Table 3.10 Typical element sizes in multi-storey steel frameworks
Floor Floor beam depth (mm) Column cross-section
beam (H-section or square
span I-section I-section in Castellated hollow section) (mm)
(m) composite Storey height (m)
structure
3 4 5 6
4
6
8
10
12
14250
400
530
760
900
900200
380
450
600
760
830550
600
900
1150
1370150
150
200
200
250
250150 150
200 200
200 200
250 250
250 250
250 300150
200
250
250
250
300building so that the girders can be incorpor-
ated into walls, as in the staggered-truss and
interstitial-truss systems (Fig. 3.50).3.6.3.3 Bracing systems for medium-rise, multi-
storey frames
As in the case of single-storey frames multi-
storey frames can be of either the 'simple' or
the rigid type. Where the joints are rigid, the
frame is self-bracing and the need to provide
lateral stability is not a major factor in the
determination of the overall form. Where
hinge-type joints are used it is normal practice
for all beam/column connections to be of the
hinge type and for the columns to be jointed at
every second storey level, also with hinge
joints (Fig. 3.51). This fully hinged configur-
ation has a number of advantages: it simplifies
both the analysis and the erection of the struc-
ture, and it also allows the accommodation of
thermal expansion and minor foundation
movements without the introduction of stress
into the steelwork. In its basic form this type of
frame is highly unstable, however, and
additional bracing must be provided.
To render the 'simple' type of frame stable, a
limited amount of vertical-plane bracing, of the
diagonal or diaphragm types, must be incorp-
orated into the arrangement in two orthogonal
(mutually perpendicular) directions and this
must be linked to all other parts by horizontal-
plane bracing at every level. The action of a
multi-storey frame in response to wind loading
is shown diagrammatically in Fig. 3.52. 91Steel structuresFig. 3.49 Where long spans are required in multi-storey
frameworks it is normal to provide a tertiary system of
beams. In the example illustrated, triangulated girders,
spanning the entire width of the building (shown dotted
on the plan), are substituted for the columns at points A.
[after Hart, Henn and Sontag]
which is created within the building. Where
very deep lattice girders are involved, for
example, the depth of these can sometimes be
made the same as the storey height of the