Random vibrations simulation

Hello

I am new to this forum. I have a question for you.


I am trying to simulate a problem in which there are multiple random input sources.

I know how to solve the problem when there are only two sources(correlated or uncorrelated). Can anybody tell me how one should formulate a problem if I have multiple (say 4) random inputs(correlated or uncorrelated).

I am specifically interested in the matrix of input excitations(for say, S11 as psd of source one,S22 of 2.....etc and S12 is the cross PSD of sources 1&2, S13 of 1& 3 etc)

I am going to be using NASTRAN for the solution.



Rahul