STRUCTURAL DESIGN FOR ARCHITECTURE

Fig. 4.41 Reinforced concrete stairs are simply one-way-
spanning slabs which span between the landings.

Fig. 4.42 Precast concrete flooring units. Precasting of

concrete allows higher levels of quality control than are

possible with in situ casting, which allows greater strength

to be achieved from a particular set of mix proportions.

This permits the use of reduced thicknesses for a given

load-carrying capacity and the use of more complex cross-

sections. The efficiency of the units depicted here is

improved by the introduction of voids into the core.

used in the context of heavily serviced build-
ings where the combination of structure and
services is desirable.
A wide variety of precast concrete propri-
etary components is currentlyavailable ranging
from simple rectangular-cross-section beams
or slabs (Fig. 4.42) to complete framing
systems for buildings (Fig. 4.43). In cases
where no proprietary system is available,
bespoke elements are used provided the scale
of the project is such as to justify the setting
up of the necessary production process.
Among the disadvantages of precasting are
the difficulties associated with connecting
elements together satisfactorily. Precasting
also favours the adoption of building forms
which are regular and repetitive because this
simplifies the erection process and allows
maximum advantage to be taken of
economies associated with the mass produc-
tion of identical units. The restrictions on
form which are associated with steel frame-
works are therefore also a feature of precast
concrete structures.

Fig. 4.43 Precast concrete framework. The precasting

technique can be applied to all types of structural element

and makes possible the construction of complete precast

frameworks.

Precast components are frequently

combined with in situ concrete and this allows

the advantages of both forms of construction

to be enjoyed (Fig. 4.44). The use of in situ

concrete at the junctions of precast frameworks

can solve the problems associated with joint-

ing the units together, particularly the 'lack-of- 133

Reinforced concrete structures