Steel Designers Manual - TheBestFriend.org

This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007
To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/
Steel Designers' Manual - 6th Edition (2003)
0 Li
\\\\\\
_ JL
TI _ _
(1) (g) (h) (I)
Design considerations 403
(a) (b) (c) (d) (e)
Fig. 15.1 Typical column cross sections
(1) light trusses and bracing – angles (including compound angles back to back)
and tees
(2) larger trusses – circular hollow sections, rectangular hollow sections, compound
sections and universal columns
(3) frames – universal columns, fabricated sections e.g. reinforced UCs
(4) bridges – box columns
(5) power stations – stiffened box columns.
15.3 Design considerations
The most important property of a strut as far as the determination of its loadcarrying
capacity is concerned is its slenderness, l, defined as the ratio of its effective
length, LE, divided by the appropriate radius of gyration, r. Codes of practice
such as BS 5950 used to place upper limits on l, as indicated in Table 15.1, so as to
avoid the use of flimsy construction, i.e. to ensure that a member which will ordinarily
be subject only to axial load does have some limited resistance to an accidental
lateral load, does not rattle, etc. Although not now explicitly stated in the
2000 version of the code, it is still good practice to aim for robust construction.
Similarly, for BS 5400: Part 3, no actual limits are specified but the user is provided
with a general advisory note to the effect that construction should be suitably
robust. By contrast, BS 5400 does place upper bounds on local plate slenderness to
avoid consideration of local buckling (see Table 15.2).
Strut design will normally require that, once a trial member has been selected and
its loading and support conditions determined, attention be given to whichever of
the following checks are relevant for the particular application: