Good afternoon guys. I am still working with this 42" UG pipeline that I wrote about earlier. The client has called for slip joints to reduce the stress levels such that OPE is <= 60% of Sc. The pipe is A36, spiral-welded.

I have modeled the slip joint per the Applications guide. Now for the dumb question. When I apply the axial thrust force, which is 160k, don't I need to apply it equally and in opposite directions on either side of the joint? I drew a FBD of the pipe around the joint and I think I do need to apply it in both directions, equal and opposite.

It's amazing the fundamentals that one forgets when allowing software to do one's thinking for them...

Thanks!!
Pete

If you specify an effective inside diameter in defining an expansion joint (you may be doing this or you may be building your slip joint by hand with "CNoded" restraints), CAESAR II will add those effective thrust loads on either side of the joint. A more correct model would have you apply those thrust loads on those upstream and downstream surfaces normal to the axis of the slip joint.

It could make a difference.

Search this forum for "thrust load" or something like that. There was an earlier thread that took up this issue.

Thanks Dave. After some thought, that is what I did.

After some thought I convinced myself that both forces do have to be present for the joint (the system) to be in equilibrium.