Fig. 3.28 Single-storey frameworks
based on lightweight joists can be
braced by the rigid-joint technique.
The rigid joints can be either at the
bases or at the tops of the columns.
All columns must normally be
braced, however.The size of the column grid depends on the
type of structural element which is specified;
the normal range is from approximately 6 m X
6 m to 10 m X 25 m with element spacings of
around 1.5 m to 2 m. The columns are usually
hot-rolled sections, either universal columns
or rectangular hollow sections. Approximate
sizes for the normal span range of this type of
structure are given in Table 3.4.
Both self-bracing and braced versions of this
configuration are possible." Self-bracing
frames have either rigid column base connec-
tions or rigid beam/column joints (Fig. 3.28).Where hinge-type connections are used,
bracing in both horizontal and vertical planes
is required and diagonal bracing can be used
for both (Fig. 3.29). Diaphragm bracing is an
alternative, however. In the vertical plane this
can be provided by masonry walls, if these are
adequately tied to the columns, and in the
horizontal plane the roof decking can perform
this function, where it has sufficient strength.
Figure 3.30 shows a typical plan layout, with
typical span ranges, for a single-storey frame in
which the primary elements are arranged at
fairly wide spacings and a secondary structure,
on which the roof cladding is mounted, is
provided to link them together. The primary
elements must be stronger than in the previous
type of frame and hot-rolled sections are11 For a more detailed explanation of the bracing require-
ments of frameworks see Macdonald, Structure and
Architecture, Section 2.2. 77Secondary beam Secondary beam Secondary beam Column spacing. Column width Column height
span, L (m) spacing, P (m) depth (mm) S (m) (mm) (m)
4 1.0 200 3 50 3.0
5 1.0 200 3 60 3.0
6 1.5 250 4.5 70 3.5
7 1.5 300 4.5 70 3.5
8 2.0 350 6 90 4.0
9 2.0 350 6 90 4.0
10 2.0 400 6 90 4.0
12 2.5 550 9 100 5.0
14 2.5 600 10 150 5.0
16 3.0 700 12 150 5.0
18 3.0 800 12 150 5.0
20 3.0 900 15 180 5.0
22 3.0 1100 15 180 6.0
24 3.0 1300 18 200 6.0
26 3.0 1500 18 250 6.0
28 3.0 1600 24 250 6.0
30 3.0 1800 24 250 6.0Table 3.4 Span ranges and typical element sizes for lightweight steel joists in single-storey frame
structures
Steel structures