Structural Design for Architecture
12
Fig. 1.14 Palmerston Special School, Liverpool, England,
1973-76 (demolished 1989). Foster Associates, architects;
Anthony Hunt Associates, structural engineers. Semi-form-
active portal frames of steel hollow-section are used here
as the primary structural elements in a multi-bay arrange-
ment with relatively short spans. The moderately high
efficiency of this type of structure has permitted very
slender elements to be adopted. |Photo: lohn Donat]
susceptibility to both physical and chemical
deterioration) and performance in fire. Non-
physical, but interrelated, properties which are
relevant are cost, availability and environmen-
tal impact. The last of these is concerned with
the environmental issues (depletion of mater-
ial resources and energy sources, pollution, the
health of workers, etc.) which will arise from
the manufacture, installation and use of struc-
tural elements of a particular material.
Of the purely physical properties, perhaps
the most important so far as structural per-
formance is concerned is strength, although
the ratios of strength to weight and strength to
elasticity are also significant because these
determine the efficiency with which a material
can be used. Of the four principal structural
materials, steel and reinforced concrete may
be thought of as high-strength materials and
timber and masonry as low-strength materials.
Each of the four has a unique combination of
properties which makes it perform best in
particular types of structural arrangement.
Another set of factors which influences the
types of structure for which a material is
suitable are the conditions of its manufacture
and finishing. These determine the type of
product in which the material becomes avail-
able to the builder. Steel, for example, is avail-
able in the form of manufactured elements
which are straight and of constant cross-
section. The construction of a steel structure is
therefore a process of assembly of prefabri-
cated components. Concrete, on the other
hand, normally arrives on a building site in
liquid form and the building is literally formed
