The Vienna Donau City Tower
The Vienna Donau City Tower
The Vienna Donau City Tower
org/papers
Title:
Authors:
Subjects:
Architectural/Design
Building Case Study
Structural Engineering
Keywords:
Mixed-Use
Outriggers
Slenderness
Structure
Tuned Mass Damper
Publication Date:
2015
Original Publication:
Paper Type:
1.
2.
3.
4.
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6.
Council on Tall Buildings and Urban Habitat / Klaus Bollinger; Manfred Grohmann; Alexander Berger
Manfred Grohmann
Director
Abstract
The Donau City Tower I, with an architectural height of 220m, has become Austrias tallest
skyscraper, and is the new landmark building in Viennas skyline. The slenderness of the tower
is extraordinary. Combined with a folded faade, 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
residential floors. A reinforced concrete structure was used for the DCT 1. Flat slabs span between
the core and the columns. Lateral stiffness to resist wind and seismic loads was achieved by two
elements: a strong concrete core with walls of up to 1m thickness and outrigger slabs of 2m
thickness above the MEP plant floor levels which activate the columns. For load takedown into
the ground slurry walls, arranged in squares, were applied below the foundation slab. Strong
comfort criteria were required by the client, thus a tuned mass damper was applied in order to
reduce wind accelerations. Thanks to the close cooperation of all parties, the building could
be successfully completed and was among the finalists of the CTBUH Award: Best Tall Building
Europe 2014.
Keywords: Mixed-use, Outriggers, Slenderness, Structure, Tuned Mass Damper
Bollinger + Grohmann,
Frankfurt, Germany
Alexander Berger
Project Manager
Bollinger + Grohmann,
Frankfurt, Germany
The Donau City Tower I, with 220m architectural height Austrias tallest skyscraper, is the
new landmark building in Viennas skyline northeast of the river Danube. The project
was challenging considering the structural aspect ratio. The slenderness of the tower is
extraordinary, with a relation of structural width to height of nearly one to ten. Combined
with a folded faade Dominique Perrault Architecture (DPA) created a very unique shape.
The Tower 1 is the first part of a building complex that has been developed from the idea of
two pieces of a gigantic monolith that seem to have split into two unequal halves, which
then open to create an arch with undulating and shimmering faades that bring the newly
created public space to life in the void created there (DPA). The construction of the second
tower DCT 2 is currently postponed.
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.
The structural design of the DC Tower was done by a corporation of the engineers of Bollinger
Grohmann Schneider (BGS), with Gmeiner
Haferl (GH), both located in Vienna. Due to
the complex structural challenges, it was
agreed to perform all calculations separately
in both offices by independent analysis and
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)
Vertical Load
For vertical load takedown, flat slabs span
between the core walls and the columns
in the faade transfer the loads into the
foundation.
Slabs
The reinforced concrete slabs are supported
by the core and the columns. The typical
span is ~6.5m on two sides of the faade
and ~8.50m rectangular to the narrow sides
of the faade. The thickness of the typical
slab is 250mm, which is quite slender for
the maximum span of 8.5m, but it has been
shown to be appropriate when the bendingresistant supports of columns and the core
walls were considered. Double head studs
had to be applied in some areas in order to
raise the shear capacity. All wide spanning
slabs have a precamber of 20mm. Column
shortening had to be considered by support
deformations as well as additional shear loads
from wind for the design of the slabs.
The design of the slabs as flat slabs without
any beams or thicker parts enables a very
efficient and flexible architectural design. MEP
ducts for heating and cooling are integrated
in the slabs. The floor to floor height is ~3.5m,
the clear height is 3m. The minimization of
the story heights allows a number of 60 floors
within the limited height of the building.
Two different systems were assumed
regarding the contribution of the 250mm
slabs on the lateral system. Both systems
are limit states and consider that the real
stiffness of the slab structure is not precisely
predictable. The first system assumed that the
slabs do not contribute to the lateral system,
which was implemented by non-bendingresistant joints at the core walls and the
columns. This is the governing system for the
outrigger slab and the core wall design. The
In the end the second option was agreed: Highstrength (C70/85) RC columns and core walls
were used. The column size was increased in
the hotel floors to 1,200 x 1,200mm and in the
office floors to 700 x 1,000mm. The RC column
size in the residential floors is 600 x 600mm.
Column Axis Set-off
Figure 6. Load Transfer from the Core to the Columns (Source: Bollinger + Grohmann)
Lateral Stiffness
Maximum gust wind speed of 130 miles/hour
and seismic loads according to Mercalli scale
VII had to be considered for the DC tower.
Due to the shape and the slenderness of
the building it was important that a feasible
lateral system could be developed in the early
planning phases. Thus the main focus in the
beginning of the project was on the feasibility
studies of different lateral systems.
Feasibility Studies
Figure 7. Column Design Study (Source: Bollinger + Grohmann)
Figure 9. Truss System of the Slab Above 15th Floor (Source: Bollinger + Grohmann)
Figure 14. Idealized Truss System of Core Walls and Outrigger Slab (Source: Bollinger + Grohmann)
Figure 15. Rebar Design: Rebar Connection of Core Walls and Outrigger Slab (Source: Bollinger + Grohmann)
Seismic Loads
A response spectra analysis was performed
as the basis for the design of the seismic
elements. The ductility factor was applied to
1.5 according to the Austrian code B4015. For
the most structural elements, the wind loads
were the governing lateral loads. For some of
the spandrels which connect the core walls
the seismic load combination was governing.
Tuned Mass Damper
The 300 ton mass pendulum system was
applied in order to fulfill the serviceability
requirements regarding the maximum
acceleration in the residential floors. It is
located above the elevator shaft on top of
the building. For the design of the TMD, it
was essential to consider that real buildings
have different Eigenfrequencies compared
to the analyzed Eigenfrequency. Thus it
was necessary to provide a structure which
could react on this different behavior. The
Eigenfrequency which was measured for the
DC Tower was around 0.19Hz, which means
that more or less all the concrete elements of
the lateral system were still in an uncracked
condition,which would change under strong
wind impact. The idea which was realized was
to apply horizontal supports for the cables of
the mass, which are vertically moveable. By
this way the TMD may be adapted to different
structural behavior of the tower by changing
the structural length of the suspension cables.
Figure 16. 3D-Rebar Design: Core Walls and Connection to Outrigger Slab (Source: Bollinger + Grohmann)
Foundation
The DC tower is located directly nearby
existing buildings and an existing
Figure 17. Rebar Connection Core Walls to Outrigger Slab (Source: Bollinger + Grohmann)
Figure 18. Response Spectrum for DC Tower Seismic Design (Source: Bollinger + Grohmann)
Figure 19. Tuned Mass Damper of the DCT 1 (Source: Bollinger + Grohmann)
Construction
The construction works of the pit and the
deep foundation began in summer 2010. The
foundation works on the raft started in autumn
2010 and topping out was in October 2012,
which was primarily foreseen in May 2012.
Settlement
The settlement was predicted to ~80mm
maximum in the core area of the DCT 1 and
25mm at the edges of the foundation pit.
Last monitoring results confirmed that real
settlements were in a range of 80% (core wall
area - 90% (edge of construction pit) of the
predicted settlement.
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