hello

I am working with modeling software CAESAR II, a pipeline mounted on a mobile rack (movement of the earthquake) I want to model a support mounted on a rack with a displacement (X = +-30mm, Y = +-50mm ,Z (vertical) = 0mm).
is that true to make as the following?:
support node 40 (with Z + restarint CNOD 2040) and the three displacement vectors V1 (Dx = 30, remains free (empty)
V2 (Dy = 50, remains free
V3 (Dz = 0, remains free

thank you for advance

If the X and Y displacements occur simultaneously then you want this:

Vector 1:
DX = 30
DY = 50
DZ = 0
RX -> RZ free

If the displacements occur independently, then yes you would need Vectors 1 and 2 as stated above.

THANK YOU Mr Richard


WHAT ABOUT VECTOR V3 (DZ=0) will introduced or not???




thank you for advance

Yes you could use vector 3, with DZ=0.

My opinion is that since the Cnode belong to the rack it should not have free rotations and/or translations but 0. Correct me if I'm wrong.

Regards,

Dear all,

when the three {many} displacement is not occur simultaneously. then we have three {many} displacement vectors.

the problem here that the CII make fixation in cell remain empety and this is according to the following note in CII help:

"If an imposed displacement is specified for a specific degree-of-freedom, that degree-of-freedom will be considered restrained for all load cases whether or not they contain that displacement set."

how can forced the system to treat all empety cells as free????????

best regards

You can't, because that makes no sense. Consider what you're modeling physically - what is that connection? How could you have a connection that displaces (restricts) a particular DOF in one condition, but allows that same DOF to be free in another condition?

For example, consider a U-bolt which provides restraint in Y and Z (assume the pipe is running in X. Now if this location is displaced in Y and Z this could be defined as:

DX = blank, free
DY = dy
DZ = dz
RX = blank, free
RY = blank, free
RZ = blank, free

Now, if the displacements were considered separately:

DX1 = blank, free
DY1 = dy
DZ1 = blank , NOT FREE because DZ2 is specified
RX1 = blank, free
RY1 = blank, free
RZ1 = blank, free

DX2 = blank, free
DY2 = blank, NOT FREE because DY1 is specified
DZ2 = dz
RX2 = blank, free
RY2 = blank, free
RZ2 = blank, free

Think about it, you still have the U-bolt, even if you only displace it in DY, the DZ DOF is still not free.

The same discussion can be applied to a nozzle - all 6 DOFs are restrained. You can't have a DOF restrained/displaced in one condition and free in another.

But if you really want to do it you would have to enter each as a separate analysis.

I still think that the correct way is to insert zero for the DOF that do not have displacements and not to let them free.
If, for example you leave dx free you will miss the friction on this direction. (see attached)

Regards,

Dear all,

Thanks for your help.

BEST REGARDS