The Mpumalanga International Fresh Produce Market in Mbombela was constructed for the Mpumalanga Economic Growth Agency to act as a regional catalyst for growth, creating jobs and improving food security. Serving the local and international food industry, this so-called ‘market of the future’ is also the Steel Awards 2023 overall winner, winner of the factory and warehouse category, the tubular category and recipient of the Best Project Mpumalanga Award.
Project brief
The entire project consists of 17 buildings, each playing an integral part in the market operations. Addressing the needs of the modern food industry, the facility is designed to operate more effectively and efficiently than existing, traditional fresh produce markets.
True to the saying, ‘form follows function’, the design of the main market building aims to accommodate the most flexible market operations. Possible future alterations and expansion to these operations were considered through the following interventions:
- Extruding the roof design to the back.
- Current gridline numbering runs numeric from the top to the bottom, to ease and consolidate future design extensions with the current design.
- Sail material roofing at the back of the building connects lightly with the back-end gable, which will allow flexibility for future expansion.
Roof design philosophy
The steelwork roof covers a 29 000m² floor area, 220m x 135m. Designed to provide the maximum usable floor space with minimal support columns, an arched roof was used along the entire 220m length, supported at each end using a structural framing system.
This was done with three-dimensional, triangular tubular arch trusses spanning the 220m length with two rows of support columns spaced at 68m. The operator thus has the required flexibility to set out the most productive operational equipment layouts. The side-end supports for these trusses were integrated into the design of the building to accommodate mechanical equipment, and form the support structure for the insulated panel envelope of the building that houses insulated sectional doors that open onto the side platforms.
Fabrication
The main challenge on this project was the sheer size of the roof structure and its structural framing system. This was due to the significant logistical challenge and costs of transporting the roof to the site 330kms away from the fabrication shop in Kempton Park, Gauteng. A decision was therefore made very early during the tender preparation phase to make the entire structure in a modular form, allowing the transport loads to be maximised.
How to manufacture the trusses into smaller piece components took some innovative thinking, particularly regarding how to make suitable jigs to ensure all the components would fit together correctly when assembling them on site.
Materiality
No internal columns for a 30 000m² roof coverage is unprecedented. The only construction material that could have been used to achieve this was structural steel. Its high strength-to-weight characteristics and the ability to assemble such lightweight elements of steel in a structural configuration made it the ideal material.
Translucent modular sheeting to the southern sides of these concrete portal gables allows natural light to enter the building without excessive heat transmission. The roof sheeting consists of a sandwich panel of 135mm insulated material, with sheeting to the top and bottom to maximise temperature control within the building.
Erection and installation
The roof is split into three equal segments for sheeting separated by gutters. Each 68m-long roof sheet was rolled on site and pushed up a scaffold ramp onto the roof.
With eleven trusses in its length, three truss spans over its width and seven truss segments in each span, it was extremely important to ensure quite early in the fabrication process that when assembled, the full trusses, totalling 231 truss segments, would provide the correct dimensional profile to accurately fit into the roof on site.
Assembly of the toblerone trusses on the site necessitated the provision of several assembly frames, which had to be set out, lined and levelled to ensure the accurate assembly of each truss before hoisting. The trial assembly at the workshops proved invaluable to the installation on site.
Project team: “We envisaged a Meccano set and made it work in this magnificent roof structure.”
Project name: Mpumalanga International Fresh Produce Market.
Architect: Orbic Architects.
Main contractor: Enza Construction.
Steelwork contractor: Tass Engineering.
Tonnage: 1 537 ton.
Cladding tonnage: 222 ton.
Roof cladding area: 30 000m².
Side cladding area: 6 200m².
Full acknowledgement and thanks go to https://www.saisc.co.za/ for the information in this editorial.
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