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CONSTRUCTION WORLD
NOVEMBER
2016
FORMWORK AND SCAFFOLDING –
ADVERTORIAL
>
Client:
Johannesburg Development Agency
Main contractor:
WBHO
Design Engineer:
Hatch
Form-and-falsework:
Form-Scaff
Location:
Katherine Street, Sandton
Project type:
Cable Stay Bridge
in place and carefully tensioned later this year. Until such time Form-
Scaff’s combination of Super-Beams and Kwik-Stage will form the basis
of the support for the bridge.
“We also manufactured special formwork to pour the towering
52 m high main pylon and ensure that the cable anchors can be care-
fully aligned with the anchors on the road-level bridge beam. Lobster-
back forms were also made for the casting of piers that support the
bridge as it touches down on either side.
“With limited headroom across the 24 m and 27 m wide portals
over the north and south carriageways, our heavy capacity Super-
Beams provide the only feasible answer with a low enough profile for
unimpeded traffic below, while being strong enough to support the
thousands of tons of construction materials above. Another advantage
is that the five separate beams, each comprising four connected Super-
Beams, could be preassembled offsite to save time and space on the
crowded construction site,” says Erasmus.
Precast solution
WBHO construction manager for the BRT Cable Stay Bridge, Nicol
van Rensburg, says the construction starts with the Super-Beams
supporting 19 pre-stressed precast concrete transverse beams spaced
at 3,5 m intervals across the bridge. These 8,55 m long by 400 mm wide
and 750 mm high concrete beams then provide support for 100 mm
thick pre-stressed concrete planks which are in turn placed across the
3,5 m gap between the transverse beams.
Casting of the main beams and slabs follows with the main beams
tying into the exposed rebar of the transverse beams. At the same time
the main pylon is constructed with formwork designed to reduce in
plan dimension from 6 m at the base to 1,5 m at the top of the pylon.
More than 1 300 tons of Form-Scaff
form-and-falsework is on site at the
Katherine Street Bridge where WBHO is
undertaking a technically challenging
project to construct Sandton’s latest
showpiece structure.
With a span of 120 m including two bus lanes and a pedes-
trian walkway, the ultra-impressive cable stay bridge will
form part of the City of Johannesburg’s new generation Rea
Vaya BRT route linking Alexandra to Sandton. Its span over
South Africa’s busiest highway will provide safer and faster access to
the central business district for thousands of commuters every day.
During the construction phase however, the spanning of the
highway without impeding workday rush hour traffic is the greatest
challenge of all requiring the assistance of the country’s top structural
support experts to design and building temporary structures to allow
construction to continue unimpeded.
Custom designed
Chris Erasmus, Form-Scaff technical director, explains that the entire
weight of the bridge needs to be supported from the time of the first
concrete being laid (early last year), until the massive cable stays are
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