The Australian Bridge Design Code gives the following formula for a reinforced concrete column:<br>
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Nc = (pi^2/Le^2)*(200*d*.6*Mub)/(1+Beta_d) where<br>
<br>
Nc = Buckling load<br>
Pi = pi or 22/7<br>
Le = effective length of column<br>
d = depth to outermost layer of tensile steel<br>
Mub = moment corresponding to nuetral axis depth of 0.6*d<br>
Beta_d = ratio of dead load to total load.<br>
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Hope this helps!<br>
Bridgeman<br>