This article is part of our new "Material Focus" series, which asks architects to elaborate on the thought process behind their material choices and sheds light on the steps required to get buildings actually built.
Installed last year, the Salling Tower provides a striking, sculptural landmark in Aarhus Docklands. From inside, its deceptively simple counterbalanced form provides a range of ways to look out over the harbor and the city - but from the outside the project's designers, Dorte Mandrup Arkitekter wanted the tower to take on an abstract appearance, referencing nautical themes with its sail-like shape and porthole-like openings all while obscuring the process of its own construction. To do this, the firm created a structure composed entirely of a single steel piece resting on top of its foundations. In this interview, project architect Noel Wibrand tells us about how the project's material choice contributed to the construction process.
What were the principal materials used in the project?
The viewing tower consists entirely of steel plates. Sheets vary in thickness from 20 to 30 millimeters. The construction is welded into one piece, which was mounted on a concrete foundation in a counterbalance structure. All steel parts were painted with a white paint used in the off-shore industry.
In terms of materials, what were your biggest sources of inspiration and influence when selecting what the project would ultimately be made of?
The viewing tower is conceptualized as a huge “origami” structure, and the picture of a piece of folded paper was used as design criteria in the tender and detailing phases.
Describe how material decisions factored into concept design.
The challenge in this design was to maintain the original idea as well a keeping the abstract feel of the design. The detail design process was very much about reducing and simplifying the detailing.
A very large part of the design resources was put into calculating loads and stability for the tower. With its many tilted faces this required a good amount of technical knowledge and skill with computer simulations and calculations. Søren Jensen Engineers provided a sound a professional expertise at this.
What were the advantages that this material offered in the construction of the project?
The advantage of using a homogeneous material, and having no climatic shell or requirements is that you actually can obtain a simple and light structure. The holes in the tower also helps reduce windloads and create a 20% reduction in material, along with freedom to place openings towards views of the city. The tower itself weighs approximately 85 metric tonnes.
Were there any challenges you faced because of your material selection?
Another challenge in the design was to connect the very small “footprint” of the tower with foundations. Even though the old harbor front has been used for loading cargo onto ships, the documentation for this specific construction required thorough investigations.
Did you consider any other possible materials for the project, and if so how would that have changed the design?
We did considering a lighter construction, with metal sheets on a rib structure. This alternative would have been much lighter, and easier to calculate and build on site, but would have resulted in a much less elegant design, as well as a less spectacular mounting process. One function of the tower was also to create an event to put attention to the development of Aarhus harbor.