Dear All,

I need to analyze a piping system which has fallen down from its shoe at almost 10 locations, within two changes in direction and between two limit stops.

I fed the displacements as per Site measurement at all the affected support points with the method discussed in CAESAR help Guide.

Re-stating the procedure : At all the affected support location nodes, I created independent Cnodes and then fed the displacement in these Cnodes as per site measurement.

There is a bit confusion regarding the results in the restraint summary(particularly for WNC+D1 case).

In the WNC+D1 case, the case in which the site measurements have been performed, I shall be getting the almost the same displacement at the support point as manually fed in the Cnode. But its not the same. For example, if the manual displacement fed is 200 mm vertical down, the support point is showing the displacement -135 mm down.

Moreover, in case of axial movements the variation in displacements is even more. For example, if the manual displacement fed is 300 mm in +X, the support point is showing the displacement +26 mm in X.

I understand that CNODES allows to associate certain degrees of freedom between two nodes, with an optional stiffness value and it is also possible that CNODE connected node won't move down the entire 200 mm, due to the pipe stiffness and associated loads, but what bothers me much is that in WNC case at least, it shall be close to the defined displacements.

If you want Tech Support to review your model and input, please open a Support Request on Smart Support (and attach the job file with relevant information).

Your CNode displacements only work if your restraint (with the CNode) is active in the direction of the displacement. E.g., A CNode's X displacement for a Y restraint will not be considered (if no friction is included).

Thanks for the quick response Richard and Dave!

The displacements are behaving in exactly the same manner as you said Dave. Its only when I specify X displacement with Cnode in X restraint I get the proper value, but there arise another problem.

The other problem is that, for a STRAIGHT run pipe, if i have defined the displacement (say 300mm in +X) at any one particular node, CAESAR II takes that displacement and propagates the same throughout that straight run. If i have some other displacement values in between (Say 225mm in +X), CAESAR II doesn't takes it into account. Stiffness remains same, frictions are deleted and displacements/restraint summary are looked into WNC case.

Cannot be two separate displacements be provided in a straight run of pipe?

If you wish to place the pipe in a certain X positions, +X may not work throughout, use X instead.