Column splice forces in moment frame

[BAGW]

Hi,

When designing column splice in moment frames (non-seismic region), is there a minimum force the splice needs to be designed for per AISC? Or can we look at the actual forces and design it for the those forces only?

I am concerned regarding amplification of drift due splicing of column.

 

[CANPRO]

I am not familiar with AISC, so I can't help with any specific code reference. With your concern about additional drift, it sounds like you're more concerned with connection stiffness than strength in this case. With increased strength demand on the connection you're going to get some inherent increase in your stiffness as well, but that does not guarantee a sufficiently stiff connection. For example, if you have a bolted flange plate splice but the connection does not provide a slip-critical condition, you have 1/16" oversize in the hole of each ply which would increase rotational displacement under bending. Depending on your section size, frame geometry, and drift limits, that could be significant.

If you're concerned about drift I suggest flange plate splices and design for slip-critical conditions with service loads. Strength designed to demand or code minimums. Another fun exercise in these kinds of situations is to play with the connection stiffness in the model of your structure and see how it impacts drift; this will give you a good indication about just how concerned you should be about the connection.

 

[milkshakelake]

I'd design for actual forces. It's not any different from the moment plate connection itself. You're not considering additional deformation there, so column splice should be treated similarly.

An argument could be made that you'd reduce the stiffness by designing for the actual forces instead of full column capacity. In that case, I might design it to have the same strength as the column. But then again, that logic doesn't apply to moment plates, so this shouldn't be any different. If anything, the moment at the column splice should be a lot less than at the moment plate, so it's less of a concern.