Effective lenght factor

[beamblanck]

Often many people say to me that sap do many mistake in elaborate the effective lenght factor.
i would like to know how to make things right.
for example..
If i have something similar to this frame..

..that is loaded by some heavy cilynders, i would like to know how to set as effective lengt factor around x axis and y axis..

i hope to be clear..
many thanks
Alberto