Hi Friends,

I have observed in one of my CII models the Anchor stiffness tied to a CNODE with forced thermal displacement = -0.177 N/mm from modal analysis. CII Default Translation stiffness = 1.7512 E11 N/mm while rotational stiffness = 1.13 E11 N/mm. I expected the same stiffness to be attached to my translation and rotational dof's at Anchor support location.

Also, to be noted is the fact that if we model individual restraints say a Rigid Y with CNODE having Dy movement the stiffness = 1.7512 E11 N/mm as per the default value.

Only for Anchor support with CNODE having forced thermal displacements in X,Y,Z this problem has come.

Request you to suggest as to how we could rectify this problem.

Thanks in advance

Full anchor should have all 6 dofs defined. Did you leave rx, ry, rz displacements blank?

Hello Ranka,

No, I had defined the restraint node as an Anchor with CNODE. Data for all 6 degrees of freedom have been specified. At the CNODE I defined displacements in X,Y,Z and Rotations were arrested i.e. 0 value was specified.

I would also point the fact that even if I did not define CNODE the default anchor stiffness taken by Caesar II is -0.177 N/mm. You could check this effect if you run modal analysis of a simple cantilever Beam model, the active bcs would show Anchor restraint stiffness as -0.177 N/mm.

Regards

Benoy

Hi Benoy
I do not understand why you are getting low stiffness.
In test with simple cantilever: one end ancored, other end anc with cnode displacement - modal analysis boundary condition report shows "rigid"

Hi Ranka,

I am not sure if you have referred to Dynamic Boundary condition Report. For the example i tried the output is as below-

DYNAMIC BOUNDARY CONDITION REPORT


-------Cosines-------- (N./mm. )
NODE X Y Z STIFFNESS DESCRIPTION

10 0.000 0.000 0.000 -1.768887e-001 Rigid ANC
50 0.000 0.000 0.000 -1.768887e-001 Rigid ANC
51 1.000 1.000 1.000 -1.768887e-001 Displ. Reaction

Please have a look and let me know.

Regards

Benoy

No, my results are:
10 0.000 0.000 0.000 RIGID Rigid ANC
30 0.000 0.000 0.000 RIGID Rigid ANC
31 1.000 1.000 1.000 RIGID Displ. Reaction

Hi Ranka,

There seems to be some difference in CII version which we are using. We are using Version 5.2. We get the stiffness value at each support location.

Is there some internal adjustment in Restraint stiffness done by CII. CNode is tied to Anchor and CNODE will be able to move the support by the displacements specified only if CNODE stiffness is atleast equal to, if not greater than that of the Anchor support.

Regards

Benoy

Benoy,

There have been no changes across any CAESAR II version that would alter your stiffnesses in this fashion. Open a Support Request on eCustomer and submit your job file for review.