How do I model a clevis hanger (Anvil Fig. 260) on a rod (z direction) that allows axial translation (along y direction), but forces the pipe to rotate about the rod (in x direction)?

Assuming that vertical up is +Z, you may model as +ZROD with proper length.

Regards,

That models it as a typical rod and will rotate around the 'x' axis. I need to allow translation in the 'y' direction. The 'x' axis of the rod will move along the 'y' axis, so rotation occurs only around the 'y' axis.

Why are you assuming that the rotation will occur around 'y' axis only? If you have a +ZROD defined, the program will allow rotation in the other two directions by default, unless they are restrained.

If my understanding is not correct, please send in a sketch to clarify.

Regards,

See the attached hanger detail.
I want to allow the translation from the roller while keeping the rotation from the rod. This is for a seismic analysis of an existing system.

If you need to allow the translation, then you may model as +Y without friction. This is because you will have to brace about every three supports (pending on diameter) so it will not rotate very much. In any case rotation is limited to 4 degrees normaly.

See the attached file that shows the input settings that will model it properly.

The cnode(41) restraint in the axial 'y' direction that has a cnode back to the restraint node(40) was key to making it work. It would not converge otherwise.

Your model shows that you rod is free to move on Y direction. It may work at some degree. I think that you may also delete 41 CN 40 Y

sdeloe

I disagree with what you stated and am not very convinced. Why? I made a test run myself using a simple model. Your approach did not make any real difference to the results. The displacements and loads did not change a single bit from one case to the other (please see the attached file and note that my Y-axis is your Z-axis). The only difference when having the pair of 7 CN 70 and 70 CN 7 Z is that 70 (point in space) follows the Z displacement of 7. How does that change the results of the analysis? I do not understand what exactly it is you want to model and why?

What danb stated is probably what you want to do to model the frictionless translation of the pipe.

I am interested to understand your concern. Please think it through and revert back with a clearer description of your concern.

Thanks,

sdeloe

I figured out something that might be useful for you. The clevis-type support that you sent in the sketch for is more similar to a rod-hanger in that it does not act in the -Y direction. At the same time, it is not a pure +Y resting-type support because it's range of motion follows a parabolic path (which is the reason why the X/Y/ZROD type of support was introduced into CAESAR).

Therefore, my personal idea of how to model this type of support (as well as a rod-hanger for that matter too) and combine the two effects mentioned above is as follows:
1. Define a +ZROD @ 40 with a CNODE @ 41
2. Define a +Z (with no friction coefficient) @ 41

I have also attached a snapshot of the input screen for clarification.

If you have something else in mind, please send it in.
Regards,

Run the analysis with a significant displacement of 4" X direction and 6" in Y direction, and you will see a difference. The displacements you used in the test are insignificant.