Dynamic Implicit Time history Analysis 1

[s_saranya]

I am doing a dynamic implicit time history analysis of a building in ABAQUS. I have fixed the bottom supports. I am getting this error when running the analysis "ErrNodeBCRedundantDof. How it can be rectified?. Whether the support should be released in the particular direction? Pleas suggest the solutions.

 

[FEA way]

Avoid defining multiple boundary conditions acting at the same time in the same directions for the same nodes. There might be duplicated/redundant BCs in your model.

 

[s_saranya]

The columns are fixed at the bottom. So when the ground motion is applied along the u1 direction, the following error is shown "16 nodes have dof on which velocity/displacement/acceleration/base motion etc. constraints are specified simultaneously. The nodes have been identified in node set ErrNodeBCRedundantDof." This means I have to release the constraint along u1 direction? .If I do like that the whole structure is moving along u1 direction. Is this right?

 

[FEA way]

Yes, you have to release that DOF. To achieve what you want you could use base motion boundary condition but you would have to switch to transient modal dynamic analysis (base motion is not supported in implicit dynamic step).

 

[s_saranya]

Thank you. That means the constraint along the ground motion direction should be released? To determine the displacement at the top floor , the relative displacement with respect to ground floor should be taken?

 

[FEA way]

Yes, if you want to simulate it without base motion available in linear dynamics analysis then you have to change that constraint to non-zero displacement.