Pipe rigidly supported indicates vertical movement down during load case, why?
Example:
Given rigidly supported node point 5470, notice that for both Gravity and Thermal load case node point moves down some distance, why?
How one should go about investigating this problem ?
1. Confirm that support stiffness was set to Rigid.
Answer: using example image above, Yes support stiffness is set to Rigid . OK
2. Check AutoPIPE's setting "Rigid Stiffness Anchors & Supports", confirm value was set sufficiently high enough to be considered rigid.
Note: Only in theory can an item be considered as infinitely rigid. Otherwise with any stiffness value, no mater how high, there may be some minimal amount of movement.
Answer: using example image above, Yes, default stiffness values were used, OK
3. Check the Pipe arrangement (i.e. is pipe slopped)
Answer: Would appear that the pipe is arrangement is horizontal on the Z axis, OK
Agree....?
Not so fast, notice that the offset units have no decimal values. let us increase the decimal value on the Edit Model Options dialog to 4.
Now let us look at the node point offsets:
There is the answer, the pipe is slopping down! Therefore, any axial movement of the pipe will also indicate vertical displacement.
IF piping was modeled on a purely horizontal / vertical axis, axial pipe movement thought a rigid support with gaps closed would only show as displacement on that one axis direction. Conversely, when pipes are sloped, axial pipe displacement could be in 2 or 3 axis directions.
Displacement report
Bentley AutoPIPE