Yield line capacity vs. interaction with other stresses 2

[WARose]

I have a situation where I have a column that is receiving axial load and in addition, it also has a brace coming into its web (via a gusset). I have calculated the web capacity for the gusset based on (accepted) yield line theory. However this left me wondering (and not for the first time): should I reduce the yield line capacity for the web based on the other stresses in the column (from other loads)? In other words: are the other stresses in the columns taking away from the yield line capacity?

Thoughts?

 

[BAretired]

Yes, indeed. A plate stressed by one action cannot contribute full yield capacity to another action. They must be considered together.

BA

 

[dimvoly]

This isn't a response to your question, but don't forget the eccentric weak axis moment on the column due to the brace.

 

[WARose]

Yes, indeed. A plate stressed by one action cannot contribute full yield capacity to another action. They must be considered together.

That's kind of my p.o.v. on it too.....so I have used a reduced yield value in the equation I use. But sometimes I wonder if it is quite that simple.

 

[BAretired]

Might not be quite that simple, but I believe that the assumption of a reduced yield strength in the direction of the other applied stress is a reasonable precaution to take.

BA

 

[271828]

I'm leery of using YLA for this situation. The web deformation could be very large to achieve the yield line pattern. I realize the analysis is done with a virtual displacement which is arbitrary and small, but the pattern must be able to form for the analysis to be valid. Is it feasible to put stiffeners in the column, spanning between column flanges, to take the brace force instead?

 

[WARose]

In this particular situation, I am in a part of a chem plant where welding is just about impossible to do (and this is for an addition to an existing structure). But my question is as much for future reference as anything else because this isn’t the first time I’ve wondered on this one………and was hoping to hear from someone who knew more about yield line theory than I do.