"K" factor for beam with fixed ends to horizontal pipes

[AggieYank]

For a beam with moment connections to horizontal pipes (or tubes), would you use less than 1.0 for "K"?

The way I see this working is to get a rotational stiffness based on torsion for the beams on each end and use that stiffness as my "G" for use in the C2 alignment chart (sidesway inhibited).

Conservatively it could be taken as 1.0, but I have a situation where we're looking for whatever we can get.

 

[Lion06]

do you mean a column with moment connections to horizontal pipes?
If so, as long as they aren't part of the lateral system, then you can use K=1.0 as a max and reduce based on Gtop and Gbottom using the alignment charts.
If it is part of the lateral system, then you have to use the appropriate alignment chart (depending if you have a sway frame or not.
I am assuming it is not part of the lateral system or it would be connecting to something more substantial than pipes.

 

[haynewp]

I would try it, as long as you are confident in the K=1.0 and looking to reduce the effective length further by including the torsion restraint. I would try to see what the torsional rotation of the beams would be given a unit rotation where the column member connects.

The more difficult part for me would be making sure I am using a reasonable comparison between the stiffness of the torsional restraint of the beams compared to that of the columns. If you look into the derivation of the slope deflection equations, K is a relative flexural stiffness. In other words, if I took the EI/Lcol divided by the torsional stiffness of the beams to get G at each end, I am not sure I am making an apples/apples comparison. But I may be wrong, I have never tried this problem before.

 

[AggieYank]

Thanks StructuralEIT and haynewp. This is indeed a beam. It is under an axial compression load and bending. The K factor goes into solving for the allowable compression in the interaction equation.

 

[Lion06]

Ok, that makes a littlemore sense then. Do you have a reasonable way to make a good moment connection from the beam to teh pipes? Is it a WF beam going to the pipes? Are they roughly the same depth? You could see some benefit from this depending how long the pipes are. The longer they are, the less torsional stiffness they will provide.