doube angle column intermediate connectors

huangyhg

doube angle column intermediate connectors
the table 4-8 (double angles in axial compression) in the aisc 13th addition steel manual gives the number of connectors needed between angles.  can somebody explain to me why the number of connector say for like a 2ll6x6 column is 2 no matter if you have a 2' long column or a 40' column???  
see the foot notes and the information about table 4-8 at the beginning of the chapter.
i did read that information at the beginning of the chapter but the connectors shown on the load tables still makes no sense.  i understand that you can use less by computation.
i know the 9th edition had a requirement that a minimum of two spacers be provided.  interestingly, i do not see that in the 13th edition.
i will study the issue a little and see if i can provide a clearer answer.  i think that local buckling controls for buckling about the x-x axis, and that adding additional connectors doesn't decrease the local buckling.