Evaluating the Results

You can control in the Navigator - Results what results are displayed on the model. By default, the mode shapes |u| of the first normal mode are set (see the Mode Shape of Lowest Natural Frequency image).

Natural Frequencies

The No. | Natural Frequency f [Hz] list includes all 33 modes that are required to exceed the limit sums of 90% for the factors of modal masses. By clicking the and buttons next to the list, you can browse through the natural frequencies of the model. You can also select a specific mode directly when opening the list.

Mode Shape Related to Seventh Natural Frequency

Click on the button on the toolbar to display the mode shapes as an animated representation.

Displaying Mode Shape as Animation

Press the button again to stop the animation.

Mode Shapes

Every frequency of the model has a corresponding mode shape. Though those mode shape vectors have the appearance of the deformations resulting from a structural analysis, they do not represent "deformations" in the actual sense. Rather, the displacements and rotations are scaled to the maximum value of 1 and are dimensionless. They are thus referred to as 'Normalized Displacements' and 'Normalized Rotations' in the table headings (see the Normalized Mode Shape Results by Node image).

You can display every translational and rotational shape component by selecting one of the options in the 'Mode Shape' category of the navigator. Select the u_Z component, for example.

Displaying uZ Mode Shape Component

When you have tried out some of the other options, set the scaled |u| results again. If you want to scale the maximum results to a different maximum, you can apply one of the specific options available in the bottom part of the navigator. They are explained in the Online Manual.

Scaling Options for Mode Shapes

Effective Modal Masses

As you have already noticed, the Effective Modal Masses table provides important information when deciding on the number of required modes (see the Factors for Effective Modal Masses image). The effective modal masses describe how much mass is activated in each direction by each natural frequency.

Masses in Mesh Points

You can check the masses that were taken into account for the modal analysis. To do so, select the Masses in Mesh Points table.

Checking Masses in Mesh Points

The masses result from the loads contained in the Load Combination CO9 . They are only effective in the X and Y directions as specified in the Modal Analysis Settings . At the very end of the table, the sums for each direction are displayed.

To display the masses graphically on the FE nodes of the model, select the Masses check box in the 'Navigator - Results'. The masses m_X acting in the X direction are set by default.

Masses in Mesh Points Acting in X Direction

The mass applied to each mesh node is represented by a ball whose size is scaled to the maximum value. Again, only the m_X and m_Y options are relevant. The members have no mass balls as their masses were not taken into account for the modal analysis (see the Neglecting Masses of Specific Members image).

Numerical Results of Mode Shapes

The values of all mode shapes are sorted in corresponding tables. You can select them from the subcategories available for the 'Modal Analysis'.

Normalized Mode Shape Results by Node

The normalized displacements and rotations of the nodes, members or surfaces are listed by object number or mode shape.

Finally, save the modal analysis results by clicking the button on the toolbar.