Mechanical Technology January 2015

Mechanical Technology — January 2015

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Special report

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uch was the quality of the steel

structure at the Malapa fossil

excavation site, which was the

overall winner and winner of

the Association of Steel Tube and Pipe

Manufacturers of South Africa’s Tubular

category, that Steel Awards 2014 con-

venor, Spencer Erling was prompted to

say: “It is surely the first time since I

have been managing the Steel Awards

process – this year is number 13 – that

the overall winner has ticked so many

boxes as to why this project represents

excellence in the use of steel.”

In 2008, Professor Lee Berger of the

University of Witwatersrand was using

Google Earth to look for possible fossil

deposits in the Cradle of Humankind.

What caught his eye was a nearly

circular ring of trees, something that

indicates a possible cave entrance or

potential fossil deposit. The rest is

paleontological history.

The brief for the Malapa fossil ex-

cavation site was to build a removable

structure over the dig site to protect the

site and the exposed fossils from the

extremes of the weather and to allow for

as much ‘dig time’ as possible. It had

to also blend in with the ring of trees

and the rest of the bush on the hillside

The structure had to, in addition,

have a tourist-viewing platform, a

crawl hoisting structure to lift rocks

weighing up to one ton, and maximum

possible natural light had to be able to

penetrate into the covered area. The

access walkway to the viewing platform

had to be like ‘a blanket over a baby’

so as not hinder the movement of the

natural wildlife – hence no handrails

were permitted.

The final shape when viewed from

above is like a beetle with eight legs. But

how can a structure be designed when

one does not know where the founda-

tions will be? Enter Peter Fellows, the

engineer. It was decided that during

construction, once positions were cho-

sen, rods would be drilled into rocks

around the site, onto which base plates

would be welded. This required that the

eight support columns be adjustable to

suit the plate positions identified.

The roof was to be ‘rondavel-like’ in

shape but not necessarily round, from

which would hang the viewing platform

and hoisting structure.

The detailing and fabrication of a

tubular structure such as this require

special skills, which were provided by

teams from Spiral Engineering, one of

the few companies in South Africa with

the capacity to build such complicated

structures.

To accommodate the site location –

with a 7.5 km farm track access road

that runs through a riverbed – special

trucks with limited capacity were used

on the farm. After four unsuccessful

tries, a 30-ton all-terrain crane with

a long enough radius and capacity to

In this special report,

MechTech

summarises the steel construction project

winners from last year’s Steel Awards 2014, hosted by the Southern African

Institute of Steel Construction (SAISC).

Excellence in the use of steel

access the structure without damaging

the trees and the bush, reached the site.

The judges concluded that the deter-

mination of the whole team, the quality

of their work, the fact that when you

visit the site the roof is not visible from

more than a few metres away, and that

the construction team left the site virtu-

ally as they found it, made this project

“excellent in the use of steel” for every

possible reason.

Category winners

No. 1 Silo, part of the first phase in

the Silo precinct development of The

V&A Waterfront, won the Architectural

category. This 10-storey development

consists of an east and west wing built

on two levels of a mega-basement cov-

ering the whole site.

Structural steelwork was the solu-

tion to provide slender support to the

facades, walkways, bridges, lifts and

feature stairs, while economically

extending the cantilevers of the con-

ventional post-tensioned slabs framing

the atrium.

The roof of the atrium is positioned

above an open volume area spanning

17 metres. A composite steel and con-

crete Bondek slab was designed to serve

as the primary support and waterproof-

ing line to an accessible and functional

roof. Another critical design element of

the atrium was the feature staircase that

served the five office levels.

Heritage requirements regarding the

treatment, restoration and reinstate-

ment of the existing structures were of

the utmost importance and underpin-