Architect and Builder Magazine South Africa Dec 2017 / Jan 2018 - Page 47

demolished to make way for six new suspended concrete art display floors whilst carefully retaining the delicate existing and deteriorated external fabric of the silos, the other half of the internal silos, the future open atrium, required an intricate ‘bite’ to be carved out in the shape of a huge corn grain. What silo proportions remained above the ‘carved’ out atrium actually hung suspended in the air and open to the skies above, but glazed for weatherproofing. To achieve the ambitious atrium carving, the original silos were re-sleeved with new reinforced concrete rings, linked together through the existing concrete rings at strategic positions, to create a structural ‘portal frame’ spanning over Zeitz Mocaa 20m of the atrium. The structural design modelling, sequencing, as well as the geometry of the carving was highly complex. Structural Engineering – Silo Hotel The rectangular Silo Hotel building, being considerably taller at 67m (the tallest building in South Africa at the time of completion in 1924), consisted of a structural steel frame, clad in concrete with reinforced concrete slabs and had no seismic resistance – being originally designed as a grain elevator and storage building, alongside the silos. To be converted to residential use, City of Cape Town building regulations 47