Mass matrix with values equal to zero

- March 18, 2024 at 12:55 pm
  
  Murilo Granato
  Subscriber
  
  Hello.
  
  I am performing a modal analisys of a beam with two nodes restricteds in UX, UZ, ROTX, ROTY. I need to take the mass matrix of this analysis and compare with this analytical matrix:
  
  But when I extract the matrix from the analysis, I get some valeus equal to zero, which should not happen.
  Can anyone help me?
- March 19, 2024 at 4:33 pm
  
  Aurojyoti Prusty
  Ansys Employee
  
  Hi,
  Generally we get some values zero, when the dofs in that position does not have any effect on the other dof. For example, in this case, (2,1) is 0. It means there is no effect of dof=2 on dof=1. I think you have extracted this from the global mass matrix which is coming from number of beam elements. Do you mind to share, how did you get the numerical values of mass matrix ? How does your model look like?
  Thanks
  Aurojyoti.