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Steel Designers Manual - TheBestFriend.org

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This material is copyright - all rights reserved. Reproduced under licence from The <strong>Steel</strong> Construction Institute on 12/2/2007<br />

To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.<strong>org</strong>/<br />

<strong>Steel</strong> <strong>Designers</strong>' <strong>Manual</strong> - 6th Edition (2003)<br />

section at support<br />

Fig. 17.7 Lateral torsional buckling<br />

V<br />

D<br />

Ètw(<br />

dw - hh)<br />

˘<br />

=<br />

t<br />

ÎÍ g mg f3 ˚˙<br />

l<br />

Design of steel bridges to BS 5400: Part 3 489<br />

Lateral restraint<br />

quarter length of buckled beam<br />

section at restraint<br />

(vertical displacement)<br />

support<br />

--<br />

1w<br />

section between restraints<br />

(vertical horizontal and<br />

rotational displacements)<br />

where tw and dw are the thickness and depth of the web respectively, hh is the height<br />

of the largest cut-out within the panel being considered, gm and gf3 are partial material<br />

and load factors respectively, and tl is the limiting shear stress. For slender<br />

webs tl is governed by shear buckling, which becomes significant in webs with depth<br />

to thickness ratios greater than about 80.<br />

The actual shear strength of a web panel is dependent on the following:<br />

(a) Yield stress (suitably factored)<br />

(b) Depth-to-thickness ratio of web<br />

(c) Spacing of stiffeners<br />

(d) Conditions of restraint provided by flanges

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