Structural Design for Architecture
possible, this must be achieved by the use of
substantial horizontal structure at the levels at
which discontinuities in vertical structure
occur. A deep structure will be required,
however, and appropriate provision for this
must be made.
If the form of a building is highly irregular in
plan, elevation or section an unconventional
form of structure will be required. This will
normally have to be based on either reinforced
concrete or steel - see above.2.3.5 Exterior treatment
The treatment which is envisaged for the
exterior of a building can affect the choice of
structure type, especially if large areas of the
walls will either be glazed or covered with a
cladding material which is incapable of acting
as part of the support structure. Full glazing of
the exterior walls, in particular, is normally
associated with a skeleton-frame structure. It is
worth noting, however, that this type of treat-
ment of the exterior need not, by itself, neces-
sarily dictate that a frame structure be adopted
as it is possible to arrange the plan of a
loadbearing-wall building in such a way that
the exterior walls are non-loadbearing (e.g.
with a cross-wall-type plan). Full glazing of the
exterior of a building is, however, normally
associated with a relatively open plan for
which a frame structure would in any case be
appropriate.2.3.6 Conclusion
The selection of the generic type of structure is
therefore based on a number of factors, the
most important of which are: scale, which
determines the spans involved; internal
planning which dictates the nature of the inter-
nal spaces required; and external treatment.
The structural choices available are form-
active, semi-form-active and non-form-active
structures, in all their manifestations. The final
selection will be determined by the issues of
cost and technical feasibility, given the
requirements of scale, space planning and
external treatment.17 Not because the material is inherently stronger but
because the volume of the structure itself, for a given
thickness of wall, is greater. The timber wall will consist
of a series of closely spaced vertical elements alternat-
ing with voids. The masonry wall is continuous and
therefore contains more structural material fora given
thickness.
18 Traditional half-timbered buildings were frequently
higher (six or seven storeys), especially in the towns of
northern Europe. These were based on very large
timber sections, however. This type of structure is very
rare in the present day.2.4 Selection of the structural
material
The choice of the structural material is another
fundamental decision in the planning of a
structure. It is an aesthetic as well as a tech-
nical decision. Each of the four principal
structural materials (steel, reinforced concrete,
masonry and timber) produces a building with
a distinctive visual quality.
The preferred generic type of structure will
also affect the choice of structural material and
indeed these two issues are frequently
resolved together. If, for example, a loadbear-
ing-wall structure is adopted this will favour
the use of either masonry or timber.
Reinforced concrete and steel would be the
normal choices for skeleton-frame structures.
If a loadbearing-wall structure is being used
for a domestic-scale building there may be
little to choose between masonry or timber
from the point of view of structural action. A
masonry wall will normally have greater
strength in relation to compressive load,^17
which means that the use of masonry is essen-
tial if the building has more than three
storeys.^18 It also favours the use of masonry in
situations where internal spaces are large
(greater than 8 m across) and in other situ-
ations, such as the adoption of an irregular
pattern of loadbearing walls, in which the
loads applied to individual walls are likely to
be high. Other considerations, such as local
availability of materials, speed of erection or
any requirement for the prefabrication of the40