On the Southern side of the Teutoberg Forest, in the small town of Halle, is one of the best tennis stadia in Europe. The 13 500 spectators and the tennis players need no longer worry about rain, but can still feel that they are sitting in a covered court.

Above them is a transparent roof with a total area of 7000 m2. While the sun shines, the roof is left open above the court. If it starts to rain, however, the roof can close in just 1,5 minutes; play can continue.

Two rings with a box section profile run around the whole stadium. The rings are held in position by a total of 22 vertical stanchions.

The cable system is tensioned between these two rings and the inner steel cable. It supports both the translucent roof above the spectators as well as the transparent internal roof. This roof construction is supported on four vee stays at the corners.

The cables at the four corners have a greater tension than the cable on the straight sections. The opening thus has a square shape. The inner steel cable has a continuous tension of 4600 kN.

The connection between the vertical stanchions and the two outer rings must not be rigid. This would lead to additional transverse forces in the structure. Bearings are therefore fitted at these points which have the following characteristics:

• they permit swivel motion about all axes

• they are maintenance-free

• they can support high loads.