Commerzbank-Arena, Frankfurt, Germany

Professor Manfred A. Hirt, President of the International Association for Bridge and Structural Engineering (IABSE), presented the 2007 IABSE Outstanding Structure Award to the 'The New Roof of the Commerzbank-Arena, Frankfurt, Germany' on September 19, 2007. The Award Presentation took place at the Opening of the IABSE Symposium 'Improving Infrastructure Worldwide – Bringing People Closer'.

The New Roof of the Commerzbank-Arena, Frankfurt, Germany completed in 2005, receives the Award for being a 'a new, elegant lightweight roof over a rectangular stadium with cable trusses, tension and compression rings, a fixed glass fibre membrane and a retractable central polyester membrane which magically retracts to the video cube for storage'.

The Diplomas were presented to the Structural Engineers 'Schlaich Bergermann and Partner' and 'Krebs and Kiefer'; the Architect 'von Gerkan, Marg and Partner'; the Contractor 'Max Boegl Bauunternehmung' and the Owner 'Waldstadion Frankfurt am Main Gesellschaft für Projektentwicklungen'.

The New Roof of the Commerzbank-Arena is a lightweight roof structure consisting of three major parts:

- The outer edge panel carrying the compression ring
- The fixed main roof using radial cable trusses
- The retractable inner roof supported by radial cable trusses

In the roof plane, the structure makes use of the spoke-wheel principle. However, in order to adjust the roof geometry to the outer edges of the stadium bowl, the ideal form of a circle had to be altered towards a more rectangular form. Fourty-four pairs of radial cables are connected to the compression ring. These radial cables are spread vertically, to achieve an out-of-plane stiffness of the roof.

The cable structure for the inner roof follows the same principle. However, the thirty-two radial cables trusses are stressed towards the central point of the system. The retractable roof is stored centrally above the video cube. The membrane can be unfolded by pulling its outer edges towards the lower tension ring. Hydraulic cylinders introduce the necessary prestress to the membrane in its final position.

This spectacular closing process takes only 15 minutes. The world's largest 'convertible' is a perfect feature to improve spectators’ comfort.