ctbuh.org/papers Title: The Vienna Donau City Tower – 2000mm Flat Slabs as Outrigger Structure for Unique Landmark Building Authors: Klaus Bollinger, Managing Director, Bollinger + Grohmann Manfred Grohmann, Director, Bollinger + Grohmann Alexander Berger, Project Manager, Bollinger + Grohmann Subjects: Architectural/Design Building Case Study Structural Engineering Keywords: Mixed-Use Outriggers Slenderness Structure Tuned Mass Damper Publication Date: 2015 Original Publication: Global Interchanges: Resurgence of the Skyscraper City Paper Type: 1. Book chapter/Part chapter 2. Journal paper 3. Conference proceeding 4. Unpublished conference paper 5. Magazine article 6. Unpublished © Council on Tall Buildings and Urban Habitat / Klaus Bollinger; Manfred Grohmann; Alexander Berger The Vienna Donau City Tower – 2000mm Flat Slabs as Outrigger Structure for Unique Landmark Building Abstract Klaus Bollinger Managing Director The Donau City Tower I, with an architectural height of 220m, has become Austria’s tallest Bollinger + Grohmann, skyscraper, and is the new landmark building in Vienna’s skyline. The slenderness of the tower Frankfurt, Germany is extraordinary. Combined with a folded façade, Dominique Perrault Architecture created a unique shape. The occupation of the DCT 1 is divided into three parts: In the lower third of the tower there is a hotel area, in the middle is an office area, and in the top third of the tower are the Prof. Dr.-Ing. Klaus Bollinger has studied Civil Engineering residential floors. A reinforced concrete structure was used for the DCT 1. Flat slabs span between at the Darmstadt Technical University and taught at Dortmund University, Germany. Since 1994, he has been the core and the columns. Lateral stiffness to resist wind and seismic loads was achieved by two assigned Professor for Structural Engineering at the School of elements: a strong concrete core with walls of up to 1m thickness and outrigger slabs of 2m Architecture/University of Applied Arts at Vienna and since thickness above the MEP plant floor levels which activate the columns. For load takedown into 2000, a guest Professor at the Städelschule, Frankfurt. In 1983 Klaus Bollinger and Manfred Grohmann set up the office the ground slurry walls, arranged in squares, were applied below the foundation slab. Strong Bollinger + Grohmann, now located in Frankfurt, Vienna, Paris, comfort criteria were required by the client, thus a tuned mass damper was applied in order to Oslo, Melbourne, Berlin and Munich. They delivered their reduce wind accelerations. Thanks to the close cooperation of all parties, the building could services, among others, for the New ECB-Premises, Frankfurt (185m), the DC Tower, Vienna (220m), the Blade, Seoul be successfully completed and was among the finalists of the CTBUH Award: Best Tall Building (292.5m), and SkyWalk Residence, Seoul (333m). Europe 2014. Manfred Grohmann Keywords: Mixed-use, Outriggers, Slenderness, Structure, Tuned Mass Damper Director Bollinger + Grohmann, Frankfurt, Germany The Donau City Tower I, with 220m architectural height Austria’s tallest skyscraper, is the Prof. Grohmann has studied and taught Civil Engineering at new landmark building in Vienna’s skyline northeast of the river Danube. The project the Darmstadt Technical University. Since 1996 he has been assigned Professor for Structural Design at Kassel University, was challenging considering the structural aspect ratio. The slenderness of the tower is since 2000 guest professor at the Städelschule, Frankfurt and extraordinary, with a relation of structural width to height of nearly one to ten. Combined since 2007 at the ESA – Ecole d’Architecture, Paris. In 1983 Klaus Bollinger and Manfred Grohmann set up the office Bollinger with a folded façade Dominique Perrault Architecture (DPA) created a very unique shape. + Grohmann, now located in Frankfurt, Vienna, Paris, Oslo, Melbourne, Berlin and Munich. They delivered their services for The Tower 1 is the first part of a building complex that has been developed from the idea of the New ECB-Premises, Frankfurt (185m), the DC Tower, Vienna (220m), The Blade, Soul (292.5m), (170m), SkyWalk Residence, “two pieces of a gigantic monolith that seem to have split into two unequal halves, which Seoul (333m) and the Opernturm, Frankfurt (170m). then open to create an arch with undulating and shimmering façades that bring the newly created public space to life in the void created there” (DPA). The construction of the second Alexander Berger Project Manager tower DCT 2 is currently postponed. Bollinger + Grohmann, Frankfurt, Germany The occupation of the DCT 1 is divided into three parts: In the lower third of the tower there is hotel, in the middle part office use, and in the top third of the tower there are residential floors. Alexander Berger joined Bollinger + Grohmann Ingenieure in 1996. In his current position as a project manager he is The structural design of the DC Tower was done by a corporation of the engineers of Bollinger responsible for the structural design of a variety of national Grohmann Schneider (BGS), with Gmeiner and international projects of different scales throughout all design stages. Mr. Berger has a profound knowledge in the Haferl (GH), both located in Vienna. Due to lateral analysis of buildings, especially high-rise buildings, wind the complex structural challenges, it was engineering and seismic design. Among many other projects he has been in the team of the New ECB-Premises, Frankfurt agreed to perform all calculations separately (185m), DC Tower, Vienna (220m), The Blade , Soul (292.5m), in both offices by independent analysis and (170m), SkyWalk Residence, Seoul (333m), KT Headquarter, Seoul (110m), Opera Tower, Frankfurt (170m). different software (BGS: Etabs, GH: SCIA). Thus it was possible to check the structural systems and the analysis results thoroughly and independently from each other. The design of the DCT 1 follows the Austrian Code B4700, which complies with Eurocode 2 for concrete reinforced structures [5]. The structural challenges, which mainly result from the slenderness of the building, were to provide a structural system which was feasible to resist gravity loads, wind and seismic loads as well as to limit deformations and accelerations due to wind loads. Figure 1. View from the Southwest River Side (Source: Michael Nagl DPA Adagp) 540 | CTBUH 2015 New York Conference Figure 2. Design of DCT 1 and 2 (Source: DPA) Vertical Load other assumption was that the slabs stiffness will be around 30% of the non-cracked For vertical load takedown, flat slabs span section in ultimate limit state. This system was between the core walls and the columns applied for the design of the slab, slab to core in the façade transfer the loads into the and slab to column connection, regarding foundation. bending moments, shear capacity, and axial Figure 3. Section of DCT 1 (Source: DPA) forces on the columns. It was also considered Slabs for serviceability limit state design. takedown from the first view. But it had to be The reinforced concrete slabs are supported considered that there would be a different Cantilever at the Folded Façade by the core and the columns. The typical time dependent vertical deformation of span is ~6.5m on two sides of the façade The folded façade is one of the most iconic the composite columns compared to the and ~8.50m rectangular to the narrow sides architectural elements of the Donau City concrete core walls. These effects mainly of the façade. The thickness of the typical Tower. The south east façade is split into result from creep and shrinkage of the slab is 250mm, which is quite slender for ten undulating vertical ribbons which have concrete elements and they were described the maximum span of 8.5m, but it has been different inclinations. As a result its distance for structural systems of different materials in shown to be appropriate when the bending- to the column axis is changing from floor to [1] and [4]. The basis of the analysis of these resistant supports of columns and the core floor and from row to row. The cantilever of time-and load-dependent processes on the walls were considered. Double head studs the floor slabs is different in every floor (see DC Tower was the German Concrete Design had to be applied in some areas in order to Figure 7). To enable a cantilever of up to 6.2m Code DIN 1045-1 [6], [7], which complies with raise the shear capacity. All wide spanning the slabs are supported on small inclined the current Eurocode 2 regarding this. The slabs have a precamber of 20mm. Column columns. The angle and the position of these effect of creep and shrinkage was applied shortening had to be considered by support additional columns ensure that the resulting accordingly for the construction stage of each deformations as well as additional shear loads cantilever is never more than two meters. The story and for the columns and the core walls. from wind for the design of the slabs. inclined columns had to fulfill fire resistance The construction stage loads were applied as requirements as well as the requirements of The design of the slabs as flat slabs without temperature loads for the structural analysis the architects regarding the surface. Thus any beams or thicker parts enables a very in the etabs stability model. The effects of prefabricated concrete columns were applied efficient and flexible architectural design. MEP creep and shrinkage in the core walls were for these columns. ducts for heating and cooling are integrated significant. Due to core wall shortening, parts in the slabs. The floor to floor height is ~3.5m, Columns of the loads in the core walls were planted via the clear height is 3m. The minimization of the outrigger structure on the columns, which the story heights allows a number of 60 floors In the variation studies on the lateral system meant that there would be a considerable within the limited height of the building.