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.
(Reference
is made to Cordell's Building Cost Guide under the chapter "Building
Cost Indicators" which lists such group separately also)
In
most of these buildings the Kneebone & Beretta Group has
found that conventional reinforced concrete floor systems have
proven to be the most economical structural matrix. The basic
restraints of reinforced concrete slabs consist of limited spans
for flat plates and limited floor dimensions without joints.
Research by VSL Prestressing indicates that flat plates
with average spans around 7.0 metres are generally more economical
in reinforced concrete. In addition the Kneebone &
Beretta Group has found that in the case of one or two floors
only, builders prefer to remain with conventional type construction
such as reinforced concrete. To give some guidance to
the designers of such buildings we can make the following suggestions
for proposed floor systems.
Over carparking areas the column spacing should not exceed 3
carparking widths (assumed as 7.8 metres) and the width of a
driveway (assumed as 7.0 metres plus the column width) if flat
plate floors are proposed. The thickness of such floors depend
on the proposed use. For another parking floor, retail or office
floor these slabs should be at least 220mm thick with no drop
panels or 200mm thick with 150mm additional thickness in the
drop panels.
Example 1: Noosa Shopping Centre
Where
floors need to support brick walls slab thicknesses should be
increased by about 10% to limit deflections. See ground
floor slab for Strathfield Arcade. Note on this sample
where spans exceed 7.8 metres slab bands as beams have been
incorporated. It is also noted that such slabs are particularly
useful where steps for ramps or garden areas are required.
The columns lay-out must continue if another floor is to be
supported. Where columns are not continuous a transfer slab
or beams are required.
Example 2: Strathfield Shopping Arcade
For
general information about slab and drop panel thicknesses see
graphics attachment A
Attachment A: Multispan Flat Slabs
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.
