Architects:Renzo Piano Building Workshop
Structural Engineers:Ove Arup & Partners
This is one of eight stadiums constructed for the World Cup held in Italy in 1990.
The spectator seats, which form an oval, were built by assembling on the site 310 crescent shaped precast concrete beams. The upper spectator seats are divided into 26 enormous “petals”. The slits between the petals make the building seem lighter and point out circulation areas, facilitating entry and exit and assuring safety for spectators, Computer simulation assured a clear field of vision foe all seats. To protect the spectators from the hot sun and rain, a PTFE coated glass fiber roof membrane was designed in collaboration with Ove Arup &Partners.
The principal structural members of this roof are box-shaped beams cantilevered from the top of the upper spectator seats, and the secondary members consist of a truss on the front edge of the roof to support floodlights and a truss assembled from steel tubular arches and cables. The result assures the entire membrane surface will be under fension. To make certain that neither games nor spectators are disturbed by strong winds, wind tunnel experiments were undertaken at the Department of Aeronautical Engineering, Bristol University, using several of Srup’s computer programs(such as the Fablon Program and the Gerneral Structural Analysis Program),and design was carried out with great care.(Shunhi Ishida, Renzo Piano Building Workshop)
The roof consists of 26 large panels that individually cantilever from the concrete framework of the upper seating tiers. Between these are smaller panels which act as “structural springs” and close off the large slots between the upper seating tiers. The total are covered is 13,250m2.Although the elevation of the roof are constantly changing around the stadium, a degree of geometric repetition and systematization was achieved for the manufacture of steel framework.
The cantilever span varies from 27m to 14m and at the edges of each roof panel are curved tapered box beams fabricated from steel plate. These are in effect a direct continuation of the concrete framework of the upper tiers.
Linking the tips of these cantilevering box beams are a series if “U”-shaped trusses.these support the stadium floodlighting and provide an access route all the way round the whole roof. Each roof panel is further subdivided by 3 slender arch ribs which span between the back of the concrete stand and the “U”-shaped truss. To obtain extreme slenderness in these ribs their “in-plane” stiffness is enhanced by a fan of tie-rods emanating from each end.
Each roof panel in effect is a rib cage over which a prefabricated membrane panel can be stretched. Each membrane is clamped down continuously on all 4 sides and held in contact with the 3 internal ribs by the biaxial prestress if the membrane and the presence of an external hold down cable between ribs. These cables proevent the membrane lifting off the rib in the worst cases if wind loading .
The geometry of the membrane was defined as an equal biaxial stress field and each panel installed within 408kgf in both directions Ove Arup & Partners also produced the cutting patterns on behalf of the contractor.