STRUCTURAL DESIGN FOR ARCHITECTURE

Fig. 6.50 Timber wallframe - modified frame type. In the

modified frame the wall elements are only one storey high

but the floor joists are attached directly to them. The

modified frame is a compromise between the platform and

balloon arrangements which combines some of the advan-

tages of both.

Fig. 6.51 Timber wallframe - the independent frame

type. In the independent frame the wall elements are one

storey high but the floor joists are carried on a steel angle

attached to the inner face of the wall. This arrangement

lends itself to prefabrication. The fact that the floor joists

do not penetrate the outer wall improves the thermal

efficiency of the wall.

Fig. 6.52. Note that, as in the case of masonry

structures, spine- and cross-wall forms are

used. In spine-wall arrangements the roof

normally spans the full width of the building

and only the floors are supported on inter-

mediate walls. Cross-walls are normally used

in conjunction with purlin roof construction.

The wall-to-floor and wall-to-roof junctions

in this form of structure are non-rigid and

lateral stability is provided by the wall, floor

and roof panels themselves, which serve as

diaphragm bracing in the vertical and horizon-

tal planes. Care must be taken in the planning

of the buildings to ensure that vertical-plane

bracing is correctly positioned. Bracing walls

must be provided which are as symmetrically

disposed as possible on plan.

It is also necessary that both the wall and

the floor panels should have sufficient strength

to resist in-plane racking^7 caused by wind load.

This is done by sheathing with plywood or

some other form of composite board

7 The tendency of the original rectangular shape to

become a parallelogram due to shearing action. 223

Timber structures

Head binder

Head plate

Floor joists

Cavity barrier

Head plate

Sole plate

Floor joists

Sole plate

Cill plate

Base wall

Tongued

and grooved

boarding

Studs

Tongued

and grooved

boarding

Head binder

Head plate

Floor joists

Metal

connecting

plate-

Steel angle let

into face of studs

Floor battens

Damp proof

membrane

to concrete raft

Cill plate

Edge of concrete

Sole plate

Plywood

subfloor

Cavity

barrier

Head plate

Sole plate

Plywood

subfloor

Studs