Hi all,
I am modelling a vertical pipe guided from a vessel at a node (1010 on the pipe) and Cnode from node 30 from the vessel. From the same node 30, two spring hangers carry the same pipe from a lower node (1020) as attached in the photos.

I have tried to put a guide at node 1010 with Cnode 30 and define spring at node 1020 with Cnode 30 but an intersection coordinate mismatch error occurred.
My suggestion is to define spring at node 1020 with Cnode 31 (Virtual node) and define a (-YROD) Restrained at node 31 with Cnode to the vessel support 30.
Would that be correct? Any better suggestion is highly appreciated.

Thanks in advance.
Best regards
MAGA

Hi Maga,
One simplified approach is to model rigid element from node 10 to 1020. define cnode and connect with spring. vertical rigid element should be at ambient tempterature as support growth will be calculated with base connection at node 10.

Another way to define cnode at node 1010/1020 and provide corresponding vessel thermal growth in displacement tab.

Hi Naren,
Thanks for your idea to add a rigid element with ambient temperature. Whats is your thoughts about the following
- Added Rigid no weight from 31 to 40 (31 is restrained in X,Y,Z Conde 30), and
- Put the spring in the 1020 Code to 40.

I guess that would consider the lateral displacement of the vessel, add the swing effect of the spring hanger.

Do you think that would model this support in a more accurate way?

Cheers,
MAGA

Hi Maga,
In this case you need to fix all DOF including rotation RX, RY, RZ and define zero relative dispalcement at node 30/31. This approach i am not sure what added advantage you will get.

Hi Naren,
I was thinking to restrain the X, Y, Z movements for the 30/31 and similarly at the connection with the spring and leave the rotational movements unrestrained. The point is the guide at 1010 has a gap and I need to take the swing effect created by the spring hanger in consideration. Do you think that would enhance the system accuracy?

Cheers,
MAGA

Spring horizontal movement you can get from the output results and verify if spring swing is within 4deg. Its an output basically not an input in your case.
secondly what I advised above to fix all DOF the spring top (Node30) which will be pivot point to check spring displacement at node 1020. there is no relative dispalcement at the top which is common location for your guide and spring assembly weld-on eye plate connection.

The Guide GAP with pipe has nothing to do with sping eye plate connection, its a fix connection assuming your spring eye plate will be welded to same vessel cleat. once it is welded it has no relative displacement and will move same as cleat movemement due to different locading scenarios you have created load cases for. Due to guide gap, pipe horizontal movement can be seen at node 1020 in output summary.

My advise is to follwo simple rigid element methodology which i mention above and keep your model simple if you are not aiming for something else.

Well, I guess restraining rotations, RX, RY, RZ between node 30/31 will not make much difference as 1020 is connected to node 40 with C node hanger; hence effects of X, Z movement of 1020 shall not be transferred to node 40 and subsequently 30. You may try in model and tell if results are different.

I shall also suggest weightless rigid element at ambient temperature as suggested by Naren. You may, however model dummy pipe on which hanger shall be mounted for more accurate results. Also the support configuration drawn by you is a very common vessel clip support arrangement and by experience, I do not envisage any problems of angularity in the hanger due to lateral expansion of the column or axial expansion of trunioun. You may reconfirm by manually checking if tan-1(|horizontal disp of spring node (1020) - horizontal disp of spring pivot pt (30)|/height of hanger) is within 4 deg.

Thanks Naren and Kushal for your help and suggestions, I will test the two options and check if there is any difference in the results if I added the angular flexibility.
Cheers,
MAGA