Wolfsburg, Germany, 2013
GRAFT, Berlin; WES LandschaftsArchitektur, Hamburg
Kardorff Ingenieure Lichtplanung GmbH, Berlin
Ingenieurpreis des Deutschen Stahlbaues 2015
Eiffel (Stahlbau/steel construction); Taiyo, formTL (Membrane)
conceptual design, construction design, technical spots check
If there is an external load acting perpendicular to the surface (like wind pressure or suction) the equilibrium state of planar nets,such as vertical or inclined cable net facades, can only be reached through elastic elongation. These strains can be "anticipated" and thus reduced by pretension because the equilibrium state is reached at an earlier point of deformation. Still, there will be increasing deformations towards the center of the net.
Membrane and cable net do not only follow the same anticlastic shape. They are also both similar in set-up and load-bearing behavior since their layers are made out of tension members which are woven or rather knotted in an orthogonal alignment towards each other (compare suspension/tension ropes with warp and weft directions).
This factor carries a certain advantage: Since the offcut of the membrane is generally defined by its orientation within the structure's final shape, it can be minimalized as long as the seam layout follows the orthogonal cable lines, which was wanted in any case.
The roof, a membrane-covered, self-anchored cable net with a dead load of only 8.3 kg/m² covers an area of 1610 m². The edge beam has a total length of approximately 150 m and is symmetrical to the longitudinal axis of the oval layout. The section consists of a welded pentagonal steel box (S355) which undulates and rotates along the longitudinal axis of the edge beam. Thereby the sheet dimensions vary continuously and cause a light and dynamic appearance despite weighing 150 t in total.
The cable net consists of two series of open spiral cables that are aligned orthogonally towards each other with a total cable length about 2100 m. For structural reasons the diameter of the concave-oriented suspension cables (24 mm) varies from the tension cables (20 mm).
It was a guiding principle of Graft and schlaich bergermann partner during the interactive design process to keep the complex structure plain and simple by means of structural clarity in concept and detail.
Main characteristic features of the structure are the plainly visible cable net and the dynamic shape of the edge beam carried by two supports only.