Crippling Failure Part 2

One of the most common equation for crippling is shown below:

Fcc = (Ce*(Fcy*Ec)^0.5)/(b'/t)^3/4

Where
Fcc = Allowable crippling stress
Fcy = yield compression stress allowable
Ec = elastic modulus of material in compression
Ce = material boundary coefficient
b'/t = equivalent width over thickness ratio

Reference: Practical Stress Analysis for Design Engineers, Jean-Claude Flabel

As mentioned in the part 1 post of crippling failure, you can observed from the crippling allowable equation that it is not a function of length but only a function of material properties and width/thickness ratio whereas buckling is a function of length. This is an important distinction between crippling and buckling. For clarity the Euler column buckling equation is shown below:

Pcr-buckling = (Pi^2*E*I)/L^2

Where
Pcr = Critical buckling load
E = Elastic modulus of material in compression
I = moment of inertia about the failure axis of the column
L = column length

The above buckling equation is based on a pinned-pinned type boundary column. As shown the buckling is a function of column length.

Example Problem:

Assuming a flange with a width of 1.2 in and a thickness of 0.1in thick. The crippling allowable stress can be calculated:

Ce = 0.317 (1 edge free aluminum - Ref Flabel)
Fcy = 34 ksi (2024-T3 ref MMPDS)
Ec = 11.0 x 10^6

Fcc = 0.295*SQRT(34000*11*10^6)/(1.2/0.1)^(3/4) = 27.9ksi

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