The Civil Engineering Contractor July 2018 | Page 24

TECHNOLOGY
Bridges only have a certain lifespan, which is dependent on the strength of the cement used.
elimination of structure supports.
This is a common method more for
large buildings than infrastructure
such as bridges. The process is
dependent on factors like the area
where the building is located, the
building material, the purpose of
the demolition, and the way that
debris is going to be disposed of.
• High-reach
demolition:
This method has a threshold
height of more than 20 meters.
It is usually formed by a base
machine (excavator, tank, engine,
counterweights), a demolition arm
consisting of three sections, or by
a telescopic boom and a primary
tool attached to the base machine
(crushers, shears, hammers).
• Ball and crane: One of the oldest
and most used methods for building
demolition, the ball and crane uses a
wrecking ball weighing up to 13 500
pounds to demolish concrete and
masonry structures. The ball and
crane, however, is not suited to
all demolition applications. This
form of demolition creates a great
deal of dust, vibrations, and noise.
• Selective demolition: Although
it is a labour-intensive process
and often difficult to achieve in a
timely and economical manner, this
process is very popular right now.
The main purpose of this method is
to recover the maximum amount of
primarily reusable and secondary
recyclable material in a safe and
cost-effective procedure.
24 - CEC July 2018
• H y d r o d e m o l i t i o n :
Hydrodemolition is in its infancy in
Africa, but major structural repairs
to the M1 North highway bridges
over Oxford and Federation
roads in Johannesburg were
recently completed with the help
of hydrodemolition technology.
Commissioned
by
WBHO
Construction, in partnership with
Sanral, the project involved the
complete rehabilitation of the
bridges in Rosebank, involving
major
structural
repairs.
Hydrodemolition can target the
specific demolition area with
relative precision, which supports
a cleaner demolition site. Shotcrete
can be used in almost any concrete
project, and typically results
in a significant savings of time
and money. Unlike conventional
demolition
methods
like
jackhammering, hydrodemolition
does not damage the rebar or
surrounding structures. However,
it can be expensive.
Some demolition engineers focus on
steel-only structures. Steel is easier
to control than concrete as the latter
often just disintegrates.
Stiff competition among
local companies
Jet Demolition and Wreckers
Dismantling Cape offer full, turnkey
demolition services to the industrial
sector. Oftentimes this means
undertaking demolition works in
operational plants, immediately
adjacent to live services, and requires
careful integration of demolition
services with operational requirements.
“Jet Demolition is the leading, the
largest, and the most technically
advanced demolition company in
Africa. Accordingly, we have developed
demolition tools and methods that are
tailored to the task at hand, most of
which are not commercially available
locally,” says Bester. “We advocate
the separation of man from risk and
try to take a mechanical approach
to demolition wherever possible. Our
personnel are highly incentivised and
motivated, leading to a high skill-
retention throughout all economic
cycles. This differs greatly from most
demolition contracting companies, as
we value the skill offered by our teams
— this skill and a stable working
environment are crucial to the safe
and successful completion of the most
complicated demolition projects.”
What could possibly
go wrong?
Demolition is fraught with challenges,
and the skill of managing these
challenges defines the strength of a
company. The biggest challenge by far
is the management of people. “It is
critical to ensure skilled personnel
who are trained, confident in their
abilities, and firmly entrenched in a
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