STRUCTURAL DESIGN FOR ARCHITECTURE

Structural Design for Architecture

202

composite construction. It is ideal for shear

panels such as the webs of built-up-beams

(Fig. 6.25) or the skins of wall or floor panels

which are used for diaphragm bracing. It is

also used as the flanges in stressed-skin panel

structure (Fig. 6.40).

6.6.2.3 Particle boards

Particle boards have traditionally been little

used as structural components and no data for

them are given in BS 5268. There is an increas-

ing tendency for these to be used in the struc-

tural role, however, particularly as a substitute

for tongued-and-grooved floor and roof

decking.

6.6.3 Built-up-beams

6.6.3.1 Introduction

Built-up-beams are components in which a

number of separate planks or boards are

assembled, by gluing, nailing, screwing, bolting

or a combination of these, to form beams of

composite cross-section. Various types of

built-up-beam are produced and these are all

intended to exploit the good structural proper-

ties of timber and to overcome the size restric-

tion which is inherent in the use of solid

sawn-timber elements. They are normally used

in forms of construction which are similar to

those which are suitable for sawn timber (i.e.

as joists in the traditional forms of floor and

roof structures - see Fig. 6.41) and they allow

longer spans to be achieved than are possible

with solid sawn-timber. Some of the more

commonly used forms of built-up-beams are

reviewed briefly here.

6.6.3.2 Laminated timber

Laminated timber, which is also called

'gluelam', is a product in which elements with

large rectangular cross-sections are built up by

Fig. 6.21 A selection of timber composite boards.

Traditional plywood

Four-ply plywood

Six-ply plywood

Three-ply blockboard

Five-ply blockboard

Laminboard

Composite panels