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COMMERCIAL
BUILDINGS
The
major factors influencing the design of commercial buildings
are dictated by client's demands, constraints imposed by the
site, as well as location and planning controls. Such issues
are generally best resolved by an experienced architect. Once
the shape of a commercial building has been decided the designer
than has to select the most economical and effective structure.
Group
2 - Multi-storey Commercial Buildings 3 to 10
storeys high.
Also includes large span commercial buildings.
(Reference
is made to Cordell's Building Cost Guide under the chapter "Building
Cost Indicators" which lists such group separately also)
Value
engineering management processes maintain, that they have consistently
proven that posttensioned concrete floor systems were the most
cost-effective construction for these kind of buildings in Australia.
Factors taken into account were not only the basic material
costs but also the effects on the speed of construction, floor
to floor heights, formwork, foundation loadings and room for
services. There is always a cost premium for increased
spans but this premium can be kept to a minimum by selecting
post tensioned concrete. An additional benefit of post-tensioned
concrete floors is the opportunity to cater for special heavy
loads such as compactus units and/or industrial floor loads.
Two basic systems are commonly adopted:
a.
Post-tensioned flat. slab, with or without drop panels.
As an example Kneebone & Beretta Group can show you
a flat slab adopted for a manufacturing floor for Autocal
where a column lay-out of 7324 by 7750mm was adopted but
a floor load of 10kPa had to be accommodated.
For normal loadings slab thicknesses of 1/44 of the larger
column spacing can generally be accomodated with post-tensioned
flat plate slabs with drop panels
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Example 3: Manufacturing Premises Mt Kuring-Gai
For
normal loadings slab thicknesses of 1/44 of the larger column
spacing can generally be accommodated with post-tensioned flat
plate slabs with drop panels.
b.
Post-tensioned wide band beams with post tensioned slab.
For
slabs over carparking areas the designer can now space
the columns over 4 carparks or about I 1. 0 metres and
across a driveway and generous set back giving about IL
6 metre spacing. Slab thickness of 210mm for normal loading
and 250mm for compactus loads with 2400mm wide by 500mm
thick beams can accommodate the above column layout.
The
above column spacing also the designer great freedom in
laying-out office areas and the columns are generally
taken right through the whole building.
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Example 4: Office Building Lakemba
As a note of caution designers should be carful when
ending slab band beams right at the edge of outside columns.
Congestion of column steel, prestressing anchors and anti-bursting
reinforcement can often cause the engineer and builder great
headaches. Even a small slab extension past the outside columns
can greatly facilitate construction and thereby achieve better
economies.
For
general information about slab and wide beam thicknesses, see
graphics attachment B.
Attachment B: Wide
Beam Post Tensional Slab
In
any case when ever a designer of a commercial building needs
advice on the structural system for his building please contact
Kneebone & Beretta Group on info@kneeboneandberetta.com
and an engineer will get back for your assistance.
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