Viewing Tower in Stuttgart

Sixteen years ago, the city of Stuttgart was chosen as the venue for the International Horticultural Show 1993. For financial reasons, the winning design in the competition for a viewing tower was not realized at that time. Now, eight years later, donations and subscriptions have enabled it to be built. At the centre of the tower is a slender compression mast with a hinged seating. The mast is 41 m high and 50 cm in diameter. Suspended between the mast and the surrounding network of 48 finger-thick cables, are four viewing platforms. A double helical staircase for separate ascent and descent provides access to the platforms. The tower is designed to bear the load of 2,230 visitors. The network of cables is spanned to its full diameter by a “wreath” or compression ring suspended from the mast by radial cables. The diagonal cable net is fixed in waisted form between the compressing ring and the heavy foundation ring. The four decks brace the towerin spoke-like manner; they also restrain the mast and divide its length in respect of buckling. In view of the large radii of curvature of thenetwork, cables with a great length of lay – and thus a high tensile strength – can be used,which ensures that the platforms are rigidly fixed. The small amount of deflection ofthe cables permitted the use of larger strand cross-sections, which exhibit only a small loss of bearing strength when anchor clips are attached.