Structural Design for Architecture
Fig. 5.32 Individual plane walls are ineffective at resist-
ing out-of-plane loads but can resist in-plane loads.in other words, contain a structural system
which is capable of conducting the lateral
loads from the points at which they are
applied, to the foundations, where they can
ultimately be resisted (Fig. 5.31). This property
will also guarantee stability, as noted above.
Secondly, the horizontal load subjects the
external walls to out-of-plane forces which they
are ill equipped to resist, due to their low
strength in bending (Fig. 5.30b). Provision
must therefore be made either to give them
the necessary strength to resist these loads or
to provide them with lateral support.5.3.3.2 The lateral strength of the building,
taken as a whole
The strategy which is adopted to provide a
masonry building with lateral strength, and
therefore also stability, is usually based on the
very good performance of walls in resistance to
in-plane forces (Fig. 5.32). Buildings are there-
fore planned so that wind forces are conducted
to the foundations by walls which are more-or-
less parallel to their direction.^7 This means
that walls must be provided in two orthogonal
directions on plan. In practice, it is rarely diffi-
cult to achieve this because the space-7 The building must obviously be capable of resisting
wind load from any direction. This condition is satisfied
172 if resistance is provided in two orthogonal directions.Fig. 5.33 This cross-wall arrangement required non-
loadbearing bracing walls for stability.planning requirements of masonry buildings
will normally produce a plan which contains
walls which run in the two principal directions,
even though the primary loadbearing walls
may be parallel to each other in only one of
these. The plans in Fig. 5.24, for example, are
satisfactory in this respect. Figure 5.33a shows
an arrangement which is not satisfactory
because there is no wall which can resist wind
load as an in-plane force in one of the build-
ing's principal directions. Additional walls
must therefore be added to render the building
stable (Fig. 5.33b).
The horizontal parts of masonry structures
play an important part in the resistance of
horizontal load and they can act in two capaci-
ties. For a particular direction of horizontal
load they provide a direct tensile or compres-
sive link between bracing walls and other walls
which require to be stabilised. They can also
act as horizontal-plane bracing (Fig. 5.31).
Normally the horizontal structure in a masonry(b)(a)