Today’s demand for highly transparent building envelopes calls for innovativesolutions. Cable-stayed glass façades make it possible to dematerialize the buildingenvelope so as to make it almost imperceptible. Werner Sobek has designed a greatnumber and variety of cable-stayed façades. The primary structural system carryingmost of these façades consists of straight tension members (e.g. tension rods,cables), typically in a parallel arrangement. The tension members transfer the deadload of the glazing very efficiently to the supports. Under wind load the membersundergo large deflections thus activating their lateral stiffness. As a result, thedetailing of these façades requires innovative design approaches and special care toallow for such large deflections. Besides this, each project has its individualchallenges such as a complex geometry, large openings, difficult edge conditions,warping of IG units, bomb blast requirements, etc. The present article gives anoverview of the development of cable-stayed façades as designed by Werner Sobekover the last 15 years. The overview includes completed projects as well as façadescurrently under construction or in the design phase

Blandini, L.

Feierabend, S.

Sobek, W.

Tarazi, F.

English

TU Delft Open Access Journals

Challenging Glass 2 – Conference on Architectural and Structural Applications of Glass, 
Bos, Louter, Veer (Eds.), TU Delft, May 2010. 
Copyright © with the authors. All rights reserved.  
Cable-stayed glass façades - 15 years of 
innovation at the cutting edge 
Werner Sobek, Steffen Feirabend, Lucio Blandini, Frank Tarazi 
Werner Sobek Stuttgart, Germany 
steffen.feirabend@wernersobek.com, lucio.blandini@wernersobek.com, 
frank.tarazi@wernersobek.com  
Today’s demand for highly transparent building envelopes calls for innovative 
solutions. Cable-stayed glass façades make it possible to dematerialize the building 
envelope so as to make it almost imperceptible. Werner Sobek has designed a great 
number and variety of cable-stayed façades. The primary structural system carrying 
most of these façades consists of straight tension members (e.g. tension rods, 
cables), typically in a parallel arrangement. The tension members transfer the dead 
load of the glazing very efficiently to the supports. Under wind load the members 
undergo large deflections thus activating their lateral stiffness. As a result, the 
detailing of these façades requires innovative design approaches and special care to 
allow for such large deflections. Besides this, each project has its individual 
challenges such as a complex geometry, large openings, difficult edge conditions, 
warping of IG units, bomb blast requirements, etc. The present article gives an 
overview of the development of cable-stayed façades as designed by Werner Sobek 
over the last 15 years. The overview includes completed projects as well as façades 
currently under construction or in the design phase.  
Keywords: Glass, Cable-stayed glass façades, Case studies 
1. Introduction 
The demand for dematerialized façades and highly transparent building envelopes has 
increasingly pushed architects and engineers to the limits of technical feasibility. The 
façade of the Bioclimatique Greenhouse in Paris (RFR and Adrien Fainsilber, 1986) and 
the atrium façade of the Hotel Kempinski (Murphy/Jahn and Schlaich Bergermann, 
1993) are milestones on the development of cable-stayed glass façades. The former is a 
cable truss holding a glazed façade, while the latter is a cable net façade that is 
prestressed both horizontally and vertically. Both projects were an important step 
towards transparent building envelopes. Werner Sobek and his team have pushed the 
boundaries of transparency even further. This development started in 1995 with the 
design of the 40 m high façade of the New Bangkok International Airport.  
 
The façade of the Bangkok Airport is one of the largest cable truss supported glass 
façades in the world. The reduction of the primary structure to its bare essentials led to 
the development of cable-stayed façades characterized by only straight prestressed 
tension members oriented in just one direction. Compared to conventional cable net 
structures (i.e. structures oriented in two directions) and cable trusses, this typology 
allows not only for an increased transparency, especially at the corners, but also leads to 
better solutions for openings, non-planar surfaces, support conditions, etc. 
Challenging Glass 2 
 
The tension members (e.g. tension rods, cables) transfer the dead load of the glazing 
very efficiently to the supports. Under wind load these members show large deflections 
activating their lateral stiffness. Over the years special solutions were developed to keep 
the deflections as small as possible and to obtain a homogeneous curvature in the 
deflected state to improve the warping condition of the individual glazing units. Special 
attention was paid to functional and aesthetical detailing (i.e. glass fixing) and on the 
design of sensitive fields such façade openings and corners. 
 
 
Figure 1: Principle primary structural systems of cable-stayed façades [1] 
2. Realized Projects 
2.1. Sony Center – Hotel Esplanade, Berlin 
At the Sony Center in Berlin, completed in 2000, only vertical tension rods were used 
for the primary structural system. A highly transparent glass façade was to shelter the 
protected remnants of the former Hotel Esplanade. Together with the architect Helmut 
Jahn from Chicago, Werner Sobek developed a façade that is 60 m wide and 20 m high. 
The primary structure consists of pairs of tension rods with spring supports. The glass 
panels are placed between pairs of tension rods, thus avoiding eccentric loading that 
may result out of the self-weight of the glazing. Four drilled point fixings have been 
used for each glass panel (2 m x 2 m, FT).  
 
Spring base supports keep the pretension force in the rods almost constant, 
independently of temperature changes. The Esplanade facade allows for horizontal 
deflections of up to 60 cm under wind loads. A similar design approach was used by 
Dewhurst Macfarlane and Partners for the façade of the Kimmel Center in Philadelphia, 
completed in 2001. In this case, however, the pretension force in the cables is kept 
constant by cast iron weights at the cable supports rather than by spring supports [2].  
 
Cable-stayed glass façades - 15 years of innovation at the cutting edge 
 
Figure 2: Sony Center – Hotel Esplanade, Berlin 
2.2. ZBUB, Bremen 
This facade of a new foyer building of the University of Bremen was designed by 
Werner Sobek and the architect Jan Störmer. The building was completed in 2000. The 
façade’s main structure consists of fully locked cables (∅26mm) that are set 1.8 m apart 
from each other. The cables have spring supports to keep the pretension force almost 
constant under temperature variation and snow loading on the roof. The 15 m high 
façade can deflect up to 35 cm under wind loading. The glass units (1.8 m x 0.9 m, FT) 
have four clamped point fixings in the horizontal joints. Clamped point fixings instead 
of drilled point fixings have been used to minimize the local stress concentration in the 
glass. These point fixings are connected eccentrically with the fully locked cables, thus 
inducing bending in the cables. 
 
In order to allow for a fully glazed corner Werner Sobek introduced a joint between the 
cable-stayed façade itself and the rigid façade structure in the corner. The joint is 
formed by two vertical glass fins. Brushes between the fins ensure a high level of 
insulation even when the cable-stayed facade deflects under strong wind loading. 
 
Challenging Glass 2 
        
Figure 3: ZBUB, Bremen 
2.3. Bayer Headquarter, Leverkusen 
At the Bayer headquarter in Leverkusen (architect: Murphy/Jahn, Chicago, completion: 
2002) Werner Sobek used open spiral cables with spring supports spaced at 1.5 m to 
each other [3]. Contrary to the ZBUB project, however, the glazed corner is not 
separated by joints from the rest of the façade to achieve an even more transparent glass 
corner. The deflection of the façade at the building corner area is homogenized by flat 
springs behind the horizontal joints (as shown in figure 4), thus minimizing the warping 
of the glass panels. The laminated glass panels (1.5 m x 1.8 m, FT) are held by clamped 
point fixings at the corners of the panels. The self-weight of the glass units is connected 
eccentrically to the cable. 
 
 
Figure 4: Bayer Headquarter, Leverkusen 
Cable-stayed glass façades - 15 years of innovation at the cutting edge 
2.4. O‘Hare, Chicago 
The new glass façade of Terminals 2 and 3 of the International O’Hare Airport in 
Chicago was designed by Werner Sobek together with Murphy/Jahn. This was the first 
time that insulating glass units were used for such a cable-stayed facade. The primary 
cables are open spiral cables (∅32mm and ∅20mm) spaced 3 m apart. These cables 
were strongly prestressed to minimize the overall deflections of the façade, thus also 
reducing the warping of the IG units (3.0 m x 1.4m, FT and HS). Each IG unit is 
supported by four clamped point fixings. Beside the wind loading scenarios the IG units 
were also designed to fulfil blast mitigation requirements. 
 
The IG units are suspended via secondary tension members within the vertical glass 
joints. This helps to avoid eccentric loading of the primary cable which may otherwise 
result from the heavy self-weight of the IG units. Since there are various entrances into 
the terminal building, a solution had to be found for the many joints resulting from these 
openings. Werner Sobek developed profiles similar to convoluted rubber gaiters to deal 
with particular situation thus limiting the warping of the IG units. 
 
 
Figure 5: O’Hare, Chicago 
2.5. Lufthansa Aviation Center, Frankfurt 
The Lufthansa Aviation Center in Frankfurt was completed in 2005 following a design 
by Ingenhoven Architects. The comb-shaped structure has ten 'fingers' linked by fully 
glazed atriums. In order to achieve maximum transparency, the external façades of these 
atriums are designed as a cable-stayed façade, the only load-bearing elements are 
vertically tensioned cables. The IG units (1.45 m x 3.45 m, FT) are supported by pairs 
of vertical open spiral cables (∅28 mm) spaced 1.45 m apart. Each IG unit transmits 
wind loads to the cables by means of six clamped point fixings. Two of these fixings 
also transfer the self-weight of the IG units to the cables. The arrangement of the cables 
in pairs allows the efficient transfer of the self-weight via a force couple – tension and 
compression – into the prestressed cables. 
 
Challenging Glass 2 
       
Figure 6: Lufthansa Aviation Center, Frankfurt 
 
The 25 m high facade can deflect up to 40 cm under wind loading. A smooth transition 
between the rigid façades of the fingers and the flexible cable-stayed façades of the 
atrium is ensured by glass fins with brushes, an approach already used in the above-
mentioned ZBUB project. 
2.6. European Investment Bank, Luxembourg 
The European Investment Bank in Luxembourg is another project of Werner Sobek with 
Ingenhoven Architects that uses cable-stayed glass facades. The largest façade within 
this project is 22 m high and 45 m wide. The primary structure consists of vertical 
cables (∅30 mm) that are fixed at the top to the bottom chord of a long-span underslung 
beam. 
 
      
Figure 7: European Investment Bank, Luxembourg [4] 
Cable-stayed glass façades - 15 years of innovation at the cutting edge 
The argon-filled IG units (3.54 m x 1.75 m, FT) have six clamped point fixings – two in 
the horizontal joint and four at the corners. Two of the four corner supports transfer the 
self-weight of the glass pane to secondary stainless steel cables (∅14 mm) which are 
hidden in the vertical glazing joints. 
 
The transition to the rigid parts of the building envelope is again provided by vertical 
glass fins. A double set of sliding gaskets between the moveable and the fix part of the 
glass fins ensures the required air and water tightness at the joint. 
2.7. Emil Schumacher Museum, Hagen 
The façade of the Emil Schumacher Museum in Hagen was designed by Lindemann 
Architekten together with Werner Sobek. A glass envelope encases a cube where the 
exhibition rooms proper are located. The 16 m high glass façade is supported by one-
way oriented prestressed cables (∅30 mm) spaced 3 m apart. Flexible heating tubes in 
the glass joints shall prevent condensation water. The glazing consists of argon-filled IG 
units (1 m x 2.95 m, FT) with four clamped point fixings. 
 
 
Figure 8: Emil Schumacher Museum, Hagen 
3. Projects under Construction 
3.1. Doha Convention Center, Qatar 
The Doha convention centre and tower will bring a breathtaking aspect to the Doha 
skyline. Werner Sobek and his team designed together with Murphy/Jahn the facades of 
the convention centre using two different types of cable-stayed facades. The southern 
and western façade have only parallel horizontal prestressed cables. The IG units are 
hung with tension rods in the vertical joints to the roof girder. The eastern façade has 
vertical prestressed cables. The detailing of the facades required special attention as the 
facades are also inclined and curved [5]. 
Challenging Glass 2 
3.2. Ferrari & Maserati Museum, Italy 
The Ferrari & Maserati Museum in Modena was designed by Future Systems. Werner 
Sobek modified and improved the cable-stayed façade design and is in charge of 
engineering the whole façade of the museum up to construction.  
Such a complex double curved façade, whose height varies from 6 to 11 m, has been 
solved by using only a set of vertical stainless steel cables (∅32 mm), located 
eccentrically. Special attention was paid to controlling the deflections of the whole 
façade as well as the warping of the most critical IG units (max. size 2.0 m x 1.25 m) by 
fine-tuning every single cable pretension force.  
 
 
Figure 9: Ferrari & Maserati Museum, Modena 
 
 
Figure 10: Ferrari & Maserati Museum, Modena - inside 
 
Cable-stayed glass façades - 15 years of innovation at the cutting edge 
4. Summary 
Since 1995 Werner Sobek has continuously worked towards an ever-increasing 
transparency of the building envelope. The reduction of the façade primary structure to 
its bare essentials led to cable-stayed façades with only one-way oriented parallel 
prestressed tension members. Such cable-stayed glass façades allow to dematerialize the 
façade to an almost imperceptible glass envelope. 
5. References 
[1] Sobek, Werner; Kutterer, Mathias; Feirabend, Steffen; Sundermann, Wolfgang: Konstruieren mit Glas – 
Festigkeit und Tragverhalten. in: Glasbau Atlas. 2. Auflage, Institut für internationale Architektur-
Dokumentation GmbH, München, 2006, pp. 90-118. 
[2] Macfarlane, Timothy: The Development of Single Direction Cable Support Glass Walls. in: GPD 
conference proceedings 2003, pp. 265-267. 
[3] Sobek, Werner; Rehle, Norbert: Beispiele für verglaste Vertikalseilfassaden. in: Stahlbau 4/2004, pp. 
224-229. 
[4] Sobek, Werner; Tarazi, Frank: Ein weiterer Schritt hin zur entmaterialisierten Gebäudehülle - das neue 
Verwaltungsgebäude der Europäischen Investitionsbank in Luxemburg. in: Bauingenieur 1/2010, pp. 29-
35 
[5] Beer, Benjamin: Glazed cable façades and special structures – Focus on complex geometries and 
warping deflections of insulating glass units. in: GPD conference proceedings 2009, pp. 419-424. 
 
Challenging Glass 2 
 


Cable-stayed glass façades - 15 years of innovation at the cutting edge

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Cable-stayed glass façades - 15 years of innovation at the cutting edge

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