Snubber Modelling Query
In cases where the snubber support is attached to the external structural support, we provide the Cnode with the displacements and the snubber restraint locations.
However, when the snubber is supported off another vessel example Column-Reboiler, it gets complicated.
Looking at one of the system which has been modelled with a Rigid element from the column centreline to the outside edge of the column where one end of snubber is
Attached. The other end is attached to the re-boiler, with the intention of transferring the re-boiler seismic loads to the Column.

The issue is the thermal displacement of the re-boiler side is different from the thermal displacement at the column side. In conventional snubber design the displacements at
The snubber location in the restraint output would match the displacements at the operating case where the snubber is not active. But this is not the case with cnoding to the
Actual column connection.

If we change the system and define the reboiler side displacement at the snubber location and ignore the connection to the column that may not be accurate as the thermal
Displacements at the column end (which is higher) is not captured.
Anyone encountered a similar situation ?

Am I correct in assuming that your model has nonlinear conditions?

If your system is linear, you can separate your operating analysis from your transient event. The operating case can have the snubber inactive in the operating case and active in the transient case. A check box in the load case editor provides this switch.

But things get more complicated if you have a nonlinear model and wish to build a single load case to represent the transient event while the system is in operation. And, yes, when not modeling the equipment on the other end of that snubber, the model trick is to include operating displacements on that CNode which locates the snubber in the operating position.

Here's another (untested) trick: Use a cut element (material #18 or #19) to strain the CNode to the proper operating position for this transient analysis. I would put it in with the rigid element from the vessel centerline to wall. The load case for operating plus transient would be the only load case than includes this "CS" load component. If you give this a try, CHECK YOUR RESULTS,, closely.

Let us know what happens...

Dave
Thanks for your response. To explain better my question, I have attached a sketch of the system. The displacements at the nodes 50 and 500 in the sketch are not the same. c-noding the snubber at node 500 to 50 is not producing expected results.
And finding the cut-short length to match the displacements maybe iterative. I shall try it anyway and let you know..

any updates on this topic?
I think, displacement should be same at those nodes