Civil Engineering Reference
In-Depth Information
The value of achieving good quality in design, the issues
associated with this and how the achieved quality can be
assessed are discussed in Box 5.3. Design Quality Indicators
(DQIs) assess design quality under the three main headings of
impact
,
build quality and functionality
(see also
Figure 5.7
).
DQIs address a wide range of issues that go well beyond con-
sideration of the functional structure of the building or con-
structed asset, with the critical success factors for achieving
design quality being described in Box 5.3.
More information about DQIs can be found through the
Construction Industry Council website at www.dqi.org.uk.
Other specialist tools have been developed for specific sectors;
these include the
Achieving Excellence Design Evaluation
Toolkit
(AEDET) for the UK National Health Service (NHS)
and the
Design Excellence Evaluation Process
(DEEP) for UK
Defence Estates.
Definition of the owner's basic requirements will enable the
performance characteristics for the structure to be specified.
These
performance requirements
, together with an assessment
of the environmental loads, will form the basis of the design
solution and should include:
Safety and serviceability requirements.
■
Service life and clarity upon what constitutes the end of service life.
■
Importance of continuity of function and flexibility to accommo-
■
date changes of use.
Management and maintenance requirements.
■
Acceptable
level
of
inspection,
maintenance,
repair
or
■
replacement.
Acceptable life-cycle or whole-life costs (capital and operating
■
costs).
Design restrictions.
■
5.6.2 Owner brief and performance expectations
The owner brief addresses the relevant needs and aims of the
construction project, resources to be provided by the owner,
the details of the project and any appropriate design require-
ments within which all subsequent briefing (when needed)
and designing can take place. This stage of the design pro-
cess should highlight the important issues for the owner (and
parties advising and assisting the owner in the preparation of
the brief) to address in order to enable an effective service
life design to be undertaken. It may be subdivided into two
parts; the owner's basic needs and the consequent performance
requirements, as described below.
Owners vary greatly in their understanding of how to formu-
late and express their needs and a key role of the designer/con-
sultant is helping the owner to understand and express these
needs in terms that can be translated into clear performance
requirements.
Owner's basic needs:
The owner should consider a number
of basic issues that can influence the design and the perform-
ance requirements for the facility (i.e. the proposed building or
asset that is to be constructed). These include:
Agreed sustainability credentials and targets for minimising envir-
■
onmental impact.
The issue of life-cycle or whole-life cost encapsulates an
understanding of how design decisions affect not only the ini-
tial construction costs, but the costs of operating the structure
throughout its life. It is expected to become an increasingly sig-
nificant influence in the design process, along with sustainabil-
ity considerations. However, as with service life design, there
is still much work to be done to translate ongoing research in
these areas into a usable system.
Most of what follows is concerned with durability related
aspects of service life design; however, other considerations
may apply in particular circumstances (e.g. fatigue, thermal
performance effects, etc.).
5.6.3 Environment aggressivity classification
The environment to which the structure will be exposed is a
key factor in designing for a given service life. Relevant fac-
tors include:
The general environment conditions of the area in which the struc-
■
ture is situated (macro-climate).
The specific location and orientation of the surface being con-
What type of facility is needed and where is it to be located.
■
■
The planned function(s) of the facility and its component parts.
■
sidered and its exposure to prevailing winds, rainfall, etc. (meso-
climate).
Localised conditions (micro-climate) such as surface ponding, expos-
The performance requirements for the facility and its component
■
parts.
Any desired sustainability credentials.
■
■
ure to surface run-off and spray, aggressive agents, regular wetting,
condensation, etc. These aspects include those arising as a conse-
quence of the interaction between the structure and the environment
(e.g. cladding to keep the structure dry or ponding due to poor detail-
ing, etc.). It is essential that the interaction between the structure and
its environment is addressed when seeking to design durable struc-
tures. The influence of an aggressive environment on potentially
vulnerable and critical components can be reduced by appropriate
design. These issues would be considered in the 'conceptual design'
and 'detailed design' phases of the service life design process.
The required performance under the defined environmental loads.
Appearance or aesthetic requirements, both initially and through
■
life.
Requirements for usable space, dimensions, services and fittings.■■
■
The period of tenure and the requirements for the facility at the
■
end of this period.
Future changes of use to increase flexibility and minimise the risk
■
of obsolescence.
Restrictions to the design (e.g. planning regulations).
■
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