The Marc, an acronym for Maude and Rivonia Corner, has transformed the prestigious intersection in Sandton formerly occupied by the Village Walk shopping centre. Bob van Bebber from Boogertman & Partners took the opportunity to make a statement on the Sandton skyline with the use of colour. The highly impactful black and gold façade of Tower 2 (the Jewel) articulates the intersection like a glittering jewel.
Generous pavements, public benches and sculptures create an accessible urban space with no barriers, while ensuring safety and functionality. The walkability of the precinct encourages the use of public transport and mitigates congestion in the commercial hub of Sandton.
Grand stairs punctuated by urban artwork, in the space between the two majestic Towers, where the Jewel unfolds between the crystal façade of Tower 2 lobby and the Atrium with glazed canopy, lead pedestrians from road level to the retail section covered by the skylight.
Arup Façade ‘zengineers’ were involved in June 2015 in the development of the Village Walk site. The façade team worked closely with the developer Eris, the Architects Boogertman and Partners, structural engineers Aurecon, Mechanical Engineers Spoormaker and Partners and Quantity Surveyors AECOM, to assist with the façade design for the two towers and retail skylight for this prestigious mixed-use development.
Tower 1 is an 18 storeys mixed-use building. The envelope consists of a flush glazed curtain wall. Located at the lower ground floor, Tower 1 entrance lobby is a triple volume glazing enclosure set back from the curtain wall above. The double glazing aluminium framed panels are supported onto steel fins moment fixed at the underside of the second floor slab and connected by bracing SHS steel members. The glass panels are curved at the north-east and north-west corners.
Both Tower 1 façade lobby supporting structures and the retail Skylight were initially conceived as timber structures. Steel was the material chosen in the end for the natural strength and aesthetic honesty. The steel assembly also contrast beautifully with the internal timber slat fit out.
Tower 2 is a rectangular office building which features lower retail floors, and the Jewel, a magnificent skin of gold and black triangular facets interlocked to achieve an elegantly smooth curved shape. The jewel intersects the Tower’s north-east corner and the multistorey glazed Atrium bridges across the rectangular and the curved portion.
The Jewel façade’s surface is formed by a mesh of 5620 alternating gold and black flat triangular elements, flush glazed onto aluminum framing. The Jewel’s surface, generated by symmetric double spirals in plan, was coded in a parametric environment, allowing the geometry of the spiral curve to be adjusted to change the overall shape of the façade ensuring to maintain geometric relationships that provide the smooth curvature while maintaining the geometric rigour that facilitates fabrication.
The retail space occupies the lower floors of Tower 1 and 2 and the space between, covered by a glazed skylight.
The Jewel’s steel backbone The structural scheme for the Jewel’s façade was realised at a team brain storming session at one of our daily visits to our favourite coffee shop. The unitised façade is composed of interlocking triangular and diamond-shaped units. In contrast to a typical unitised façade with one panel per floor height, the jewel façade is made up of four interlocking units per floor.
The gold triangular panels are moment fixed at each floor level with steel brackets fixed to top and bottom of slabs.
Diamond shaped units are locked into the golden triangles 5000m^2 of glazing are supported by 58.2 T of steel brackets.
The installation of the whole building had to be completed in only about seven months, which meant that the façade contractor Geustyn & Horak had to complete two floors every month, fitting about 240 triangles in a week.
Geré Sadie, who managed the onsite installation for Geustyn & Horak, said that the team had to reinvent their installation process. “It was a learn-as-you-go process”.
They had to start off by building full scaffolding around the building in order to be able to set out the brackets at both the bottom and top of each slab, each one at a unique point.
Tower 2 lobby
Tower 2 Lobby façade is supported by 13m long 160x80x5 vertical RHS at 2.4m centres, and 80x80x4 horizontal SHS at 1.85 centres (45 kg/m^2). The glazed canopy is made up out of custom tapering cantilevering T-sections.
Tower 2 Atrium and glazed canopy
The 40m high glazed atrium façade that interfaces between the Jewel and the rectangular portion of Tower 2, is supported by a beautiful skeleton of horizontal steel trusses of variable length at 4.05m spacing (TRUSSES: chords 140×5 CHS, truss bracing 102×4 CHS, outer hanger 60mm solid round-selected for its axial stiffness, inner hanger 89×4 CHS).
The series of trusses fixed at the ends to the Tower’s slabs, is suspended from the roof structure above and has been designed to allow for the natural structural deflections.
The external glazed canopy is supported by welded T cantilever beams of variable depths and 60×3 CHS hangers.
The atrium and canopy steelwork weighs 43.94 T.
Tower 1 Lobby
The triple volume glazed envelope at the entrance of Tower 1 is supported by 16m long 400x25mm steel flats at 3.2m centres. The hangers cantilever from the underside of the 2nd floor slab and are braced by 60x60x4SHS sections at 2m centres. The weight of the steelwork per square metre of façade is 27.5 kg/m^2.
The retail Skylight structure consists of variable length (max 15m long) triangular welded rafters of different sizes (min 130hx60w, max 360hx165w) with 160x80x4 RHS bracing supporting double glazing skylight.
|Completion date of steelwork||· Tower 1 lobby-April 2018
· Tower 2 lobby-April 2018
· Tower 2 Atrium+ canopy-July 2018
· Retail Skylight-April 2018
|Completion date of full project||September 2018|
|Tons of structural steel used||· Tower 1 & Tower2 lobbies-40.63 T
· Tower 2 Atrium + canopy-43.94 T
· Retail Skylight-25.6 T
· Tower 2-The “Jewel” glazing brackets-
|Structural profiles used||· Tower 2 Lobby-13m long 160x80x5 vertical RHS at 2.4m, 80x80x4 horizontal SHS at 1.85 centres (45 kg/m^2)
· Tower 1 Lobby : 16m long 400×25 steel hangers at 3.2m centres and horizontal 60x60x4SHS bracing at 2m centres (27.5 kg/m^2)
· Tower 2- 40m high glazed Atrium + canopy: horizontal trusses at 4.05 spacing
TRUSSES: chords 140×5 CHS, truss bracing 102×4 CHS, outer hanger 60mm solid round, inner hanger 89×4 CHS
Horizontal trusses with 26,4m max span, 20kg/m^2 of façade
CANOPY: beams variable depth welded T, hangers 60×3 CHS
· Retail Skylight- max 15m long, triangular welded rafters (min 130hx60w, max 360hx165w) supporting double glazing skylight. 160x80x4 RHS bracing
|Completion date of cladding||Tower 2 the Jewel completed in July 2018|
|Cladding profile/ type used||Tower 2- the “Jewel” glazing support steel brackets:
Alternating brackets top and underside of slabs to support unitised glazed triangular panels
Top bracket: 8mm folded and shaped steel plates
Bottom bracket: welded 127×64 chennel knee bracket with 50x50x5 bracing
|Cladding area/ coverage and tonnage||Triangle and diamond shaped unitised double glazed panels structurally glazed to powder coated aluminium frames.
5000m^2 of glazing supported by 58.2 T of steel brackets