The 135 000m2 site is situated in Croydon in Cape Town and is bounded by the R102, the Eerste River, the railway line bordering Stellenbosch and the Steyne Road. The Corruseal Group propose to construct a world class facility for the manufacture of corrugated cardboard for local industries. Their requirement was a factory/warehouse of approximately 30 000m2 and associated offices of approximately 500m2 on two levels. The factory/warehouse was to have a width of at least 150m and was to allow for future extension. The eaves height was to be at least 6,5m.
The first challenge was to determine the overall shape of the structure. It is this engineer’s opinion that the basic format of the structure should be determined by the engineer to achieve the most economical and efficient building. Due to the overall size of the building, the most efficient roof structure was determined to be a barrel vault. A double pitched roof would have resulted in an unnecessarily high apex with concomitant high gables and a significant increase in the quantity of steelwork and sheeting. Costs of services too would have increased. Valley gutters were not considered to be an option because of the potential for roof leaks. A distinct advantage of the barrel vaulted roof is that when the slope is very flat rainfall runoff is negligible, but when the runoff is at its maximum, the slope is at its steepest.
An extremely large radius of 600m was selected for the curve of the roof for aesthetic as well as functional reasons to limit the height of the crown of the roof to reasonable proportions. Natural lighting was introduced through the use of monitors which also enhanced the general aesthetics of the structure. Secret fix Klip-tite sheeting was selected for its slightly deeper profile and its advanced clipping system. Sheeting was kept to manageable lengths by dividing the curve into three approximately equal sections, with the middle sheet raised by 80mmto avoid a butt joint at the crown where slopes were extremely flat.
The curve of the roof made the use of cellular beams an obvious choice because of the ease of introducing a radius to the rafters. Cellular rafters were selected also for their aesthetic appeal and their elegant proportions.
The second challenge was to determine column centres which would accommodate Corruseal’s large manufacturing plant, operating system and warehousing requirements. Through a process of trial and error, the optimum grid for the structure was 6,75m in both directions. Columns were fixed at 20.25mx13.5m centres with the curved cellular rafters spanning the 20,25m dimension and transverse parallel chord girders spanning 13,5m. The overall size of the building (centre line to centre line) was set at 162x162m.
The structure was initially designed using steel columns. However when it came to determining where to locate internal vertical bracing, every position selected clashed with Corruseal’s operation and reinforced concrete columns were the only alternative. This decision led to the columns being precast which helped to reduce the overall duration of the project.
For functional and aesthetic reasons cantilever rafters were introduced at the eaves. This will ensure that rainwater will be discharged away from the sides of the building in the unlikely event that the gutters will be overtopped. The cantilevers would obviate the truncated appearance on the sides if they were left off.
Detailing of the steelwork was achieved using Tekla software which ensured that only a few minor issues had to be dealt with on site.
|Tons of structural steel used||596 TONS|
|Structural profiles used||CURVED CELLULAR BEAMS & STRUCTURAL SECTIONS|
|Cladding profile/ type used||KLIPTITE 700 AZ 200 ZINCALUME 0.53|
|Cladding area/ coverage and tonnage||30000m²|
|Project Team Role||Company|
|Nominator||Macsteeel Service Centre SA|
|Client/ Developer||Corruseal Group|
|Structural Engineer||Alan McNaughton & Associates|
|Main Contractor||JNM Construction|
|Steelwork Contractor 1||Avellini Bros (Pty) Ltd|
|Steelwork Contractor 2||Union Steel|
|Steel Erector||Union Steel|
|Cladding Manufacturer||Blue Scope Steel|
|Cladding Supplier||Global Roofing Solutions|
|Cladding Contractor||Chartwell Roofing (Pty) Ltd|
If you were a part of this project, and your company details are incorrect or missing – please notify the SAISC so that the error can be corrected.