Transient Modal Dynamic with Displacement Base Motion - Optistruct

Jeganathan

Hi,

I'm simulating a sample model for modal transient dynamic analysis with displacement history as base motion. But the behavior seems like, the effect of gravity is not considered into the simulation. At any given instant of time, only the geometrical stiffness of structure plays the role but not the mass effect.

How to include the mass effect into the transient analysis with displacement base motion?

I have attached the .fem file for reference.

Thanks.

Transient_Example_BlockMass.fem

solon

Hello,

You can refer to the bellow discussion:

In the Modal Transient you can add STATSUB(PRELOAD)=ID of Static subcase with gravity.

https://community.altair.com/discussion/21800/how-to-include-both-gravity-and-multi-point-time-domain-dynamic-loads-in-a-loadstep

Jeganathan

Hi Solon,

I tried by adding gravity subcase as preload for the transient modal dynamic step.

But i didn't find any change in the behavior.

Could you please once check it?

I've attached the .fem file for your reference.

Thanks.

Transient_Example_BlockMass_PreLoad.fem

solon

STATSUB(PRELOAD) will only include the effects of preloading as a weakening or a stiffening of the structure and will not transfer the stresses, displacements.

To add the two load steps, you can either do it in post-processing with Hyperview, or more easily, you can create a TLOAD1 card for the gravity load with a constant TABLED1 in the transient analysis. Then, simply include the TLOAD1 card in the DLOAD entry along with your other loads. See model attached:

Transient_Example_BlockMas_dload.fem

Jeganathan

Hi Solon,

Got it! Many thanks for the quick help & support.