5 Replies Latest reply on Nov 2, 2018 3:19 AM by Erik Kostson

    Rayleight damping alpha, beta value suggestion request.

    Udaya Manu

      Hello,

      I'm try to run nonlinear dynamic simulation to bellow show structure.

      The result looks abnormal. I believe the reason was wrong input of alpha, beta.

      I used alpha-0.11 beta -0.000289

      please suggest propper alpha, beta value to use with this.

      3D drawing attached here with.

       

      Force-1 = force -2

       

      Thank you.

      Udaya.

        • Re: Rayleight damping alpha, beta value suggestion request.
          Erik Kostson

          If you have the modal damping for the modes of interest, and their frequency than there is a relation between that, and the alpha and beta coefficient.

          Below is an extract from Strand7 Help, were the alpha and beta are given explicitly:

          abst7.JPG

           

           

          Further more if you assume that the two modes of interest have the same modal damping (different freq. of course), then these relations/equations become trivial and are as shown below:

          ab.JPG

          This is all explained in the solidworks help (just search for Rayleigh damping).

           

          Finally typical damping ratios values (Greek letter  z in the above equations, is modal damping ratio) for steel welded frames can be between 0.5% - 2% (0.005-0.02).