STRUCTURAL DESIGN FOR ARCHITECTURE

Depth of main frame (mm)

Span (m) Solid web Plane truss Space truss

10 450 1000 1000

15 600 1200 1200

20 700 1400 1400

30 900 1800 1600

40 1200 2500 2200

50 - 3000 2800

60 - 4000 3800

70 - 5000 4800

80 - 6000 5500

100 - 8000 6000

Main Frame

Span, Spacing, Height, Rafter Depth

L S H depth at knee

(m) (m) (m) (mm) (mm)

10 3 6 300 600

15 4 7

20 5 8 450 800

25 6 9

30 7 10 550 1050

35 8 11

40 9 12 600 1200

45 10 13

50 10 14 700 1350

55 12 15

60 12 16 750 1600

Table 3.5 Approximate depths and span ranges
for trusses of hot-rolled sections in single-storey
steel frames

Table 3.6 Approximate span ranges and element

dimensions for steel portal frameworks

Steel structures

elevational roof geometries can be adopted but
a regular plan layout must normally be adhered
to. Table 3.5 gives an indication of the depths
required for the primary elements in parallel
chord arrangements. Approximate sizes for
portal frameworks are given in Table 3.6.
Frames of this kind are constructed with both
rigid and hinge-type joints and the bracing
requirements are dependent on the particular
configuration of joints which is adopted. A
common arrangement is illustrated in Fig. 3.32.

3.6.2.3 Two-way-spanning systems

In two-way-spanning systems primary elements

are provided in two principal span directions.

The structure can take the form of intersecting

sets of single-plane elements, such as triangu-

lated trusses (Fig.. 3.33), or of a fully three-

dimensional triangulated space framework

(Fig. 3.34).

Fig. 3.32 Bracing of single-storey frameworks, based on strong, hot-rolled primary elements.
(a) This is a typical bracing arrangement for a portal-frame structure. The frame is self-bracing, by rigid joints, in the
across-building direction but triangulated bracing girders are required in the vertical and roof planes adjacent to the ends
of the building to guarantee stability in the along-building direction.
(b) Where a framework is not self-bracing in the across-building direction an arrangement of bracing girders must be
provided in both horizontal and vertical planes. 79