Disp vector not called in load case, but is used in analysis

HI,
I'm analysing Transportation case for a skid system already analysed for operating conditions with displacements input at Tie-in flanges.
From the same file for the transportation case, I'm building load cases as required (i.e. the combinations of directional accelerations with WNC) and for these I'm nowhere mentioning the displacement vectors in load case. From this I get a set of stress results.
Next, when I'm deleting the displacements at the tie-in points from the input model itself amd with the same set of load cases I'm getting different set of stress results.
My concern is that if the displacement vectors are not included in the load cases then how the same is being considered for the stress computation! I agree that the boundary conditions are getting changed in both the case but still, the displacement vectors are not called in.

It is difficult to determine your situation here.

If you add a new load case component (e.g., D1) to a model that was already analyzed, you must either "Recommend" Load Cases again or enter that load component by hand (e.g., change W+T1+P1 to W+T1+P1+D1) to get that load in the analysis.

Hi Dave,

Let me make it very straight forward.

When I have included displacement in the Caesar Spreadsheet but I haven't included the same (i.e. D1 vectors) while defining the load case intentionally and made a run, the report generared should be same as without any displacement fed in the input model i.e. Caesar Spreadsheet.....

Here what I feel is that when displacement vectors are not included in load cases, they shall not involved in any computation and once they are not involved in any computation, they are as good as being an idle entry in the system. But this is not the case as the result varies in both cases.

The software doesn't work that way. If you define a displacement vector (D1), any DOF that you restrain is restrained in the model - regardless of whether or not you include D1 in the load vectors.

Recognize that a displacement is a boundary condition. Consider a vessel nozzle where you define D1 as {0, .5, 0., 0., 0., 0.} In a case where you include D1 you would expect DY to be 0.5 and the other five DOF to be zero. In a case where you don't include D1 (such as W+P1, SUS) you would want all six DOF to be zero, not free.

Thanks Richard!