DUBE SQUARE CANOPY

project team
Developer/Owner:
Dube Tradeport
Architect:
CNdV Africa landscape architects
Structural Engineer:
Henry Fagan & Partners
Steelwork Contractor
STS Engineering
Steel detailing company
PSM
24 Steel Construction Vol. 36 No. 2 2012
PROJECTS
For the tendered scheme a central circular node
was proposed orientated at the average of the six
adjoining planes it connected, with solid infill
ends to the gridshell members machined to meet
the external surface of the node. Bolts with
shaped washers would bolt through from the
inside node to threads in the machined pieces.
With the input of the contractor this concept
was changed to a welded proposal eliminating
the need for the solid machined ends and any
pre-drilled holes in the node. The ends of the
rectangular sections were instead cut to the
profile of the outside surface of the node and
directly welded into panels of nodes in the shop.
To accommodate the various orientations of the
adjoining members, the circular node projects
through the roof surface and is capped with a
circular glass plate. Its internal end is either
capped with a solid infill plate or light fitting.
While at times up to 12m above people’s heads
these nodes are in some way brought closer to
the observer by the shadows they cast at their
feet on the square’s surface.
ERECTION
Piling, pile-caps and plinths were first constructed
for all six support locations with cast-in
anchors for the connection of the base of the
rear columns and oversized plinths recessed
below the final landscape level to allow some
tolerance on position of the ground connections
relative to the concrete works.
The rear columns rise 10 metres above the square to meet the gridshell at the
three rear node connections.
The three rear columns were then erected and the perimeter arches installed.
The length of these curved pipes meant site welding was required to achieve an
uninterrupted arc and these were achieved with an internal collar pipe.
Bespoke tower structures were designed and fabricated by STS Engineering with
an adjustable top fixing to provide the flexibility required for temporary support
to the various orientations of the prefabricated node assemblies in their final
position while the adjoining infill members were welded between them and the
adjacent modules. This propping ‘swept’ across the structure as the gridshell
infill completed from the building corner to the outer ground node gained its full
structural integrity.
CONCLUSION
The conception, design and fabrication of this structure took place while a
debate within structural engineering around ‘Just because we can do it doesn’t
mean we should’ has become increasingly vocal.
Why should contemporary capabilities of advanced analysis, geometry
generation and automated fabrication be concentrated on ‘solving problems
that didn’t need to be solved’ on structures and geometries that are perhaps
unnecessarily complex?
The authors believe that in this case such complications and ‘gymnastics’ were
justified due to the nature of the structure as a sculptural centrepiece to the
new city and a catalyst around which the life of its inhabitants will take shape
as they hopefully enjoy the space for everything from simple lunchtime shade to
large gatherings at evening events.
Its form and construction take many cues and influence from the forces acting
on it and these are articulated in both logical structural solutions such as the
large-scale ripple/corrugation of the gridshell surface and the more ‘poetic’
expression of structural actions such as the leaning form of the rear columns.
Both are considered to equally contribute to its success.