices. Baxter International has been confirmed as one of the largest tenants at DC Towers. The upper floors will be used for sky lofts, while the first 15 floors will house a four-star hotel operated by the Spanish Sol Meliá Group. There will also be a restaurant in one of the top floors. As of June 2012 tenants have been confirmed for 50 percent of the floor space according to the owner WED (Wiener Entwicklungsgesellschaft für den Donauraum)."
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"Forming and appearance
The form arose from the idea of ??a monolith split in the middle. This "jagged stone" is recognizable by the wave-like shifted structure on the south-east side, but only with tower 2 its negative form is preserved and thus spatially visually. The two towers will then form a "city gate", with the two halves of the Danube facing and slightly angled. The place that will develop in between is decisive for Perrault. Identity and urban space can only be created with several towers. The DC Tower 1 is just a good solitaire. Dominique Perrault wanted to build a uniform volume of glass and no supporting structure with four curtain facades. The black color and the reflections of the surroundings help the tower take its texture and weaken the two-dimensional image. The projectiles, which can be read from the outside, are to be placed in the background. The "liquid façade" is modeled on the Danube, as the proximity to the water is essential for the architect. It represents a great potential for the Danube City, but is currently not utilized properly. The associated element of the differently displaced "waves" is therefore to be found not only on the external skin; On the contrary, it occurs recurrently in the interior, as in the hotel rooms, for example.
The glass façade consists of 32,000 m² sun protection insulating glass and was produced in Austria. Of this, 10,000 m² of glass surfaces were screen printed; Also to reduce the risk of bird strike.
The flowing and immaterial character that the exterior reproduces has been interpreted in the interior in the opposite sense. Here the rooms should be very present and physically noticeable. In the generally accessible halls and corridors, the full-surface natural stone surfaces underline the robust aesthetics. The lift lobbies were again designed with metal panels, which radiate a material-like heat through their differently treated surfaces. The public hotel areas in the pedestal building are connected by a "floating" spiral staircase, the staircase at the same time forming an atrium that tapers upwards, which opens the view of the tower. Their round steps are covered with white Bianco Sivec marble from Macedonia and are tapered on the sides. "
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"Construction
In addition to a detailed investigation of the subsurface, the main reason for the design of the load-bearing structure was the wind susceptibility; Both on the tower as well as outgoing from him. As a result, a model of the tower and its surrounding area was built in order to examine it in the wind tunnel. With regard to the fall winds occurring in the Danube City, the wind comfort should also be optimized in the ground-near zone. The results of the investigations were easy adaptations to the building structure and the positioning of screen-like constructions around the tower. These also protect against sunlight and falling objects.
The reinforced concrete construction is elastic. At the top of the 58th floor, the tower can vary up to 45 centimeters. In order to reduce the movement below the perception limit and to increase user comfort, a vibration absorber in the form of a 305-ton mass pendulum was installed between the 56th and 60th floor. It consists of steel plates and a 54 m³ water tank, which in case of emergency ensures the supply of the wall hydration system. The pendulum hangs at the four corner points on two 16 m long steel ropes. It is rail-guided, thus oscillating in defined paths and is tuned to the slender building side. The pendulum always moves in the opposite direction to the natural oscillation of the tower. The line length can be adjusted variably to the final natural frequency. However, this did not occur until some time after completion, since a newly built structure is initially relatively stiff and only becomes more elastic over time.
The so-called outriggers, which give the DC Tower more stability, are installed in the building technology floors on levels 16/17 and 43/44. Two-meter-thick steel concrete ceilings connect the core to the supporting outer supports and improve the stiffness of the support system. The outrigger days are twice as high as a regular floor, reserved for domestic installations and can only be seen from the outside at the ventilation openings, which are latticed in the façade. However, the outrigger construction as such is not readable. The projecting bay windows of the south-east side of the shaft are supported or supported by steel profiles which are subjected to tensile or compressive stress. "
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