An update on a previously reported project
in Aachen, Germany.
By Mark Zeh
Recently, the “Rescuing Hand” helicopter landing platform at the University Hospital Aachen was named “Building of the Week” by the German e-magazine german-architekts.com. This striking structure, designed by OX2 Architekten of Aachen, Germany, marries a wide variety of construction technologies and materials in its form, with membrane technology taking prominent place. I had the opportunity to talk with Marcin Orawiec, one OX2’s founders, about some of the design decisions and construction challenges the firm faced to create this structure.
Mark Zeh: The helicopter landing platform exhibits several different surface materials and fabrication techniques. How were they selected?
Prof. Marcin Orawiec: The funicular portion is clad in duraskin® B18039, a PTFE-coated glass fiber material from Verseidag-Indutex GmbH. We selected their material since it’s one of the very few that is both fire class A2 rated and capable of resisting the high tension under which the membrane is placed. The green passage portion of the structure is clad in steel as we were not able to print the pattern and color combination we’d designed onto this type of membrane. The pattern and color play are based on the interior floors of the clinic.
MZ: The membrane portion is amazingly free of wrinkles or tension lines.
Orawiec: The membranes are under a very high level of tension—about three tons per meter around the perimeter. The planners for the structure, stahl + verbundbau GmbH, Dreiech, Germany, employed Ceno Membrane Technology GmbH, Greven, Germany, to install the membranes. The installation process was quite involved and took about three months to complete. After the steel construction was complete, Ceno Membrane Technology took very accurate measurements of it, then created the cutting patterns for the mounting rails and membranes. Mounting each individual membrane took about two weeks. During this time, the membranes had to be placed under constant tension, then re-tensioned every two to three days. As a result, the membranes relaxed about 1.4% (20cm over a 14m span). At that point, they had reached a point where they could be permanently mounted.
MZ: How did you go about formfinding?
Orawiec: We created the initial form, using Rhino software, then sent it to the engineers for evaluation. A series of these iterations took place before we reached agreement on the final form of the structure. We’re satisfied to say that the result is 98% of our original proposal.
The helicopter landing platform was opened for service in July 2011. Construction costs were 7.5 million euro.
Editor’s note: This project was first reported in FA by Mark Zeh in the May/June 2010 issue.