Modal Analysis

Click the Tools menu > Job Preferences > Structure Analysis > Modal Analysis to open the Modal Analysis dialog.

You can select the following modal analysis parameters:

• Coefficient of Participation:

  Sum of absolute values - the participation coefficient is calculated during dynamic calculations as the sum of absolute values of coefficients for each direction.

  Square root of a sum of squares - the participation coefficient is calculated during dynamic calculations as the square root of a sum of squares for each direction.

• Mass Matrix Type:

  Consistent - a matrix always with rotational degrees of freedom.

  Lumped with Rotations - a diagonal matrix lumped with rotational degrees of freedom.

  Lumped without Rotations - a diagonal matrix lumped without rotational degrees of freedom.

• Method of eigenproblem solution :

  Subspace Iteration - this method is used in the eigenproblem solution.

  Lanczos' Method - this method is used in the eigenproblem algorithm. This means that the first "n" eigenvalues and eigenvectors can be found with any tolerance. This method is based on the reduced eigenproblem set of equations with Lanczos' vectors.

Note: You cannot use Lanczos' method for structures that are separated (Lanczos' method requires a lumped T tridiagonal matrix, while a separated structure - a consistent T matrix). To use Lanczos' method, you must connect structures that are separated in such as way as not to change the structure model. For example, you can add a bar among the supports. If Lanczos' method is selected, calculations are performed using the subspace iteration method.