Introduction

On 15^th May 2004, South Africa, with Nelson Mandela at its head, celebrated her own nation entertaining proclamation for the Football World Championship 2010.

The existing FNB Stadium in Johannesburg was selected to represent South Africa in the whole world. Thus began the challenge to restructure and to widen the stadium increasing its capacity from the initial 80,000 to 90,000 spectators and in the meantime transform the existing into something able to attract the attention. The most significant design was chosen from various submitted proposals. It's the design for which the Soccer City Stadium is now renamed as the “Calabash” (traditional African clay jug) or the “African Bowl” as the symbol able to represent the whole African continent.

The work

The restructuring and amplification work began 2007 with the trust to the association of enterprises between the local Grinaker-LTA and the Dutch Interbeton BV, while the realisation and assembly on site of the steel roof and the covering was submitted to Cimolai S.p.A. of Pordenone, Italy.

The roof and the façade represent the characteristic elements of the stadium both from an esthetical and structural point of view. Such structures were studied, re-projected and realised in Italy by Cimolai S.p.A. in their own workshop of Pordenone.

The covering of the façade, unique in its type, is a mosaic of panels in light fibro-cement in the colour of the ground and the fire while the roof is covered by PTFE membranes in a sand colour similar to that of the surrounding mines.

The steel structure

The global form of the structure, doubly symmetrical to the axes North-South & West-East, is a torus while the plane of the roof follows the rectangular form of the game field. This confers a complex double bending that varies both in height and width of the supporting perimetric ring and the cantilevered roof beams. The supporting perimetric structure is a reticular construction with a triangular section composed of three longitudinal pipes with variable diameter between 710 mm and 910 mm and a thickness between 20 and 40 mm and a series of wall pipes. The pipes were entirely produced in the shop of Cimolai using a press of 6,000 tons. The whole ring is constituted of 32 sections. The individual sections were assembled on the ground and then lifted into position with a crane of 600 tons and connected to one another by bolted joints. The structure leans on 28 supports from which 12 are principals called “Shaft”. Sixty of the roof beams cover the galleries. These structures were assembled on the ground in panels and subsequently lifted into final position using cranes from 300 to 600 tons. The façade is organised in 120 axes and consists of vertical HEA 400 and HEB 400 profiles bent with 3 different bending radii and of transversal RHS profiles.The erection activities on site necessitated the use of a fixed topographical station to control both the exact position in space as well as the general appearance of the preceding sections so that the resulting geometry of the roof complied with the project.

Cimolai S.p.A. won the South Africa Prize 2009 for the best structure in steel due to the complexity of the structure, the quality of the supply and the beauty of the realised work. The opening ceremony and the finals of the football championship 2010 will take place at the Soccer City Stadium.

Main data:

• Weight of steel construction: 8,000 tons

• Coverings: 53,000 m² of PTFE membranes and 40,000 m² of panels in fibre-cement

• Period of transport: from March 2008 to January 2009

• Beginning-end of the erection of the steel structure on site: June 2008 – March 2009

 
With the kind authorization of Cimolai S.p.A.