Verification of BeamDyn for pure bending problems

[Min.Li]

Dear everyone,

I am verifying BeamDyn’s accuracy by simulating a cantilever beam’s pure bending, but the results are wrong. Did anyone else have the same problem?

Here is my case setup, references, and results.
case setup

references
https://www.nrel.gov/docs/fy15osti/63165.pdf

result

Even when I use BeamDyn to test small deformations of a cantilever beam, applying a distributed load or a concentrated force at the end also causes similar issues, resulting in strange curvatures. For example, the test results with a distributed load show the following figure.

The simulation’s boundary conditions might not be fixed-free. I only found the BD_BoundaryGA2 subroutine in the code related to boundary conditions, which sets the root’s velocity, displacement, and acceleration. Shouldn’t constraints be applied in the global stiffness matrix?

Where in the code are the boundary conditions set? Are they fixed-free?

If the boundary conditions aren’t the issue, what else could it be? Do you have any suggestions?

Many thanks in advance for any help.

Best regards,

[Jason.Jonkman]

Dear @Min.Li,

The BeamDyn driver assumes fixed-free boundary conditions.

I don’t see this exact test in the paper you reference; did you cite the correct paper?

I do see that your beam has some twist at the tip (initial_twist); is this correct? Perhaps that twist is explaining why your results differ from what you expect.

Best regards