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CNTNLSUB - Load decreases in second step

Hello,

I'm conducting a nonlinear static analysis involving two load cases. In the first case, I applied a vertical load, and after completing the simulation, I applied a horizontal load. I utilized "CNTNLSUB." When plotting the reaction for the entire simulation, I observed that the vertical load in the second step gradually decreased, which was contrary to my intention. Any suggestions on how to maintain the load contact during the second simulation run?

Thanks.

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OptiStruct

v2023.1

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Adriano_Koga

Hi,

If you wish to keep the vertical load as well, besides using CNTNLSUB, you need to keep the vertical force in addition to the new horizontal load. You will need to duplicate the vertical load into the new loadcase, or you could create a LOADADD entity, which allows you to combine 2 or more loads into the same loadcase.

In your case you've probably removed the vertical force form the second load case.

Faroque

Hi,
If you wish to keep the vertical load as well, besides using CNTNLSUB, you need to keep the vertical force in addition to the new horizontal load. You will need to duplicate the vertical load into the new loadcase, or you could create a LOADADD entity, which allows you to combine 2 or more loads into the same loadcase.
In your case you've probably removed the vertical force form the second load case.

Thanks for your advice. I'm wondering why I have to load twice when using the CNTNLSUB option, or add two cases with LOADADD. It is a common practice to have multiple stages of loading. Also, I'm struggling to understand what "CNTNLSUB" means physically.

I've also tried using a load curve option like this:

I defined a curve totaling 2 seconds; 0 to 1 is a ramp, and 1 to 2 seconds is a constant value, but Optistruct did not follow the curve.