FLOAT, an office building designed by architect Renzo Piano, was built at the southern end of Dusseldorf’s so-called “Medienhafen” (media harbour) in Germany. This building has now been connected to the “Capricorn” building across the street by a spectacular steel-and-glass pedestrian bridge designed by Gatermann + Schossig Architects.
The impressive, 35-metre long pedestrian bridge looks like a glass diamond. The unusual shape of the bridge is created by the polygonal arrangement of trapezoidal and triangular insulating glass units. The construction was realised by façades specialist seele.
Cover Image: CF Toronto Eaton Centre Bridge, a circa. 35m long pedestrian bridge, spans over Queen Street West between the Hudson’s Bay building and the CF Toronto Eaton Centre in the heart of the Canadian metropolis of Toronto. Photo credit: ©Sight on Site Inc
One Bridge With Different Angles
The bridge structure, with a total length of 35m, consists of a closed, tubular grid shell with glazing made of circa. 60 trapezoidal and triangular insulated glass units (up to 8.1m x 3.0m). The kink in the bridge, evident in the horizontal section, ensures an exact connection to both buildings. The loads of the bridge are absorbed solely by means of the steel structure in the glazed middle column. Since the two cantilevered bridge arms to the left and right of the column have different lengths and angles, the structural design is correspondingly complex.
In terms of structural design, the Capricorn bridge is demanding: One main challenge is that the bridge structure is not supported by the connected buildings. The supporting structure consists of a central pylon and two bridge arms. The load is transferred to the central pylon at the point of the bridges ascent, with the concrete base plate itself, resting on three drilled piles. The central pylon consists of 13 round columns. The base of the pylon, the so-called base unit, was delivered to the construction site in one 8m x 3m piece and was encased in concrete. This is why the column footings were already in their fixed position in the factory. Absolute precision was required, because every millimetre was decisive for assembly on the construction site.
Complex Steelwork And Structural Engineering
The bridge body consists of a closed tubular grid shell with ribs and transversals. Even the support structure of the bridge is built from a grid shell. Eight steel polygons, longitudinal ribs and diagonals form the steel structure for the precision fitted insulating glass units. The dead load of the structure was included in the static analysis as well as the wind load, snow load and the deformations from the payload on the cantilever arms and the vibration behaviour. The loads of the bridge are transferred exclusively by the steel structure within the central support, which is also glazed. The shape-forming steel construction of the Capricorn Bridge was manufactured by seele pilsen in the Czech Republic.
Semi-transparent Glass Shell
The glass shell of the Capricorn bridge consists of circa. 60 individual glass elements in sizes of up to 8.1m x 3m. In detail: 35 insulating glass panels, 17 opaque laminated safety glass panels and 5 glass panels. In particular, the trapezoidal glass panels with acute angles of up to 34.9°, partly with recesses for the supporting structure, are very striking. The insulating glass consists of two laminated safety glass panes, each consisting of 2 x 10 mm heat-strengthened glass. A dot-matrix of white print on face 2 fades to the viewing height and later forms the reflecting surface for the bridge lighting.
One particular challenge of this project was the demanding installation procedure of the steel structure. Due to the bespoke design of the bridge, the 7t steel structure had to be adjusted and aligned with the greatest precision. After the successful positioning, 10 tons of reinforcing steel were braided at the base and encased in concrete. The central pylon now forms the connection for the steel construction. Thanks to a perfectly coordinated logistics and assembly concept, the two cantilevers weighing 26 and 12 tons respectively, were lifted and fixed in just one weekend. The cantilevers of the bridge each consist of two half-shells, which were pre-assembled on site. The lifting into the final position was carried out as a whole, with the installation of the steel frame being followed by the glazing of the bridge body. Following completion of the work, the bridge protrudes freely from the central pylon 12m to the Capricorn building and 20m to the Float building.
Other Examples of Bridge Constructions: The CF TEC Bridge, Toronto/CAN
With a total length of 35m, a complex shape and sophisticated supporting structure as well as special glass sizes and geometries, seele once again proved its expertise in bridge construction.
Three years ago, seele was commissioned to design, construct and install the CF Toronto Eaton Centre Bridge, a circa. 35m long pedestrian bridge, weighing approx. 200t. Located at third-floor level, it spans over Queen Street West between the Hudson’s Bay building and the CF Toronto Eaton Centre (CF TEC) in the heart of the Canadian metropolis of Toronto. seele handled the demanding installation procedure on Toronto’s most important shopping street with a sophisticated design and logistics concept.
The old bridge between the two buildings had to be removed and the new bridge installed within an exactly defined time-slot. The CF TEC Bridge was completely pre-assembled just around the corner on James Street. This included delivering the primary and secondary steel structure, glass, commercial bronze plates and all further components to James Street for assembly there on temporary staging. Following this, the bridge was raised hydraulically with the help of a modular vehicle and transported to its final position on Queen Street West, ready for lifting into position. The scope of seele’s work covered the design, fabrication and erection of various panes of laminated glass, commercial bronze plates, handrails, stainless steel open-grid flooring and structural steelwork. Given the challenging shape of the steel-and-glass design, every commercial bronze plate is a one-off in terms of its geometry and the milling work required.
For both projects, seele demonstrated its expertise in the field of filigree steel-and-glass structures along with the requisite time sensitive erection procedures for bridge constructions. In order to construct free architectural forms with glass, designs are created as detailed, complex 3D models. During the planning process, multiple structural and performance calculations must be factored and considered and this high level of engineering competence facilitates the reduced visibility of supporting structure, thus enabling glass to take centre stage, as the dominant façade material.
This article was originally published in IGS Magazines Winter 2020 Issue: Read the full Magazine here for more thought-leadership from those spearheading the industry
Author: Andreas Hafner, Managing Director at seele GmbH and seele (UK) Ltd
Andreas Hafner is Managing Director at façades specialist seele, one of the world’s top companies specialising in the design and construction of façades and complex building envelopes made from glass, steel, aluminium, membranes and other high-tech materials. With over 25 years of experience in the field of façade engineering.
Andreas has already been involved in numerous projects all over the world. In his role as Managing Director, Andreas Hafner is responsible for general management including strategic development of business, sales and new technical approaches within the seele group. Together with his team he realised well-known façade projects in Europe and North-America, such as the Strasbourg Railway Station (France), King´s Cross Station (UK), the TEC Bridge (Canada) and the Museum of Westward Expansion at Gateway Arch (USA).
Main Contractor: Pirol Holzstraße GmbH & Co. KG
Architect: Gatermann + Schossig Architekten GmbH
Engineer: osd – office for structural design; Wilhelm & Partner