huangyhg

restraint at top of column
i've got an unusual situation for supporting a wall mounted jib crane and wanted to see if some others in the forum could offer suggestions or maybe have encountered something similar in the past.
the building column is not strong enough to support the jib crane (the column is built from cold formed cees). what i'm proposing to do is design the column as some what free standing. i say "some what" because of what i'm debating designing for the restraint at the top of the column. basically the cold formed cee building column is about 14 inches behind a much more robust buidling with concrete columns (plan dimensions of the concrete column are 24"x25.5"). the new jib crane column would be slightly offset from the centerline of the concrete column but not much. the weak axis of the jib crane column would be braced to this concrete column at each point where the pull and thrust forces occur. the weak axis is perpendicular to the building column line of the concrete columns. based on the stiffness of these joints and concrete column, i would consider k=1.0.
how to restrain the strong axis is where i'm indecisive. i've looked at the strong axis as a flagpole (k=2.1), but the resulting base fixity would be hard to achieve. what i'd like to do is come up with a way to restrain the top enough to consider the joint as rotation fixed and translation free thus designing for a k=2.0 with a pinned base. my thought is to run two members horizontally from each side of the concrete column and connect to the jib crane column. however, in order to do this, i'll probably need to connect a member horizontally across the top of the jib crane column to form a "t". each end of the horizontal top of the "t" would connect to the horizontal members from the concrete column. the horizontal members from the top of the "t" to the concrete column would be designed to be stiff enough so that the joint cannot rotate. this would basically look like a horizontal moment frame at the top of the jib crane column.
any comments, suggestions or alternate ways to brace the top of this column would be greatly appreciated.
from your post, i don't think you really need any help. you are approaching the jib column installation just as i would.
thanks for the reassurance.

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