cmaa 70 beam local buckling

huangyhg

cmaa 70 beam local buckling
i want to check for buckling of a crane rail beam. i am using cmaa 70, section 3.4.8. the first formula uses a buckling coefficient, k (either compression or shear) and referes to table 3.4.8.2-1.
1) for i beams, is length "a" the width of the flange?
2) for i beams, is length "b" the distance between flanges?
3) what about square tube beams?
4) how do i determine ? (psi)?