Cyclic Loading

dtopuzi · Post by **dtopuzi** » Wed Jul 08, 2009 5:12 pm

Hi,

Is it possible to apply cyclic displacements on two nodes simultaneously?

Thank You!

silvia · Post by **silvia** » Wed Jul 08, 2009 9:51 pm

yes, but i think you have to use the sp command and do load controlled analysis.
this is my guess.

dtopuzi · Post by **dtopuzi** » Thu Jul 09, 2009 7:36 am

Thank you Silvia,

That's what I have been trying actually, but for each sp, the displacement starts from zero, instead of starting from the previous displacement.

silvia · Post by **silvia** » Thu Jul 09, 2009 7:53 am

are you applying the command a few times, or are you using a load series, which is what you are supposed to use.
i have used it to apply a curvature history and have not had problems.

dtopuzi · Post by **dtopuzi** » Thu Jul 09, 2009 6:50 pm

Thank you Silvia,

I solved that in general, but in my model I experience something strange:
When I apply a load at a node, I get displacements and forces.
When I remove the load and apply an "sp" at the same node and same dof, I get no forces in the structure. (The file recording the displacements at that node is the only one without zeros).

No error messages at all...

My model is a cruciform including beamColumnJoint and nonlinearBeamColumn elements.

Thank you!

silvia · Post by **silvia** » Thu Jul 09, 2009 7:28 pm

remember, you apply a load you need to use a load-control or disp-controlled integrator (gravity or lateral).
when applying an sp, you have to use the load integrator.
if you search the forums, i had posted a script where i did a moment-curvature analysis applying an axial load and an sp.

dtopuzi · Post by **dtopuzi** » Thu Jul 09, 2009 7:47 pm

I've used LoadControl in both cases.
It also works with linear elements, but not with nonlinear ones.

I will check your example;
Thank you again!