In general, it is not advisable to count on perfect fixity in steel connections, save if undeformable stiffeners are provided.

The thickness and spacing of the transverse plates for the built-up column must be calculated.

As a reference, their thickness is in the order of 5/16 in., with a width of 6 in., and a spacing between 2 ft. and 3 ft.

Pay attention to the eccentric connection of the beam on one channel.