Civil Engineering | August 2011 August 2011 Vol 19 No 7 ENVIRONMENTAL ENGINEERING ENVIRONMENTAL ENGINEERING • The Fracking Debate • The Fracking Debate • Disaster Risk Management • Disaster Risk Management • Fisantekraal Wastewater Treatment Plant • Fisantekraal Wastewater Treatment Plant Western and Southern Cape Projects Western and Southern Cape Projects SAICE AND PROFESSIONAL NEWS SAICE AND PROFESSIONAL NEWS • CESMM3 for Southern Africa • CESMM3 for Southern Africa • Photo Competition Winners • Photo Competition Winners
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Western and Southern Cape ProjectsWestern and Southern Cape ProjectsSAICE AND PROFESSIONAL NEWSSAICE AND PROFESSIONAL NEWS• CESMM3 for Southern Africa• CESMM3 for Southern Africa• Photo Competition Winners• Photo Competition Winners
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Civil Engineering | August 2011 1
August 2011 Vol 19 No 7
ON THE COVERThe AfriSam Slagment Operation in
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bridges, roads and water-retaining structures
Civil Engineering | August 2011 1
August 2011 Vol 19 No 7
ENVIRONMENTAL ENGINEERING
SAICE AND PROFESSIONAL NEWS
FROM THE CEO’S DESKRight down the middle 3
OPINIONIs it us, or is it climate change? 6
ENVIRONMENTAL ENGINEERINGOn fracking in the Karoo, open forums and the power of public opinion… 9
The importance of independent construction quality assurance (CQA) services for the installation of geosynthetic lining systems 12
Disaster Risk Management – planning for resilient and sustainable societies 16
S&P JV on track with Cape Town’s Fisantekraal Wastewater Treatment Plant 20
Quantitative Analysis of EIA for Environmental Engineers 25
Public transport and the environment – the way forward 30
WESTERN CAPEImplementation of school construction in the Western Cape 35
Upgrade of rental stock in the City of Cape Town 40
SOUTHERN CAPELight-gauge steel frame development in the Southern Cape 43
MARKET CONTRIBUTIONPost-tensioning: the right solution 47
OMB Waste Logistics takes waste underground 50
Amanzimtoti rehabilitation of dune slopes using Green Terramesh 52
Mezzanines in minutes 54
IN BRIEF 56 World’s fi rst commercial wave power plant
inaugurated Veolia to upgrade Bellville Wastewater Works Corobrik pavers beautify PE inner city
Sika stands up for sustainability and health & safety Mapei helps to reinforce concrete columns
Precast concrete standards and the CPA Lady civil engineer wins 2011 L’Oréal-UNESCO Fellowship
SAICE AND PROFESSIONAL NEWSA new standard system of measurement for civil engineering quantities in southern Africa (CESMM3) 62
Winners of the AfriSam-SAICE Electronic Photo Competition 2011 64
The United Nations Conference on Sustainable Development for 2012 – Regional Workshop for Africa 66
Strengthening ties with our Nigerian colleagues 67
SAICE UCT Student Chapter – visit to the Berg River Dam 68
Obituary – Professor Richard Loewenthal (or Richard the Lionheart!) 70
Diarise This 72
AfriSam wins M&G “Greening the Future” award 4 AfriSam had committed itself to reducing its burden on the environment long before it became fashionable to do so
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Disaster Risk Management – planning for resilient and sustainable societiesINTRODUCTIONIt is generally accepted that disasters are having an increasing
impact on our lives, property, environment, infrastructure, and
economic and social activities. Globally, severe weather and
other natural phenomena, as well as human activities, are ex-
acting a heavy toll on us and the environment we depend on.
The results of disasters are human suffering, and damage
to the resources and infrastructure on which humans rely for
survival and quality of life. In the aftermath of a disaster, it is
critical to rapidly determine the exact nature of the impacts
and what will be required to restore the situation, or prefer-
ably to improve the situation by reducing vulnerability to
future impacts.
It is even more important to intervene pro-actively, before
disasters occur, to infl uence the process by which disaster and
operational risks develop, due to increasing vulnerability, re-
sulting in decreasing coping capacity.
DISASTER RISK MANAGEMENT – AN OVERVIEWAs defi ned by the South African Disaster Management Act
(Notice 654 of 2005), Disaster Risk is defi ned as the possibility, or
chance, of harmful consequence, or expected loss (of lives, people
injured, property, livelihoods, economic activity disrupted or en-
vironment damaged) resulting from interactions between natural
and human-induced hazards and vulnerable conditions. It is im-
portant to note that not all disasters happen with a sudden onset,
such as earthquakes or tsunamis. It is often the slow onset disas-
ters (e.g. environmental degradation, drought, changes in fl ood
prone areas / fl ood lines) that pose the higher risk if not identifi ed
and planned for in the Disaster Risk Management (DRM) process.
Although generally perceived as such, DRM is not only
reactive (the so-called response paradigm). Th e South African
Disaster Management Act (Act 57 of 2002) defi nes DRM as a
Prevention &
Mitigation strand
Preparedness
strand Relief & Response
strand
CRISIS
Recovery &
Rehabilitation strand
Prevention &
Mitigation strand
Time
1
1 The Disaster Risk Management continuum
2 The relationship between disasters (risk) and development
Civil Engineering | August 2011 17
“continuous and integrated multi-sectoral, multi-disciplinary
process of planning and implementation of measures aimed at:
(a) preventing or reducing the risk of disasters
(b) mitigating the severity or consequences of disasters
(c) emergency preparedness
(d) a rapid and eff ective response to disaster, and
(e) post-disaster recovery and rehabilitation.”
Figure 1 illustrates this life cycle of Disaster Risk Management –
the DRM continuum – illustrating a strong paradigm shift from
response towards risk reduction, shown as a continuous process
(the green strand), even during an event.
Internationally, governments have committed themselves to
taking action against disaster risk, and have adopted a guideline to
reduce vulnerabilities to hazards. Th is guideline is known as the
Hyogo Framework for Action, as defi ned by the United Nations
International Strategy for Disaster Reaction (UNISDR 2004).
Th e fi rst step for action is to make risk reduction a priority with
a strong institutional basis for implementation. In South Africa,
DRM is now regarded as ‘everybody’s business’, emphasising the
responsibilities of all role-players, and is especially not limited to
those historically associated with DRM. Th e Act (Act 57 of 2002)
also recognises that disasters know no boundaries and that plans
and strategies should be fi nalised in conjunction with neigh-
bouring municipalities and higher/lower spheres of government to
curb, where practical, the onslaught of disaster risk.
DISASTER RISK AND INTEGRATED PLANNINGTh e Act (Act 57 of 2002) requires that the disaster management
plan forms an integral part of the Integrated Development
Planning (IDP) process. Th is inter-relationship is also refl ected
in Section 26 of the Municipal Systems Act (Act 32 of 2002).
Th e National Spatial Development Perspective has broad-
ened the functionality of the IDP. It focuses on development
planning within a spatial extent, not a managerial entity, ir-
respective of the sphere of government responsible for certain
functions. Th is new approach gave rise to the so-called second
generation IDP, where integrated development planning is
performed through the implementation of a systematic process,
targeting distinct deliverables portrayed in the IDP to be ad-
dressed by councils for implementation (Louw 2007). It is
within this planning context that disaster risk must be identi-
fi ed, quantifi ed, planned for and implemented.
A FOCUS ON RISK REDUCTIONRisk reduction initiatives are essential as they form the fi rst
‘real’ barrier that, if nothing else, acts as a buff er by lowering the
vulnerability of the area impacted. Furthermore, reduction is
pre-emptive and is based on the perceived ‘anticipated’ risk sup-
plemented by historical data.
A disaster risk assessment is the fi rst step towards risk reduc-
tion. Disaster risk assessments, supported by eff ective moni-
toring, are essential for:
■ eff ective risk management planning
■ sustainable development planning
■ identifying potential threats that can undermine a develop-
ment’s success and sustainability, making it possible to incor-
porate risk reduction measures into project design prior to
implementation
■ identifying high risk periods and conditions, and
■ activating response and preparedness actions.
Relevant national organs of state must execute systematic dis-
aster risk assessments in the following instances:
■ prior to the implementation of any risk reduction, prepared-
ness or response programme
■ as an integral part of the planning phase for large-scale
housing, infrastructure or commercial/industrial develop-
ments of national signifi cance
■ as an integral component of the planning phase for nationally
signifi cant initiatives that aff ect the natural environment, and
2
Linking Disasters and Development: Some requirements are undefi ned
Positive developmental outcome
Negative developmental outcome
Disaster
ImpactDevelopment
Intervention
Disasterscreate
developmentopportunities
Disastersdestroy
development
Developmentreducesdisaster risk
Developmentincreasesdisaster risk
18 Civil Engineering | August 2011
■ when social, economic, infrastructural, environmental, cli-
matic or other indicators suggest changing patterns of risk.
Risk assessments must be undertaken to ensure that develop-
ment initiatives maximise their vulnerability reduction out-
comes. Th e relationship between development and Disaster
(Risk) is illustrated in Figure 2.
Th eoretically, the measures that can be considered for re-
ducing the risk of an area are fi ve-fold, taken from Botha and
Louw (2004) and summarised in Louw (2007):
1. Physical planning measures
Physical planning measures include the location of public
sector facilities that can reduce the vulnerability of an area,
such as schools, hospitals, major infrastructural elements
like wastewater treatment works and power transformers.
However, the consideration of disaster risks in spatial plan-
ning is extremely important. The development of residential
areas and the supporting infrastructure should always aim to
reduce risk.
2. Engineering/construction measures
Two types of engineering measures are possible. Th e fi rst option
results in stronger individual structures which are more resistant
to hazards, while the second option creates structures to protect
and alleviate against hazards, e.g. dykes, levees and dams.
3. Economic measures
Risk reduction measures that increase the capacity of a
community to cope with future losses create resilience in
dealing with losses and recovering from it. Examples include
incentive grants, tax rebates and economic diversification.
Economic development should be one of the main focuses of
regional planning.
4. Management and institutional measures
Institutional measures are very important and a longer term
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Quantitative Analysis of EIA for Environmental EngineersBACKGROUNDMany environmental impact assessment
(EIA) reports are lacking in science and
technology, in that they contain more de-
scription than scientifi c calculation. EIA
reports, which are vital tools for decision-
makers, involve specialised studies in spe-
cialised fi elds, many of which are based
on environmental engineering.
According to Brockman (2009), “Th e
main business of engineering is to apply
technology in concert with natural phe-
nomena to develop these things that we
need or want. Whereas the natural sci-
ences traditionally seek to discover how
things are, engineering focuses on the
question, ‘What form should we give to
this thing so that it will eff ectively serve
its purpose?’
“Most engineering problems are open-
ended, in that they don’t have a single
solution. Engineering approaches are
based on:
■ how to represent a design problem
■ how to make assumptions
■ how to generate possible ideas for designs
■ how to eff ectively conduct a search for
a solution
■ how to plan and schedule activities
■ how to make effi cient use of resources
■ how to organise the components and
activities of a team design project.”
Based on the above-mentioned approaches,
EIAs prepared by environmental engineers
are supported by calculations. Th is is the
main diff erence between EIAs written by
environmental engineers and EIAs written
by environmental scientists.
Nowadays most project owners/
managers are willing to cooperate with
EIA specialists from the planning stage to
avoid EIA-recommended alterations at a
later stage.
THE ENVIRONMENTAL IMPACT ASSESSMENTAn EIA report consists of:
■ Baseline data (existing environment
such as air, water, noise, community,
infrastructure)
■ Project data
■ Impact prediction, i.e. above-mentioned
two items combined
■ Mitigation measures, and
■ Monitoring programme.
Firstly, a project plan indicating the loca-
tion of the project site and surrounding
areas is given to the EIA specialist. It is
the responsibility of the EIA specialist to
then check the existing main drainage
system, and the drainage system of the
proposed project, as well as to estimate
the increased future stormwater runoff .
The Rational method is used to
estimate the quantity of runoff in the
project area:
Q = CIA
where
Q is the maximum fl ow
C is the coeffi cient of runoff areas
I is the average rainfall intensity, and
A is the drainage area.
Th en the sizes of the drains are
checked to determine whether they can ac-
commodate increased fl ow or not. For this
step: read the site map, and fi nd out the
size of the main drain and its direction.
26 Civil Engineering | August 2011
Water quality monitoring stations
Ambient air quality monitoring stations
Ambient noise level monitoring stations
Project Site
Project location and surrounding areas showing the following:
1
Civil Engineering | August 2011 27
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Industries:
uniformity, and standardisation between
schools. While layout design is approved
by the WCED at concept stage, drawings
and designs are submitted for approval to
DTPW as the ultimate custodian of the
facilities on behalf of the WCED. Local
authorities are also provided with courtesy
drawings for scrutiny and comment.
Along the way, some peculiarities
have been encountered relating to zoning,
sub-division or ownership of existing edu-
cational facilities. Th ese matters are dealt
with between the PIU, WCED and DTPW
property on a case-by-case basis.
All permanent construction to date
has been of a conventional nature (brick
and mortar), although the WCED has
expressed interest in investigating appro-
priate certifi ed/standardised alternative
construction technologies to expedite
delivery and/or reduce costs in future.
At a contractual level, the PIU imple-
ments similar contractual requirements in
terms of utilisation of local labour as are
required on other provincial projects. Th e
involvement of local communities is usually
facilitated through the School Governing
Bodies who identify appropriate CLOs for
the projects. As with most projects, those
projects which have the buy-in of the local
community from the beginning inevitably
have proven to be the most successful.
Financial Expenditure
Financial performance is always a critical
Key Performance Indicator. Th e PIU as-
sisted the WCED in achieving, for the fi rst
time, a 100% spend on their budget for the
2010/2011 fi nancial year. Moreover, only a
few months into the current fi nancial year,
and everything already appears on track
for the WCED to match their achievement
with an even larger budget this year.
CONCLUSIONTh e need within both the Western Cape,
and indeed the country as a whole, for
delivery of educational infrastructure is
immense. Th ere are tremendous pres-
sures on thinly stretched resources to
deliver, expand and maintain educational
infrastructure. Mechanisms such as the
WCED PIU off er a viable alternative or
additional delivery mechanism to assist in
expediting infrastructure delivery.
PROJECT TEAM
Client
Western Cape Education Department (WCED)
Programme Management Unit
Programme and Project Managers Aurecon SA (Pty) Ltd
Architectural Technical Advisor EHH Architects
Quantity Surveying Technical Advisor De Leeuw Group
Engineering Technical Advisor Aurecon SA (Pty) Ltd
Project Teams
Professional Teams (all disciplines) Numerous Professional Service Providers
Contractors Numerous Contractors
40 Civil Engineering | August 2011
AIMS AND OBJECTIVES OF THE PROJECTTh e project aims, fi rstly, to provide community upliftment and
act as a catalyst in presenting new development opportunities
for historically downtrodden communities. Secondly, the project
aims to ensure the upgrade of rental stock within budget and
on time. Th e project is a government-funded project, hence the
focus is on ensuring that the available budget is utilised in the
most advantageous manner for residents, as well as for the City,
who has to maintain these assets.
OVERVIEW OF THE UPGRADETh e upgrade includes general renovations to buildings, roofs,
electrical and plumbing systems, as well as the installation of
new ceilings, fl oor coverings, cupboards and geysers, fencing,
refuse management, area lighting, greening of areas and recrea-
tional facilities.
Th e process of rolling this out requires precision planning. A
temporary village has been established for the tenants to move
to whilst upgrading is in process. A block takes fi ve weeks to
complete, after which time the residents would be assisted to
move back to their upgraded units so that the next block could
be vacated for the builders to transform. Th e location of the tem-
porary accommodation is in close proximity to the rental units,
minimising disruption to the tenants’ daily lives. By arranging
new refuse collection points, cleaning of units between moves,
installing fi re hydrants, etc, Aurecon ensured that the village is
kept in a good, clean condition, without compromising the safety
of the residents, and ensuring a safe environment at all times.
Community participation is also a key element in the success
of the project. Comprehensive engagement of communities began
with the establishment of Project Steering Committees. Various
community representatives, including the local Ward Councillor,
serve on these committees and attend the monthly meetings.
PROBLEMS ENCOUNTERED AND INNOVATIONSProblem 1
Initially there was a notion that the tenants should stay in the
buildings during the renovations. However, it was acknow-
ledged that, due to the magnitude of work required to upgrade
these units, their staying in the units would not only slow down
progress to unacceptable levels, but tenants would be at great risk
of getting injured.
Innovation 1
All options for relocation were considered to ensure that costs
were kept within budget, and to ensure minimal disruption to
the residents’ daily lives. Tenants were fully consulted in order
to identify the most suitable solution. Aurecon designed a tem-
porary village which met the stringent standards set by the City
– converted containers for residents to stay in whilst their fl ats
are being refurbished.
Th e 12-metre converted containers have windows and doors,
insulation, partitions, a bathroom, free electricity, and free hot
and cold water. Aspects such as garbage collection and delivery
of mail were also considered to ensure a comfortable stay.
Communal dish antennas were even provided for those who have
decoders. Th is arrangement is cutting down by half the con-
struction time for each block.
Th e temporary village will be dismantled at the end of the
project to prevent the formation of an informal settlement.
Problem 2
Many buildings have families residing in informal structures at
the back of the buildings (back-yarders). Th ese are often attached
INTRODUCTIONIn 2007 the light steel frame system was
introduced in the Southern Cape under
the guidance of the Southern African
Institute of Steel Construction (SAISC).
Shortly thereafter two manufacturing
plants opened their doors, one in George
and the other in Mossel Bay.
Th e system consists of automated roll-
formers with cutting, punching, bending
and dimple-forming modules. Th e roll-
former machine is controlled by computer
and a specifi cally developed CAD pro-
gram (Framecad) to enable it to produce
ready-for-use sections from 0,75 – 1,0 mm
pre-galvanised plates. Th e sections are
then screwed together to form various
components (such as panels, trusses or
girder trusses) that can be joined together
to build the frame of a house, for example.
SASFA CODE OF PRACTICETh e SASFA (Southern African Light Steel
Frame Building Association) Code for
Low-rise Light Steel Frame Buildings was
published in October 2007. Th is code
provides the rules and requirements for
the design, fabrication and construction
of buildings with light-gauge steel frames,
primarily houses and other buildings of
limited size. Supervision of an engineer
is recommended, and is compulsory for
buildings falling outside the scope of the
code. Th e code has since been superseded
by SANS 517:2009.
HOUSING SYSTEM OR STRUCTURAL MATERIAL?From May to August 2008 experience was
gained on this system through a dozen
housing projects. Lighter foundations
were designed to suit the reduced weight
and higher fl exibility of the steel. Various
beam and connection options were also
analysed and discussed.
After the initial phase, two project
proposals exposed the need to move
beyond the scope of the code. Th e fi rst
was the proposed Hornlee Village in
Knysna, where the developer was plan-
ning a number of four-storey blocks of
fl ats, comprising eight units each, with
an average unit size of 60 m2. A three-di-
mensional steel frame made up of I-beams
was proposed to serve as skeleton for the
light-gauge steel.
Th e second proposal came from Titan
Aviation in George, who required an exten-
sion to their 23 m span helicopter hangar.
Th e architect requested a comparison
between a truss made from angle iron
and one made from light-gauge steel. Th e
light-gauge truss showed considerable
promise in both cases.
Although the two proposals did not
progress to construction, the experience
gained was used in later projects, such
as the following three projects that were
completed successfully.
House Blue Myrtle, Vleesbaai
In October 2008 Ictus Studio Architects
headed the design and construction of
a double-storey luxury sea-facing house
with the intent to utilise light-gauge steel
for the structure.
A raft foundation, made up of two
parts that hinge around the internal re-
taining wall, was designed to make use of
the greater ductility of steel compared to
masonry. Square hollow-section steel was
used for the external columns supporting
both the balcony and the overhanging
roof. Each column had a diff erent orien-
tation to improve the aesthetics of the
façade. Two square hollow sections were
also used as internal columns to support
the fl oor and roof over the wide opening.
Th e wall panels were planned to ac-
commodate the curved roof, and in the
main bedroom a curved wall was built.
All services were accommodated within
the walls.
Th e roof and fi rst fl oor joists were
slotted into the wall panels and sides,
hanging from the bearer trusses. Th e
Light-gauge steel frame development in the Southern Cape
44 Civil Engineering | August 2011
connectors were made from hand-
machined plates, while the ring beam on
the outer ring of the balcony consisted
of two standard C-sections forming an
enlarged box section.
Th e house was completed in 2009 and
valuable experience was gained in the use
of light-gauge steel together with standard
square hollow sections. Th is project proved
that it is possible to construct aesthetic
buildings with light-gauge steel. Th e project
was shortlisted for the 2010 SAISC awards.
Mezzanine fl oor for Bali Trading, Riversdale
Th e client required a mezzanine fl oor
as a furniture showroom. Design and
construction had to take place within two
months and with minimum disruption to
the existing store on the ground level. Th e
U-shaped fl oor area of 290 m2 was there-
fore constructed in two stages, allowing
the shop to continue doing business during
construction. A series of three parallel
trusses and one cross-bearer truss allowed
the use of 5 m light-girder trusses spaced
at 500 mm centres to be used on top of
the bearer trusses. Each bearer truss was
made up of two lattice girders side by side
and screwed together with plate stiff eners
at maximum hogging and sagging mo-
ments. Th e continuous-bearer trusses were
supported at 5 m centres, and at the end
by angle iron brackets to the steel portal
frame. Th e seven supporting columns
consisted of two 400 mm deep lattice
trusses each. No strengthening of the fl oor
was required as it had been designed for
110 mm masonry walls.
Th is simple arrangement made for
fast and easy construction. Th e total
structural weight was about 2 600 kg or
8,85 kg/m2 for a 2 kN/m2 load. Th e project
was completed within the four-week con-
struction period, illustrating that the ma-
terial can be used effi ciently in suspended
fl ooring applications.
1
4 5
1 House Blue Myrtle: frame
exposed during construction
2 House Blue Myrtle: front view
of house after completion
3 House Blue Myrtle: trusses
as feature in living room
4 Bali Trading mezzanine fl oor: lattice
girder truss on joist, and stiff eners exposed
5 Bali Trading mezzanine fl oor: the fl oor
two weeks later as part of the showroom
6 Steyns-Holzfaller shop and fl ats: hot-
rolled skeleton inner frame and a light-
gauge outer frame before cladding
Civil Engineering | August 2011 45
Steyns-Holzfaller shop and fl ats, Danabaai
In August 2010 planning and design
commenced for the construction of a
two-storey 760 m2 building comprising a
hardware store on the ground fl oor and
four apartments on the fi rst fl oor.
Th e use of the ‘solid wall’ system was
requested to improve wall insulation and
reduce noise. Th is system consists mainly
of vertical sections clad both sides with
fi bre cement boards. Horizontal steel sec-
tions are fi xed and holes are made at stra-
tegic positions. Hereafter a light-weight
concrete mix with polystyrene bubbles
is pumped into the cavity. Th e solid wall
system was also used upstairs as fi rewalls.
Th e typical wall will induce a load of only
1,2 kN/m onto the slab.
Th e core structure consisted of three
portal-type frames with square tubing
columns and horizontal I-beams. A com-
posite fl oor was developed, drawing on
factory trials and experience gained from
previous projects.
A concrete slab was chosen to re-
duce fire risk and noise transmission, as
well as to reduce the weight, and hence
the cost. The composite slab was made
up of light-gauge steel joists of 300 mm
deep, with a 58 mm concrete slab cast
on permanent plywood shutters. The
shear connectors consisted of two types
of bent plate sourced from machine
offcuts that would also act as spacers
for the steel mesh. Hogging reinforcing
steel was placed in the concrete in both
6
2 3
46 Civil Engineering | August 2011
directions to make the composite slab
continuous in both directions.
Th e project was completed nearly on
schedule. Delays were caused by subcon-
tractors not delivering components to speci-
fi cations. Although the hogging steel details
were changed, unwanted web sagging in the
joist trusses occurred during casting. Th is
was rectifi ed by propping the trusses until
the concrete had cured and composite ac-
tion developed suffi cient strength.
SUMMARYTh e use of light-gauge steel was initially
associated with the construction of
houses. Due to a combination of eco-
nomic need, constant requests and a
willing team, the scope of usage has been
broadened. Th e three projects discussed
above prove that light-gauge steel can be
used successfully outside the scope of the
design code and the suppliers’ CAD pro-
grams. Th e notion that light-gauge steel
is a housing system only has been chal-
lenged. Light-gauge steel should rather be
seen as a variation of cold-formed steel
design, using screws for the connections.
Continued development will improve
both the scope and the effi ciency of con-
struction with light-gauge steel. Some
possible improvements are:
■ In view of the limits of the CAD opera-
tors, the practice of making workshop
drawings should be enforced.
■ An erection code similar to SANS 10243
(timber) may assist the erectors to
prevent damaging panels, speed up con-
struction, and increase safety.
■ Th e support from the SAISC was
encouraging, but more focus could be
placed on project management and the
important role of the architect in areas
where formal contracts are not used.
■ Investors in machinery and building
equipment could be approached to de-
velop more productive methods.
Th e introduction of light-gauge steel to
the Southern Cape raised considerable
interest, with a number of entrepreneurs
becoming involved. Many lessons were
learnt, and mistakes were made. Th is is all
part of pushing the boundary.
7
8
9
7 Steyns-Holzfaller shop and fl ats:
composite slab made up of concrete
and light-gauge steel joists
8 Steyns-Holzfaller shop and fl ats: pumping
of light-weight concrete into wall panels
9 Steyns-Holzfaller shop and fl ats: front view
of building during construction of second fl oor
Civil Engineering | August 2011 47
THE 14-HOUR POUROn Monday 11 October 2010, possibly
the largest ever (area-based) single-pour
post-tensioned (PT) slab on ground pave-
ment was completed at Toll-Intermodal’s
container storage facility in Laverton,
Victoria, Australia. At 5 824 m2 it incor-
porated over 50 tonnes of post-tensioning
cable and required some 1 590 m3 45 MPa
concrete. Th e 260 mm thick slab is the
largest single pour area of post-tensioned
concrete ever constructed in Australia.
Commencing at 3:30, the pour took
approximately 14 hours to complete, using
three concrete boom pumps, two laser-con-
trolled screed machines, three twin-head
ride-on trowelling machines and coordi-
nating over 260 concrete truck deliveries
from two dedicated concrete batch plants.
Th is pour was the fi nal slab section
in a two-year pavement replacement pro-
gramme undertaken at the site to repair
approximately 20 000 m2 of failed and
badly cracked concrete pavement. For this
project, the structures team from Hyder
Consulting’s Melbourne offi ce prepared the
design and documentation and provided
construction planning, advice and super-
vision services to Toll-Intermodal while
Structural Systems were contracted for the
post-tensioning site installation works.
Th e pavements were designed to sup-
port 35 tonne container boxes stacked up
to three high, and they can accommodate
unlimited repetitions of 110 tonne axle
load ‘reachstacker’ forklift vehicles. A
260 mm thick post-tensioned concrete
pavement slab was adopted, using a range
of pour sizes to suit the site conditions
and areas of damaged slabs that needed to
be replaced.
Reconstruction work included demoli-
tion and removal of the existing damaged
and/or settled concrete, reworking of the
underlying subgrade (generally reactive
basaltic clays), provision of a 150 mm
thick cement-stabilised sub-base, the
addition of subsurface drainage, and pave-
ment reconstruction using high-capacity
post-tensioned concrete.
A feature of completed post-tensioned
slabs is the large joint-free areas produced.
Th is was a particular attraction for this
site, given the problems experienced with
maintaining and sealing the many closely
spaced joints in the original pavements.
THE PURPOSE OF POST-TENSIONING IN CONCRETE GROUND PAVEMENTSPost-tensioning in concrete pavements
has two functions – fi rstly, to counter-
act shrinkage cracking from about
18 – 24 hours onwards, and secondly, to
pre-compress the concrete to counteract
cracking due to ongoing shrinkage,
fl exural tensile stresses from service loads
and temperature gradient in concrete.
Th e post-tensioning system used is a
bonded fl at-slab system that follows the
following basic methodology:
1. Slabs are cast with high-tensile pre-
stressing strands running through the
slab from edge to edge, at regular spac-
ings, inside galvanised fl at oval ducts.
2. Tendons are unprofi led (fl at) in one
layer, with equal or close-to-equal
quantities in orthogonal directions.
3. Tendons are anchored at the slab edges
and stressed after concrete placement,
thereby placing a permanent two-way
compression force on the slab.
4. Th is force is then locked in by grouting
the ducts with a high-strength grout
which also acts as corrosion protection.
5. Post-tensioning couplers are available
for up to fi ve 12,7 mm strands, or fi ve
15,2 mm strands, and are valuable for
construction joints.
Post-tensioned slabs on grade are used
in industrial structures where the main
1
1 The crew from Structural Systems installing
bonded post-tensioning system for the
5 842 m2 post-tensioned ground slab at
the Toll-Intermodal container storage
facility in Laverton, Victoria, Australia
M A R K E T C O N T R I B U T I O N
Post-tensioning: the right solution
48 Civil Engineering | August 2011
objective is to eliminate joints that are
the major weakness in ground slabs.
The post-tensioning system allows a
significant reduction in the number
of joints, while keeping the structure
within allowable tensile stresses, re-
sulting in lower maintenance costs over
the design life of the slab.
Concrete has limited capacity to
resist tensile stresses. For conventional
reinforced concrete slabs, or slabs with
steel fi bre reinforcement, the thickness
and primary reinforcement are increased
so that the stresses do not exceed the
concrete tensile strength. Post-tensioning
allows balancing of the tensile stresses
in the concrete, leading to thinner slabs
without the need to signifi cantly increase
the amount of reinforcement.
Th e major advantages of using a
post-tensioned slab on grade solution
compared to other ground slab systems
are as follows:
■ Eff ective load support – it is a properly
engineered fl oor designed for any load
system.
■ Active crack control – post-tensioned
slabs reduce the risk of cracking far
more eff ectively than any other method,
due to the active compression force
exerted on the slab.
■ Fewer or no joints – the use of a post-
tensioned slab on grade solution greatly
reduces the joints required in a fl oor,
with resulting reduced maintenance.
2
3
4
2 Post-tensioned ground slab of 5 824 m2
ready for concreting at the Toll-Intermodal site
3 Construction of a heavy-duty external
post-tensioned ground slab at Molineaux
Point in Botany, Australia – PT slab design
and site PT works by Structural Systems
4 Completed post-tensioned 28 000 m2
ground slab for Coca Cola’s Amatil Distribution
Centre in Sydney, Australia – PT slab design
and site PT works by Structural Systems
Civil Engineering | August 2011 49
Structural Systems (Africa) is a specialist engineering company providing Design, Materials, Equipment,on-site services and expertise throughoutSouthern Africa in the following fields:
1 and 2 The use of Corobrik Burgundy pavers has brought an authentic, rustic feel
to the Port Elizabeth city centre. Photo 1 shows the city centre with the City Hall in the
background, while photo 2 captures both the library (on the right) and the City Hall
1
2
“The upgrade taking place in PE has transformed the city centre to such
a degree that we understand NMBM has now decided to include neigh-
bouring streets that were not originally part of the project,” concludes Kidger.
INFO
Peter Kidger
Corobrik
031 560 3233
Hedwig Crooijmans-Allers
The Matrix Urban Design and Architects
041 582 1073
Bryan Wintermeyer
The Workplace Architects
041 582 4390
SIKA STANDS UP FOR SUSTAINABILITY
AND HEALTH & SAFETY
NOW IN ITS 101st year of supplying materials to the construction and
automobile industries, Sika also sets itself the highest standards of
environmental management by complying with ISO14001. Sika SA
Managing Director, Paul Adams, says, “Achieving ISO ratings neces-
sitates a continual improvement in management systems. In gaining
ISO 14001 Sika is demonstrating its total commitment to sustaina-
bility. We are continually striving to source new and environmentally-
friendly raw materials and are focusing on the elimination of harmful
solvents in production.”
Sika SA was the fi rst construction chemical company in South Africa
to achieve this in 2006, and is still the only construction chemical com-
pany to have this rating.
Adams claims it does not help to source a few products from third
parties and claim your company is green. He also advises end users and
specifi cers to visit manufacturing plants such as Sika to see that the company
is truly committed to sustainability. “Ask them about disposal procedures and
raw material sourcing. ISO 14001 helps us at Sika to commit to the ‘cradle to
the grave concept’. Many international companies are now looking to com-
panies that have the ISO 14001, as it gives them security in knowing that envi-
ronmental standards are being considered and adhered to by the supplier.”
Sika is now pleased to announce yet another achievement – the
Occupational Health and Safety Certifi cation (OHSAS 18001), awarded
in 2011. Sika is the fi rst construction chemicals company in South Africa
to be awarded this certifi cation.
OHSAS 18001 is an Occupation Health and Safety Assessment Series for
health and safety management systems. Intended to help organisations con-
trol occupational health and safety risks in the workplace, it was developed in
response to widespread demand for a recognised standard against which to
be certifi ed and assessed. Sika, in conjunction with OHSAS 18001, is fully com-
mitted to health and safety in the workplace, and the safety of the workforce.
Adams says, “As an OHSAS 18001 company, you have nowhere to hide.
All incidents are reported and recorded. Health & Safety offi cers have been
appointed who continually monitor H&S on Sika premises. No contractor
may perform duties on our premises until they have been fully inducted to
ensure all their equipment and staff comply with Sika standards. Our factory,
administration and distribution staff are continually updated regarding leg-
islation and new improvements at third-party training centres.”
OHSAS 18001 has been developed to be compatible with the
ISO 14001 (Environmental Management Systems) standards. The ISO 14001
enables the company to:
■ Identify and control the environmental impact of its activities, prod-
ucts and/or services.
■ Improve its environmental performance continually.
■ Implement a systematic approach to setting environmental objectives
and targets, and to demonstrate that they have been achieved.
Adams concludes , “As Sika is the oldest and largest construction chemical
company in the world, we cannot simply rely on being market leaders when
it comes to existing and new technology. The environment, and health and
safety need to be attended to seriously as well. Sika strives to ensure that the
full system approach, ‘Roof to Floor’, is sustainable.”
INFO
Paul Adams
Managing Director
Sika South Africa (Pty) Ltd
031 792 6500
MAPEI HELPS TO REINFORCE
CONCRETE COLUMNS
MAPEI SOUTH AFRICA, part of the global Mapei Group, with specialist
contractor Mndeni Structural Services, was contracted by Stefanutti
Stocks, to help with the repair of concrete columns in a multi-storey
parking garage for the University of Pretoria.
The columns were designed for a comprehensive strength of
30 MPa, but after construction they measured an approximate 25 MPa.
To accommodate this shortfall, the columns had to be strengthened.
1
1 Sika, the oldest and largest construction chemical company in the world
58 Civil Engineering | August 2011
Sika
Roof
Completely seamlessCold appliedElastomeric and durableRoot resistant waterproofing membraneEasy to repair if puncturedCan be applied in damp conditionsQuick and easy to applyIncreases thermal performance
Advanced waterproofing technology for Africa – Sikalastic MTC®
Civil Engineering | August 2011 59
Carbon fi bre wrapping was the preferred option, as it is strong but light-
weight, and MapeWrap C UNI-AX 600/40 met the project requirements.
Before the wrapping could be applied, the columns had to be thoroughly
prepared. First, laitance was removed with grinding and sandblasting to pro-
vide an open texture surface. In the next step, MapeWrap Primer 1 – an epoxy
primer specifi c to the MapeWrap system – was applied to promote adhesion.
All blowholes were then fi lled with Adesilex PG2, a two-component
epoxy resin-based product containing special hardeners that off er extended
workability and are ideal for structural strengthening and sealing large cracks.
MapeWrap C UNI-AX 600/40, a high-strength, uni-directional, con-
tinuous carbon fi bre fabric with a very high modulus of elasticity and
high tensile strength, was then layered tightly around the columns in
segments, with overlaps. To impregnate the MapeWrap, MapeWrap 31, a
medium-viscosity epoxy resin, was applied to the concrete.
In the next step, the MapeWrap C UNI-AX 600/40 was rolled on with a
steel roller to remove any trapped air bubbles, and blinded with silica sand.
After the epoxy had hardened, excess sand was brushed off and a skim-
ming mortar was applied to the columns. Planitop 200, a single-component
cementitious mortar with high bonding strength, was applied in the fi nal
step to smooth the surface, protect the wrapping and fi nish off the columns.
Free BIM software for project collaborationDownload Tekla BIMsight at www.teklabimsight.com
We love models. And we believe that once you download the new Tekla BIMsight, so will you. Combine models, check for clashes and enjoy seamless communication - Tekla BIMsight will change the way you manage your construction projects.
Cadex SA, Tekla’s Partner for Southern Africa [email protected] or www.CadexSA.com
64 Civil Engineering | August 2011
Winners of the AfriSam – SAICE
Electronic Photo Competition 2011
1
1 FIRST: Dawning of a new day
Photographer: K Marais
2 SECOND: Hospital Bend at night
Photographer: Bruce Sutherland
3 THIRD: Cape Town Stadium during the FIFA World Cup
Photographer: Bruce Sutherland
Civil Engineering | August 2011 65
For the first time in its history, SAICE’s ever popular photo
competition was presented in electronic format this year, drawing
126 high-resolution entries. The first round of voting was done
online by SAICE members (we received more than a thousand votes),
narrowing the entries down to a shortlist of finalists from which
the winning photographs were selected by a panel of judges. The
adjudication took place on Tuesday 21 June at the historic Liliesleaf
Farm in Rivonia, with AfriSam kindly sponsoring the event
2
3
66 Civil Engineering | August 2011
The United Nations Conference on Sustainable Development 2012 –
Regional Workshop for AfricaSAICE WAS INVITED by the
World Federation of Engineering
Organisations (WFEO) to attend the
Africa Regional Workshop, which
was held in Pretoria from 30 May –
1 June 2011. The event was organised
by the International Council for Science
(ICSU) (Regional Office for Africa)
and the United Nations Educational,
Scientific and Cultural Organisation
(UNESCO), Nairobi. Manglin Pillay,
CEO of SAICE, and Lorraine de Ronde,
SAICE International Liaison Officer,
attended the workshop.
Th e United Nations Conference on
Sustainable Development 2012, also
known as “Rio+20”, is scheduled for 4 –
6 June 2012 in Rio de Janeiro, Brazil, the
same city where the fi rst Earth Summit
was held in 1992. In preparation for the
event, fi ve regional workshops for Asia
Pacifi c, Latin America and the Caribbean,
Africa, the Arab Region and Europe
were organised to aff ord scientists and
engineers from the diff erent regions the
opportunity to prepare joint positions and
concerted input into the processes leading
to Rio+20. Delegates came from various
African countries and included natural
and social scientists, engineers, policy-
makers and government representatives,
major group representatives, research
organisations, educational institutions,
UNESCO and ICSU.
Th e objectives of Rio+20 include,
among others:
■ To secure renewed political commit-
ment for sustainable development.
■ To assess progress to date of the fi rst
summit (1992 Earth Summit).
■ To identify the remaining gaps that
inhibit progress.
■ To implement the outcomes of the major
summits on sustainable development.
■ To address new and emerging challenges.
Delegates at the recent Rio+20 Africa Regional
Workshop in Pretoria – from left:
Prof Alice Abreu (ICSU, Paris),
Manglin Pillay (CEO, SAICE),
Edith Madela-Mntla (ICSU Regional Offi ce for Africa),
Prof Joseph Massaquoi (UNESCO, Nairobi),
Prof Lidio Brito (UNESCO, Paris) and
Lorraine de Ronde (SAICE International Liaison Offi cer)