Constantia Emporium is a contemporary convenience and lifestyle centre located in the leafy suburb of Constantia, Cape Town. Located on a land restitution site, it is envisaged that the new retail centre will act as a catalyst for further development on the remaining restitution sites. The centre is anchored by a flagship Checkers, Woolworths, Clicks, two eateries and offices. The ground floor accommodates the upmarket line shops, anchor tenants and eateries, whilst the offices are located on the upper level.
The architectural design was in response to the rural wine making surrounds and rich history of the site, the practical and honest nature of farm shed design was deemed a fitting inspiration for the contemporary architectural language of the project. This dressed-down and hard-wearing architectural style celebrates familiar rural homestead forms and incorporates a layering of materials including off-shutter concrete, steel, glass, slatted timber and profiled steel sheet cladding.
The use of exposed steel features plays a pivotal role in achieving the design aesthetic and forms the basis of nearly all the design elements used to complete the project.
A brief description of the structural framing
The Anchor tenant roof consists of a complex combination system of trusses and girders, which covers more than 3300 square metres. The steel trusses and girders are made up of angle iron members. The truss and girder system was the best design option for this steel structure, due to the large spans and restrictions on the number of supporting H-columns in the trading floor below. The main roof comprises of 3 raised sections with ‘valleys’ separating them. This proved to be a challenge as a conventional truss and girder system could not be used. Instead of connecting in the same plane, the girders were lowered with trusses connecting above it, which makes the structure quite unique. Portions of the roof intersect with and wrap down the large wall, breaking up the elevation along the M3 highway.
The line shop roofs comprise of steel portal frames or rafters. The feature trusses of the main barn roof over the central eatery brings interest and character to the dramatic double volume space. Six pairs of custom-designed crisscross rectangular hollow section (RHS) trusses converge at the roof apex in an elegant bolted plate connection. This is complimented with solid timber cladding, elegant tension cable detailing and delicate dropped ceilings which follow the form of the trusses.
There were numerous special steel elements in the project ranging from exposed steel canopies to timber clad portal structures as well as a suspended steel bridge and the steel/ glass lift structure.
The suspended steel bridge inside the mall is a powerful example of the ability of steel to produce a captivating floating effect. The bridge structure connects the lift shaft structure to the first-floor level. The design intent was to achieve a floating walkway structure with minimal support. The bridge structure consists of a beam and joist system cantilevered from the support columns and suspended from the roof slab above with steel hangers. The challenge here was the extreme detail and accuracy required during construction and assembly. Intensive detailing was required to incorporate the steel handrails along the edge of the walkway
The glass lift shaft is the central feature of the mall. The glazed exterior exposes a carefully detailed internal framework of structural steel H-sections which bring interest to the internal mall space. There was some difficulty in its assembly and erection as the columns in some instances were double volume with lengths of more than 8.0m.
Much of the character of the building is derived from carefully proportioned exposed H-section portals married with finely detailed timber beams and slats. The steelwork was carefully coordinated with the timber with predrilled sections and pre-welded plates. Cladding rails and cladding structures needed to be provided too extreme accuracy and steel angle rails were the most suitable material in terms of durability and strength. The result is understated elegance and sophistication.
The elegant double-height structural steel canopy is the main feature of the entrance façade. Topped with aluminium slats for solar control, the minimalist steel C-section framework cantilevers generously over slender circular steel columns with expressed bolted connections. Stainless steel planter cables reach high up to the frame from the sumptuous planters below and were carefully coordinated to avoid on-site drilling or welding. This feature sets the sophisticated, understated tone of the building. The lower main entrance canopy continues the theme by combining exposed suspended H-section framework with finely detailed timber slats and timber sub-structure.
A brief description of the cladding process
Safintra Saflok 700 was used to clad the roofs and large portions of the facades. The architects colour palette included black, concrete greys and timber. They, therefore, wanted a roof sheeting that was black with no undertone of blue-grey and selected unique finish Colourplus Textured in the colour: Smokey Grey. The textured finish did make handling of the product more complex to avoid scratches and damage during installation. The architects required special flashing details to provide a crisp edge to the roof. The architects also specified that all ribs to the roof sheet were to line up with the ribs to the vertical cladding to create the appearance that the roof wrapped down onto the facades.
Engineering, fabrication and erection
The erection of almost all of the steel elements was challenging due to the high level of precision required. All steel was fabricated in Durban and then delivered to Cape Town for erection. The project had an extremely tight project deadline and there was no time for errors and rework. In some cases, a surveyor had to be called out to assist with the setting out of the high-level steelwork. The holding down bolts, bridge hanger connections were cast into columns, beams or slabs leaving no room for error.
The feature steel trusses over the central eatery were erected with a spider crane that had to be brought up from Durban. The crane had to stand on the suspended ground floor slab and the coordination of the loading with the structural engineer was complex.
This suspension bridge connected the lift shaft with the ablutions and 3 separate office spaces all located on separate portions of slabs cast at different stages of the project, extreme accuracy was required to ensure all the floor levels tied up within the required tolerances.
The project required an exceptionally high-quality finish. The majority of the steelwork was used to create the buildings design features. The steelwork, therefore, needed to be precise not only in its fabrication but also erection.
Impressive technical aspects
The project successfully demonstrates how steel can be used in conjunction with other materials such as timber and glass to create slick, contemporary design features.
The most challenging or appealing use of structural steelwork was the “spider truss-rafters” in the Line Shops Roof 1. These connections at the eaves and apex were more architectural, with more aesthetically pleasing end connections. Furthermore, the marriage between steel and timber is well displayed in this roof by the timber cladding of the rafters. Forming the “spider truss-rafters”, with the use of RHS 250 x 100, shaped fin plates, uc-sections, stainless steel cables and CHS buckle, was quite innovative. It was further complimentary/unique in that the trusses did not span the structure conventionally, but rather straddled across the ring beams like a “steel spider” armoured in timber
How the project team worked together
The sub-contractor produced very detailed IFC models of the steel elements before they proceeded with the detailed shop drawings. This allowed the engineers to visually inspect the models to ensure compliance with the design intent and issue relevant comments early on to avoid any abortive work in the production of the shop drawings. The architects were also able to load these models into the Revit model to check the steel design as well as incorporate accurate steelwork in their drawings and details.
How this project demonstrates the benefit of steel as a material
The project uses a variety of steel members and sizes in different configurations to achieve the architectural design features. The clean lines and bold visual impact of steelwork make it compelling to expose and showcase. Superb compatibility with the use of timber. Further project/construction benefits ticking all the boxes in terms of speed of installation on site (after components are fabricated off-site), speedy adjustments on-site and the inherent strength of steel allowing it to be far more slender than alternative materials.
Project motivation editorials are provided by the project nominator. If any technical details, company names or product names are incorrect, please notify the SAISC so that the error can be corrected.
| PROJECT OVERVIEW | |
| Physical address of the project
Street Address Town Province |
55 Ladies Mile Road
Constantia Cape Town Western Cape |
| Google Maps link |
| STRUCTURAL STEELWORK | |
| Completion date of steelwork | 29 September 2019 |
| Completion date of full project | 26 November 2019 |
| Tonnage and steel profiles used | Steel Columns & Beams – 44,640 t
· 150 x 150 x 4.5mm x 20.64kg/m Square hollow section columns · 152.4 x 4.0mm x 14.64kg/m Circular hollow section columns · 152 x 152mm x 23kg/m H-section columns · 03 x 203mm x 46.10kg/m H-section columns · 305 x 305mm x 97kg/m H-section columns · 160 x 80 x 4.5mm x 16.4kg/m Rectangular hollow section beams · 203 x 133mm x 25.1kg/m I-section beams · 250 x 100 x 4.5mm x 23.8kg/m Rectangular hollow section beams · 300 x 140 x 6.0mm x 39.5kg/m Rectangular hollow section beams · PFC 200 x 75mm x 24.3kg/m beams · PFC 230 x 90mm x 32.2kg/m beams · 150 x 150 x 8.0mm x 36kg/m Square hollow section columns · 200 x 200 x 6.0mm x 35.82kg/m Square hollow section columns · 254 x 254mm x 73.10kg/m H-section columns · 127 x 6.0mm x 17.90kg/m Circular hollow section columns · 203 x 203mm x 52kg/m H-section beams · PFC 200 x 75mm x 24.3kg/m beam · IPE 160 x 82mm x 15.8kg/m I-section columns · IPE 160 x 82mm x 15.8kg/m I-section beams · PFC 180 x 70mm x 21.1kg/m beams · 50 x 50 x 4.5mm x 6.548kg/m Square hollow section columns · 203 x 133mm x 25.1kg/m I-section beams
Steel purlins, girts, bracing – 63,490 t · Round hollow section bracing · 150 x 50 x 20 x 2,5mm Thick cold-formed lipped channel purlins · 150 x 75 x 25 x 2,5mm Thick cold-formed lipped channel purlins · 200 x 75 x 20 x 2.5mm Thick cold-formed lipped channel purlins · Welded bracing, anti-sag rails, etc with flat connection plates, bolted to steel · 100 x 50 x 20 x 2,5mm Thick cold-formed lipped channel bulkhead supports
Steel Trusses – 69,090 t · Lattice steel roof trusses of angle rafters, tie beams, rails, struts, braces, cleats, etc and flat bearer, gusset and connection plates, bolted to steel · Lattice steel roof girders of steel angle rafters, tie beams, rails, struts, braces, cleats, etc and flat bearer, gusset and connection plates, bolted to steel
Steel Rafters – 2,830 t · 24mm x 3.55kg/m Solid round truss ties · 203 x 133mm x 25kg/m I-section rafters · 250 x 100 x 6.0mm x 31.53kg/m Rectangular hollow section rafters · 254 x 146mm x 31kg/m I-section rafters · 305 x 165mm x 40kg/m I-section rafters · IPE 100 x 55mm x 8.1kg/m I-section rafters · PFC 180 x 70mm x 21.1kg/m Parallel flanged channel rafters · 254 x 146mm x 31kg/m I-section rafters · 254 x 254mm x 73kg/m I-section rafters
Steel Gutters & RWDP – 11,090 t · Box gutters 400 / 450 / 500 / 600 / 800mm girth, four times bent along length including necessary collared and sealed expansion joints · 75mm Internal diameter pipes · 10mm Internal diameter pipes · 150mm Internal diameter pipes · 200mm Internal diameter pipes
TOTAL TONNAGE = 192,280 t
|
| CLADDING (If applicable) | |
| Completion date of cladding | 17 November 2019 |
| Cladding profile/ type used | Roof & Side Cladding:
Safintra Saflok 700 – 0.53mm thick Colorplus Textured |
| Cladding area coverage | Roof Cladding: 5842 sqm
Side Cladding: 1703 sqm |
| Cladding tonnage | Roof Cladding: 32,13 sqm
Side Cladding: 9,37sqm |
| Project Team Role | Company |
|
Nominator |
SAFINTRA South Africa (Pty) Ltd |
| Client/ Developer | Shoprite Checkers (Pty)Ltd |
| Architect | SVA International (Pty)Ltd |
| Structural Engineer | DVP INC Consulting Engineers |
| Engineer | DVP INC Consulting Engineers |
| Quantity Surveyor | AECOM (Pty)Ltd |
| Project Manager | |
| Main Contractor | WBHO Construction (Pty) Ltd |
| Steelwork Contractor | Churchyard & Umpleby Construction (Pty) Ltd |
| Steel Erector | Churchyard & Umpleby Construction (Pty) Ltd |
| Corrosion Protection | Churchyard & Umpleby Construction (Pty) Ltd |
| Galvanising | Churchyard & Umpleby Construction (Pty) Ltd |
| Paintwork Contractor | MRH Blasting & Coatings (PTY) LTD |
| Cladding Manufacturer | SAFINTRA South Africa (Pty) Ltd |
| Cladding Supplier | SAFINTRA South Africa (Pty) Ltd |
| Cladding Contractor | Scheltema & Co (Pty) Ltd |
| Corrosion Protection | Scheltema & Co (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.