RANKINE GORDAN FORMULA:
Predictions of buckling loads by the Euler formula is only reasonable for very long and slender struts that have very small geometrical imperfections. In practice, however, most struts suffer plastic knockdown and the experimentally obtained buckling loads are much less than the Euler predictions. For struts in this category, a suitable formula is the Rankine4ordon formula which is a semi-empirical formula, and takes into account the crushing strength of the material, its Young's modulus and its slenderness ratio, namely L/K, where
L = length of the stmt
k = least radius of gyration of the strut's cross-section
A = cross-sectional area
PR = Rankine-Gordon buckling load
Pc = Eulerbuckling load
where a is the denominator constant in the Rankine-Gordon formula, which is dependent on the boundary conditions and material properties.