STRUCTURAL DESIGN FOR ARCHITECTURE

Fig. 3.50 Where long spans

require the use of deep tri-

angulated girders this can

greatly increase the struc-

tural depth of the floors. The

two systems shown here

allow deep girders to be

accommodated without an

increase in storey height.

The penalty which is paid for

this is that it places restric-

tions on space-planning.

Structural Design for Architecture

provided in the form of self-supporting cores

of masonry or reinforced concrete (Fig. 3.54),

which are normally constructed in advance of

the erection of the steelwork and which are

used to carry vertical as well as horizontal

loads.

The reinforced concrete floors of the struc-

ture are usually capable of acting as horizon-

tal-plane bracing and the need for this does

not usually affect the general planning of the

building. Where a lightweight roof cladding is

used, a horizontal-plane girder (normally of the

triangulated type) is provided at the topmost

level but this can be accommodated within the

roof structure and does not usually present a

planning problem.

To sum up, two factors must be considered

in the planning of low- or medium-rise multi-

storey frames. These are firstly, the geometry of

the floor grid and its relationship to the

column grid and secondly, the provision of

bracing. A general arrangement must be

devised which both produces a satisfactory

structure and allows the space-planning

requirements of the building to be met.

3.6.3.4 Multi-storey frames with special geom-

etries

Although most of the steel frames which are

constructed in practice have characteristics

which are similar to those which are described

above, the need for a frame which has quite

different characteristics does sometimes arise.

Fig. 3.51 Typical arrangement of joints in a hinge-jointed

multi-storey framework.

The disposition of the vertical-plane bracing

is a factor which affects the general planning

of the building. It is normally positioned in as

symmetrical an arrangement as possible and

convenient locations for diagonal bracing are

the perimeter walls or around stair wells, lift

wells and service cores (Fig. 3.53). If

92 diaphragm bracing is used it is frequently

Staggered Interstitial