Hello,

I feel this is be simple, but I have a nagging uncertainty I want to quash.

An anchor flange that is pulling on some pipe, to offset some of the displacement behind the flange, should be represented by a guide and a displacement, right? Or is there a better way?

Thanks.

No.
If its a forced displacement, then you would have to "force" the system by using the "Displacement" option.

When you use a guide with gap (it is not displacement), it tells the software that the pipe is allowed to move by that value.

Hope I interpreted your query correctly.

I meant a combination of the Displacement option and a guide to represent the bracket holding the anchor flange. Though, is suppose the guide would only be needed if it would be engaged. I don't think the anchor flange is moving that much to the side.

I'm not entirely sure what you mean by anchor flange, but it sounds like just an attachment to prevent thermal growth beyond a certain amount. To that end, it would just be a limit with a gap (with appropriate stiffness as needed).

If, instead, your anchor flange is providing an external force to the pipe in the ambient condition, this is called applying cold spring, which is generally impermissible in order to obtain a passing design. However, that does not mean that you shouldn't calculate cold spring effects, particularly in existing piping where it is known to exist.

If you are, then you should estimate cold spring force and apply the appropriate displacement onto the pipe, with a limit of corresponding stiffness (and gap, if applicable).

Edit to add:
•Whether or not your flange has a guide is ancillary to the main question. If it has a guide, include it. If it doesn't, exclude it.
•This also seems like a question of how to apply a displacement and restraint at the same location. If this is the case, then apply the restraint normally. Apply a CNODE on the restraint on an otherwise unused CNODE. Apply the displacement to the element, but on the CNODE created above.

CNODE! That makes sense. Though I found that, in the latest version of CII at least, the displacement actually shows up as a restrain in the "Restraints Summary" report.

I guess using a CNODE would be the only way to give the displacement a stiffness?

Applying a restraint with a stiffness, and a displacement at that location, will result in a force equal to the displacement times stiffness in the report, plus whatever other forces are acting in the load case in question.

One problem you might face is that if you specify a displacement, the pipe will absolutely not be able to deviate from that displacement.

So if the expectation is that the cold spring will displace in the sustained case a distance "A," and then thermal growth of the pipe will combine with this to move the anchor point further to point "B," this method isn't going to work. You should just calculate the anchor force and apply it directly.

Remember: A displacement is a boundary condition. Looking at it from another viewpoint, a restraint is a zero-value displacement.