Pedetal with multiple columns

[LOKSTR]

I have a big concrete pedestal( 15' x 15'x 23' high) carrying four column(posts) of a space truss( Pre-Engineered building). Some column loads are compressive and some are uplift for same load combination.
What is general practice to design pedestal for this type of mixed loading? (I have designed pedestals having one column only)
Can I combine all the loads and design my pedestal for "NET" load both for shear and axial or it needs to be treated differently.
This is bulk storage building with barrel Vault space truss roof(Arched roof).

 

[slickdeals]

Yes, I would think you can sum the moments about the center of the pedestal and design for the net force and associated moments and shears. You would design each column to pedestal for its own forces.

It’s no trick to get the answers when you have all the data. The trick is to get the answers when you only have half the data and half that is wrong and you don’t know which half - LORD KELVIN