Local buckling of thin-plate elements - The Behaviour and Design of Steel Structures to EC3 - page 115

25

b

20

L

15

Approximations of
equations 4.22 and 4.23

10

5.34
1 buckle

5

2 buckles 3 buckles

0

0 1 2 3 4 5 6

Plate aspect ratio L/b

Figure 4.16 Buckling coefficients of plates in shear.

The values of the buckling coefficient k τ shown in Figure 4.16 and the form of
equation4.21indicatethattheelasticbucklingstressmaybesignificantlyincreased
either by using intermediate transverse stiffeners to decrease the aspect ratio L / d
and to increase the buckling coefficient k τ , or by using longitudinal stiffeners to
decrease the depth-thickness ratio d / t . It is apparent from Figure 4.16 that such
stiffeners are likely to be most efficient when the stiffener spacing a is such that
the aspect ratio of each panel lies between 0.5 and 2 so that only one buckle can
form in each panel.
Any intermediate stiffeners used must be sufficiently stiff to ensure that the
elastic buckling stress τ cr is increased to the value calculated for the stiffened
panel. Some values of the required stiffener second moment of area I st are given
in [3, 5] for various panel aspect ratios a / d . These can be conservatively approx-
imated by using

I st
at 3 / 12 ( 1 − ν 2 ) =

6
a / d

(4.26)

when a / d ≥ 1, and by using

I st
at 3 / 12 ( 1 − ν 2 ) =

6
( a / d ) 4

(4.27)

when a / d ≤ 1.