Architect and Builder November/December 2018 | Page 71

ARCHITECTURAL CATEGORY WINNER
Discovery Head Office
Discovery’s Head Office in Sandton was conceived
from the inside out. This concept resolves itself into
two large atria around which the open floor plates are
arranged. The atria are enclosed by 2,800m 2 of glazed
roof. Connecting these atria to one another is a central
concourse, within which a stack of escalators links double
volume bridges that stitch the floorplates together.
A key feature of the building is the floating ‘nose’ of
the west tower. To make a statement that fitted with the
scale of the building, a cantilever of 17.5m over 6 floors
was required. This posed a significant structural challenge
that was eventually solved with the introduction of 3
massive concrete beams that project over the length of
the cantilever. The floors are then suspended from these
beams on steel, concrete filled, columns.
Another challenge was the large atrium roofs. The aim
was to provide as much light as possible which meant
the engineering of a bespoke support solution that was
visually unobstructive, but structurally stable. The solution
from the façade engineers is an elegant tension truss
lattice that supports both the weight of the glazing as well
as resisting the up forces created by the movement of air
over the top of the glazed panels.
The Skylight Roofs are probably the most iconic
and interesting structures within the development and
encompass an extremely innovative design concept allowing
them to convey a minimal structural expression of openness.
The major construction challenge presented by the
design was the requirement to effectively pre-stress the
main and secondary trusses post installation to ensure
their bottom chords remain in tension under all loads.
The pre-stress is achieved by the incorporation of light
pull-down bars which were then post tensioned on the
main support trusses after installation, using purpose
made tensioning brackets and permanently installed strain
gauges to ensure correct tensioning was applied.
The Cantilever floating ‘nose’ is a stunning architectural
feature and an engineering marvel which enables the large
cantilevered six storeys to be supported by the massive
post-tensioned concrete beams at roof level.
This steelwork needed to be accurately manufactured
with beams rolled to seven different radii seamlessly
butt welded together to form the perimeter of the floors
which supports the façade. Each floor has five 508mm
diameter CHS columns which are concrete filled and hang
from three massive post-tensioned concrete beams at
roof level.
The façade support structure required a 200x200x4.5
SHS to follow the three dimensional curvature of the
top edge of the buildings. As this member could not be
successfully rolled to the required radii with the required
finish, a purpose made curved SHS was opted for, using
plates which were laser cut to the required radius and
shop welded to form the curved SHS.
The 11 feature spiral stairs create an illusion of stairs
that are ‘falling’ through concrete voids. There were
additional sweep stairs to complete the access to the
Steel Awards
lower floors. Other works completed were the executive
pergola and smokers canopy at roof level, all boasting
subtle curves in plan and elevation. Added to this was
the design supply of the reception green wall spanning
over 6 floors. Each one of the stairs were double box
stingers 600mm deep alternating between glass and
plate balustrades.
Client/Developer: Growthpoint/Zenprop in a JV
Architect: Boogertman + Partners
Project Manager: Morta Project Managers
Quantity Surveyor: RLB Pentad
Structural Engineer – Skylight: Pure Consulting
Structural Engineer – Main Building: Sotiralis
Main Steelwork Contractor: Tass Engineering
2nd Steelwork Contractor: Spiral Engineering
3rd Steelwork Contractor: Nancy Engineering
Steelwork Erector: Onpar Steelwork Erection
Corrosion Protection: DRAM Industrial Painters
Main Contractor: WBHO/Tiber in a JV
Photography: Mike Bagley
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