STRUCTURAL DESIGN FOR ARCHITECTURE

Structural Design for Architecture

5.3 The basic forms of masonry

structures

5.3.1 Introduction

There are two basic types of masonry: plain

masonry, in which bricks or blocks are simply

bedded in mortar to form walls and piers, and

reinforced masonry, which contains steel

reinforcement bars in addition to the

constituents of plain masonry (Fig. 5.36).

Reinforcement bars provide tensile strength

and produce a material whose structural

properties are similar to those of reinforced

concrete. Reinforced masonry tends to be used

in conjunction with plain masonry in situations

where walls are required to have flexural

strength, such as where they are exposed to

large out-of-plane loads. Its presence tends to

have only a modifying effect on the forms of

masonry structures, whose basic geometries

have been determined by the properties of

plain masonry.

In common with all buildings, loadbearing

masonry structures must be capable of resist-

ing two principal types of load: gravitational

load, caused by the weight of the building and

its contents, and horizontal load, caused by

the action of the wind or of earthquakes. A

number of form-determining factors result

from this; the influences of each load type are

considered separately.

5.3.2 Resistance to gravitational load

5.3.2.1 Introduction

The strategy for resisting gravitational loads in

masonry structures is to use a post-and-beam

arrangement in which the masonry forms the

vertical elements and the horizontal elements

are made from some other material, usually

timber or reinforced concrete (Fig. 5.20). Two

factors play a dominant role in determining the

arrangement of walls which must be adopted.

Firstly, the plan-form must be such as to

provide support for all areas of floor and roof

which have to be carried; this is the more

important factor. Secondly, the walls must

have adequate strength; they must not be

over-stressed by the loads which they carry and

neither must they become unstable by

buckling. The second set of considerations

tends to affect the thickness of walls rather

than the plan-form of the building, but the

need to provide lateral support to prevent wall

buckling can affect the latter.

5.3.2.2 Provision of support for floors and roofs

The wall arrangements which are adopted to

Fig. 5.20 Typical arrangement of structural elements in a

loadbearing masonry building. The timber floor structures

are carried on a parallel arrangement of loadbearing walls.

The trussed-rafter roof, which is a more efficient type of

structure than the rectangular cross-section floor joists

and which carries less load, spans across the entire width

of the building between the exterior walls. Additional non-

loadbearing walls (not shown) are required in the across-

164 building direction for stability.