STRUCTURAL DESIGN FOR ARCHITECTURE

Fig. 5.35 Plans of walls showing various arrangements for incorporating vertical reinforcing bars. These give the walls

the ability to span vertically between floor and roof structures in response to out-of-plane loads.

that the second moment of area^8 of the wall

cross-section is maintained high, by making

the wall reasonably thick.

Masonry, as mentioned above, can be given

the bending strength which is necessary to resist

high out-of-plane load by reinforcing it with

steel bars. Its behaviour is then similar to that of

reinforced concrete. The technique is usually

used to augment the strength of walls which

must carry very large bending loads, such as

retaining walls or the external walls of high

buildings. Vertical bars provide the bending

strength to span vertically in response to out-of-

plane forces. These must either be incorporated

into the voids of special bricks or blocks, or

accommodated in vertical channels provided by

special bonds (Fig. 5.35). Walls can also be given

the strength to span vertically by incorporating

reinforced concrete or steel columns into them.

Horizontal bars in the bedding joints of masonry

or within special blocks (Fig. 5.36) give walls the

strength to span horizontally. These techniques

do not affect the overall form which must be

adopted for a building, except insofar as they

permit large areas of plane wall to be adopted.

5.3.3.4 Summary of form determining factors

which result from the need to resist horizontal

load

The principal features which are incorporated

into the geometries of masonry buildings in

order that they can resist horizontal load effec-

tively are as follows.

Fig. 5.36 Incorporation of reinforcement into the

bedding planes gives masonry the ability to span horizon-

tally between buttressing walls in response to out-of-plane

loads.

1 The plan must contain walls orientated in

two orthogonal directions.

2 The horizontal parts of the structure must

provide an effective structural link between

the walls. They must therefore have

adequate strength and must be adequately

fixed to the walls.

3 The walls are disposed in as symmetrical an

arrangement as possible on plan. This is not

essential in low-rise buildings, where wind

loads are small, but becomes increasingly

174 important as building heights increase.

Structural Design for Architecture

Reinforced, tied

and grouted

cavity wall

Reinforced

pocket

Quetta bond Vertical slot

wall wall

Pocket wall Cavity wall