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208 Part I1 Ultimate Sh-ength
(3
k,=4.0 - +5.34 (10.24)
0 =Poisson’s ratio
0-
Yield stress in shear may be estimated as 2 where go =yield stress of the plate.
&
10.4 Ultimate Strength of Un-Stiffened Plates
10.4.1 Long Plates and Wide Plates
Slender plates can carry loads larger than what is predicted by elastic theory if their unloaded
edges are constrained to remain straight. Because of large lateral deflections, membrane
stresses develop in the transverse direction, which tend to stabilize the plates. At this stage, the
distribution of stresses along the unloaded edges is no longer uniform but rather, it increases
towards the stiffeners. According to the effective width method, the ultimate strength is
obtained when the edge stress, oe, in Figure 10.8, approaches the yield stress. The following
formula has been widely used for simply supported plates where the unloaded edges are
constrained to remain straight (Faulher, 1975).
(1 0.25)
where the plate slenderness ratio is given by,
(10.26)
/ n
Figure 10.8 Actual Stress Distribution in a Compressed Stiffened Plate
Eq. (10.35) accounts for a reasonable degree of initial deflection in the buckling mode, but
does not account for residual stresses.
