Page 173 - Introduction to Naval Architecture
P. 173
STRENGTH 159
Figure 7.15 Comparison of strut formulae
The Euler and Rankine-Gordon formulae are compared in Figure 7.15.
At high slenderness ratio the two give similar results. At low slenderness
ratios failure due to yielding in compression occurs first.
In considering the buckling strength of grillages the strength of the
stiffening members must be taken into account besides that of the
plating. The stiffening members must also be designed so that they do
not trip. Tripping is the torsional collapse of the member when under
lateral load. Tripping is most likely in asymmetrical sections where the
free flange is in compression. Small tripping brackets can be fitted to
support the free flange and so reduce the risk,
Example 7.4
In Example 7.2 on the aluminium superstructure determine
whether a transverse beam spacing of 730 mm would be adequate
to resist buckling.
Solution
Treating the new transversely stiffened deck as a broad panel and
applying Euler's equation for a strut, its buckling stress is given by
the formula:
Taking Poisson's ratio, v, as 0,33 the critical stress is:
