Altair RISE

A program to recognize and reward our most engaged community members

Nominate Yourself Now!

Random Response Analysis using two sets of PSDs

Hello everyone,

I want to apply two sets of PSD to two nodes of the model.

For example, PSD1 table is applied to node1, and PSD2 table is applied to node2.

I don't understand in the RANDPS load collector what are the J and K input. It is said in the User Guide that there is a excited load and an applied load? How can they be different, what does that mean?

Thank you for your help.

Hiroshi

Find more posts tagged with

English

OptiStruct

Accepted answers

All comments

Adriano_Koga

Maybe this post might help you.

https://community.altair.com/community?id=community_question&sys_id=d64600b61b2bd0908017dc61ec4bcb9d&view_source=searchResult

You will use different J and K when you need to input the Cross-PSDs in your model.

Hiroshi Aoyama

Thank you very much!!!

"You will use different J and K when you need to input the Cross-PSDs in your model."

This is the answer what I need.

PedroCarneiro

Dear @Adriano_Koga i am currently working on the topic of random response analysis and i came across this post and i would like to put some questions regarding the definition of the RANDPS. When i have only one PSD curve which corresponds to only one load, i need equally to defined the J and K but i need to insert the same load on both. Is this correct? In this case why we need to define the J and K to the same value instead of define only one? i am a little bit confuse on this and i will appreciate your help.

Adriano_Koga

if you're supplying a single base excitation, with a single PSD, then J = K.

Now if you have different base excitations, you might need to compute Cross-PSDs and supply them using J and K, for each of them.

PedroCarneiro

Thanks for the answer. For example, in the OS-T 1325 Random Response Analysis of a flat plate, when combining the two loads in J and K, the inputs given are Load Step Load1 and Load2, which correspond to the direct frequency response of the two distinct loads. The PSD curve applied is the same and it is only one, correct? In the case where only one load is present, it is necessary to enter the load step of the direct or modal frequency response of the defined unique load in both J and K, correct?