Architect and Builder November/December 2015 | Page 62

S

teel Awards 2015 has come and gone and, according
to Awards Convenor, the Southern African Institute of
Steel Construction’s (SAISC), Spencer Erling, the quality
of the entries easily matched the outstanding quality
of previous years. “We are going through very tough
times in the steel construction industry yet, in spite of this, we are
able to produce world-class work - an indication that the future is a
bright one,” he said.
Steel Awards 2015 was held simultaneously in Johannesburg,
Cape Town and Durban on 3 September. The sponsors were:

STEEL
AWARDS
2015
Main: AVENG Steel
Table Décor: Peddinghaus
Photo Competition: Cadex Systems SA
Tubular Category: The Association of Steel
Tube and Pipe Manufacturers
Light Steel Frame Category: Saint-Gobain
Metal cladding category: Global Roofing Solutions
Factory and warehouse category: B&T Steel
Partner Sponsors: ArcelorMittal SA, EVRAZ Highveld Steel
& Vanadium, Genrec Engineering, Macsteel and NJR Steel

OVERALL WINNER AND TUBULAR CATEGORY WINNER: SKA Africa Radio Antenna Positioner
The SKA Africa Radio Antenna Positioner was the Overall Winner
at Steel Awards 2015. It was also the winner of the of the Association
of Steel Tube and Pipe Manufacturers (ASTPM) Tubular category.
The judges said that this project “radiates excellence not only
in the use of structural steel but in every aspect of its structure
and purpose.”
Part of South Africa’s technical capability displayed in the bid
for the SKA was backed up by the design and build of the seven
dishes for the SKA Africa Telescope. The SKA Africa programme
is for 64 antenna positioners to be completed by late 2016, on a
site 90 kilometres from Carnarvon, Northern Cape, without mobile
phone contact and far from engineering resources.
Each receptor consists of three main components: the antenna
positioner, which is described as a steerable dish on a pedestal - the
judges thought this, in itself, was superb use of steelwork - a set of
radio receivers and the associated digitisers.
The judges noted that the enormous complexity of the geometry
for the antennae “must surely compete with last year’s overall
winner, the Malapa project, which was complex but was built with
the luxury of our normal two millimetre structural tolerances.”
The antennae positioner allows for a vertical (tilt) range of 15°
to 88° and an azimuth range of 360° to an accuracy of within 1.4
thousandths of a degree under optimal conditions and 7 thousandths
of a degree during normal operational conditions. ”That’s a degree
of accuracy that is hard to grasp for structural engineers given the
fact that we normally work to the nearest two millimetres,” the
judges noted.
The largely tubular antennae support structure was built with zero
tolerance targets. “The engineering, detailing, jig fabrication and
construction move these structures into a different league from your
run-of-the-mill tubular truss type project. The accuracy of dimensions
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after erection is critical to give the radio telescope maximum chance
of achieving its unimaginable expected accuracy,” the judges said.
Small tube connections use overlapping Tee connections. The
larger bores, with higher loads, where an eccentricity in the Zed
direction could lead to movements in the connection, have been
designed with cover splice plates to the Tee joints, thereby ensuring
no eccentricities occur.
This type of structure is the perfect application for the use of
circular hollow sections. Careful detailing enables the centre of
gravity lines of the elements to meet in a common centroid. In
some connections, there are as many as 11 framing members.
The pedestal fabrication is largely out of plate and the interface
between the pedestal and yokes of the support structure are line
bored. Pedestals are erected before the antennae framework. The
frame is offloaded and erected directly from truck to pedestals
“A scientific project of this nature, that taxes the skills of South
African engineers and scientists to rise above the challenges and
make it work, represents excellence in every way, but it is especially
a triumph in the use of steelwork and is truly deserving of being
the Overall Winner of Steel Awards 2015,” the judges concluded.
Client / Developer: SKA Africa
Main Contractor/ Project Manager: General
Dynamics SATCOM Technologies
Structural Engineer: General Dynamics SATCOM
Technologies, Vertex Antennas (Germany)
Steelwork Contractors: Tricom Structures
BUS structure: Tricom Structures (a subsidiary of Robor)
Pedestal: Efficient Engineering
Structural Steel Detailer/ Detailing Company:
Tricom Structures (a subsidiary of Robor)
Steel Awards