Concrete innovation
Comprising 135,837m² of covered space in 20 buildings, the Shoprite development represents one of Africa’s largest and most technologically advanced distribution centres. Tilt-up concrete columns were used as the main structural element on the three largest warehouses which span a total roofed area of 104,084m².
These comprise:
- >75,000 m² dry-goods warehouse
- 34,735m² refrigerated building
- 10,547m² returns centre
- The dry goods building features two safety stores of about 1,100 m² each which were designed to contain a fire for two hours, thereby protecting the surrounding infrastructure.
Tilt-up describes a construction technique in which predominantly vertical concrete elements such as columns and walls are cast flat on the ground and on site, near their final position. Once cured, they are hoisted into position. By contrast, more traditional precast concrete elements are cast off site and must be transported to site.
- Some of the columns were 26.56m high, SA’s largest precast tilt-up to date.
- Each column weighed up to 44 tons each.
- 148 columns were used to build the main warehouse.
- 39 columns were deployed in the construction of the return-goods building.
- Tilt-up panelling comprising 48 panels and covering a total area of 4,155m² was used in the assembly of the safety store’s external walling.
Structural steel foresight
For WSP in Africa, structural steel was the natural choice to realise the large open span roof structures and curved architectural features of the new facility. The operational design required a 32x32m internal grid for the ambient warehouses and 24x24m for the refrigerated warehouse. No construction material other than structural steel could achieve the same construction economics for these lightweight, large-span roof structures under the given programme constraints.
The design of the buildings and the subsequent construction methodology were all centred around safe and fast erection on site, delivering a light yet failure-tolerant structure. The buildings are stabilised by large cantilevering concrete tilt-up columns that were constructed during the fabrication period of the steel.
- The girders were built-up from horizontally orientated UB chords laced with double equal angle web members. This configuration allowed optimized utilisation of the material and produced a girder that was easier to handle on site due to the lateral and torsional stiffness of the box-shaped assembly.
- The trusses for the ambient warehouses were classic lattices made from equal angle chords and web members. To provide a flat fixing surface for the refrigeration panels, the trusses for the refrigerated buildings were also boxed lattices with channels as chords.
- The connection design and detailing, especially for the girder-to-column and truss-to-girder nodes, also aimed at a reduction of risk during the erection process.
The appointed specialist steel contractor, Mazor Steel, delivered 2,963 tons of structural steel on time and to highest quality standards following a strict safety plan under constant scrutiny by main contractor, Stefanutti Stocks, who achieved over one million lost-time injury free man-hours on this project.
The size of the building and the resulting rainwater run-off lengths of the Dry Goods building supported the choice of a curved roof structure for these buildings. As a result of the curve, the roof angle increases with increasing run-off length, thus improving run-off performance of the roof.
The project was completed on time and within budget while impressing with outstanding design and way-leading quality of works.
