Structural Design for Architecture
14
and parallel-sided, and which lend themselves
to use in straight-sided frameworks. Most steel
structures therefore have a regular, rectilinear
geometry. The range of possible forms has
been extended in recent years by the develop-
ment of techniques for bending rolled sections
into curved shapes and by the increased use of
casting to produce structural steel elements.
However, the fact that all steel structures are
prefabricated tends to require that regular and
repetitive structural geometries be adopted
even though the individual components are of
irregular or curvilinear shape.
A typical steel-frame building thus has a
relatively simple overall form and an interior
which is open and unencumbered by structural
walls. Great freedom is therefore available to
the designer so far as the internal planning of
such buildings is concerned: the interior
volumes may be left large or they may be
subdivided by non-structural partition walls;
different arrangements of rooms may be
adopted at different levels and a free choice is
available in the treatment both of the external
walls and of the internal partitions.
An advantage of prefabrication is that steel
structural elements are manufactured and pre-
assembled in conditions of very high quality
control. Great precision is possible and this,
together with the slenderness which results
from high strength, means that structures of
great elegance can be produced. Steel is there-
fore frequently selected as much for its
aesthetic qualities and for the stylistic treat-
ment which it makes possible as for its struc-
tural performance.
Reinforced concrete, the other 'strong'
material, is of lower strength than steel with
the result that equivalent structural elements
are more bulky. It too is used principally in
skeleton-frame structures of regular geometry
and therefore offers similar advantages to steel
in respect of internal planning and exterior
treatment.
Concrete structures are normally manufac-
tured on the building site by the pouring of
liquid concrete into temporary formwork struc-
tures of timber or steel which are specially
made to receive it. This allows a wide choice of
Fig. 1.17 Goetheanum, Eurhythmeum, 'Glashaus' studio,
Dornach, Switzerland, 1924-28. Rudolf Steiner, architect.
The complexity of form which is possible with in situ
reinforced concrete is well illustrated here. [Photo: E. & F.
McLachlan]element shape to be available. Continuity
between elements is also easily achieved and
the resulting statical indeterminacy^5 facilitates
the production of structures of complicated
form. Irregular geometries in both plan and
cross-section, with cantilevering floor slabs,
tapering elements and curvilinear forms may
all be produced more easily in reinforced
5 See Macdonald, Structure and Architecture, Appendix 3, for
an explanation of the phenomenon of statical indeter-
minacy and its relevance to the determination of struc-
tural form.