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Chapter10 Ultimate Strength of Plates and Stiffened Plates 207
(10.20)
where,
G~ = Axial stress in direction 1
Q2 = Axial stress in direction 2
? = Shear stress
b~~ = Limiting axial stress for oI
= Limiting axial stress foro,
‘L = Limiting shear stress
Following Bai (2001), the following strength criteria may also be applicable for ultimate
strength (of plates or stiffened plates) under combined loads:
(10.21)
where,
p = Lateral pressure
PL = Limiting lateral pressure
Eq.(10.21) has been proposed because it approaches to von Mises yield conditions for inelastic
buckling cases and may lead to linear interaction for elastic buckling cases. According to API
2V (1987), the coefficient a may be taken as 0 when both stresses 6, and o, are compressive,
and as 1 when either 6, , u2 or both are tensile. To be accurate, the coefficient a should be
derived based on finite element analysis and mechanical test.
10.3 Buckling Strength of Plates
Johnson-Ostenfeld formula (or Odland, 1988) may be applied for plasticity correction. To
calculate elastic buckling stress under combined loads, the equations in Section 10.2 may be
used. The elastic buckling strength for plates under compressive stress and in-plane bending
may be expressed as
(1 0.22)
An expression giving good accuracy with the exact elastic buckling solution for a simple
supported plate exposed to pure shear stress is given in Timoshenko and Gear (1961),
(10.23)
where
