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In
order to protect al grandstands of the Outdoor Stadium against
sun and especially against rain, a cable/membrane roof structure
was built and handed over in 1998 which covers the protected
area column-free, presenting a roof surface of 380000m2.
It became the biggest membrane structure of its type in the
world. The roof is supported along. Its rear edge on the
grandstand concrete structure, and has a cantilever length of
62m constantly all around.
The main structure consists of 36 cable trusses which run
in radial direction between outer steel compression ring and two
inner cable tension rings, which prestress the cable trusses
.The outer compression ring is a steel tube of 1400mm diameter,
which tests on 36 V-shaped columns. These columns resting on the
concrete structure are slightly inclined outwards, and are
hinged at both ends in order to allow a nearly restraint-free
radial movement of the ring.
The radiant cables are stressed
against each other by
suspender. The radial and inner tension ring cables are
locked-coil ropes of large diameters up to 100mm. The vertical
distance of 20m between the two tension rings is secured by 36
steel column struts, pin-connected to cast steel nodes
connecting radial and ring cables.
The whole system of cables and steel ring is prestressed
such that under all frequent wind and other loads, the whole
structure remains under tension, and thus remains stable.
The primary cable structure is covered by membrane panels
which are supported by steel pipe arches, spanning from cable
truss to cable truss. In between these steel arches, the
membrane is saddle-shaped, a condition which under nominal
prestress already guarantees a highly stabilized surface.
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