Civil Engineering Reference
In-Depth Information
contracts and regions. However, this chapter follows common
UK building terminology, calling the stages in order:
cost, increases during this period. Properly executed concept
and scheme stages minimise the potential for later unnecessary
and disruptive costs as well as delivering a better building.
Whilst clients often recognise the need for an architect to
commit resources to the brief definition and conceptual stages
they are sometimes tempted to reduce the time and fees avail-
able for the engineers during this period to almost zero in the
belief that they will add little value at this early stage. There is
no doubt that an experienced architectural team can anticipate
many of the structural issues, layouts and zones for a 'con-
ventional' building but it is important that the future structural
team has 'buy-in' to these decisions, especially if there are any
unusual aspects to the project - and there often are.
The key issues that the structural engineer needs to investi-
gate, agree and define early in the design process are the ones
that affect cost, coordination with the other disciplines, the
programme and the procurement route. In particular, during
concept design these key issues might include:
Brief definition - understanding the problem.
■
Conceptual design - investigating the options and their impli-
■
cations.
Scheme design - choosing and laying out the best option.
■
Detailed design - producing all the information needed for con-
■
struction.
And finally, support for the construction process - responding to
■
problems experienced on site.
Common design life-cycles in the UK include those defined
by the RIBA (Royal Institute of British Architects), the CIC
(Construction Industry Council) and, for rail-related projects,
GRIP (Guide to Railway Investment Projects). The structural
team needs to understand the requirements of the system being
used by the project, the level of decision-making defined at
each stage both for structure and the other disciplines and the
requirements for their deliverables at these phases.
Design teams are sometimes tempted to try and jump
straight to a final form without a process of investigation, when
they narrow the options over time by increasing detail and cer-
tainty. By doing so they are likely not to have understood the
key structural and multi-disciplinary design drivers and will
deliver a non-optimal solution. Often an over-hurried choice of
solution will require the design to be changed later to accom-
modate issues missed due to the lack of investigation during
concept or scheme design.
Figure 7.1
1
shows the cumulative number of hours that the
structural design team might input into the design and delivery
of a building over a two-year process. It also shows how the
cost of any change to the building, be it design or construction
The loads to be carried.
■
The basic layout of the columns, defining the typical bay size.
■
The need for any transfer beams beneath columns.
■
The size and support of any cantilevers.
■
The depth of the zones available for the structure at each floor
■
level.
The arrangement on plan of the stability systems and whether
■
these can be moment frames cores with bracing or stability walls.
It can be seen that at concept stage these decisions do not neces-
sarily prescribe a specific solution type. Instead, they allow the
space and cost that will allow a reasonable, optimal solution to
later be developed at scheme design which can then go on to be
successfully detailed and then constructed.
Figure 7.1
Structural design time and the cost of change
