Architect and Builder February/March 2019 | Page 42

pods to be as open as possible, embedded in the
glass. These pods are also cantilevered from the
concrete frame. The atrium structure formed part
of the glass façade, spanning over six stories and
additionally it formed a part of the glass skylight
structure on the atrium roof. The structure spanned
large distances and had to be as slender as possible
while limiting deflection.
Atrium Structural Engineering
The inner–and bottom chord of the atrium
vertical truss and roof truss were determined by
architectural constraints. The outer chord is braced
by transom beams for the façade glass, however,
the inner chord had a large unbraced length due to
the omission of regular knee-bracing. Similarly, the
bottom chord had a large effective length for the
uplift load case, due to knee bracing not being able
to pierce the bulkheads of the skylights butting
up snug to the truss either side. This resulted in a
relatively large PFC inner chord and large I-section
for a bottom chord. The purlins (bracing for the top
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chord) of the roof had to step, due to the skylight
glass line and sheeting line being on different
levels. Additionally, the purlins form part of the
skylight substructure. The load path was fairly two
dimensional and an RHS section was used. For the
atrium glass transoms, large SHS were used due to
the wind, and gravity load cases being very similar
correlating the sections’ similar radii of gyration in
each direction, it was also aesthetically preferred.
Smart Lighting Installation
Thanks to a unique collaboration between Paragon
Architects, the building owners and digital display
services company, Primary Colours, Rosebank
Link now features a dramatic full-colour RGB
video screen that has been custom-designed to
be an integral part of the building’s fabric, and to
contribute to the building’s striking appearance.
The installation features two distinct elements.
The first of these is the LED screen, which is
noteworthy for being one of the largest in South
Africa. The second is the strip screen display
Rosebank Link