Modal Analysis - Bridge

Use modal analysis to calculate the first 3 flexible modes of a bridge assembly.


SimSolid performs meshless structural analysis that works on full featured parts and assemblies, is tolerant of geometric imperfections, and runs in seconds to minutes. In this tutorial, you will do the following:
  • Learn the SimSolid workflow.
  • Create modal analysis to calculate flexible modes.

Model Description

The model used in this tutorial is a 30-part bridge assembly.

The following model file is needed for this tutorial:
  • bridge.stl
  • bridge.ssp

Import Geometry

Import model geometry into SimSolid.

  1. Open a new SimSolid session.
  2. Click the (Import from file) icon.

    Figure 1.
  3. In the Open geometry files dialog, choose bridge.stl.
  4. Click Open.
    The assembly will load in the modeling window.
  5. In the Length units dialog, select the inch [in] radio button.

Create Connections

Specify gap and penetration tolerances to create automatic connections.

  1. In the Project Tree, click on the Connections branch.
  2. In the Connections workbench toolbar, click (Automatic connections).
  3. Specify Gap and Penetration tolerances as 0.1.
  4. Set Connection resolution level to Increased.
  5. Click OK.
    • SimSolid will create connections even in areas with overlapping geometry.
    • SimSolid will automatically identify bolts, nuts and washers.
    • Sliding contact will be applied automatically in bolt shanks, bonded otherwise.

Assign Materials

Apply materials to all parts in the assembly.

  1. In the Project Tree, click on the Assembly branch.
  2. In the Assembly workbench, click (Apply materials).
  3. Pick Steel from the Generic materials list.
  4. Click Apply to all parts.
  5. Click Close.
    In the Assembly branch of the Project Tree, material properties are identified for each part.

Create Modal Analysis

  1. On the main window toolbar, click the (Modal analysis) icon.

    Figure 2.
  2. In the popup Number of modes window, specify the number of modes as 9.
  3. Click OK.
    The new modal analysis will appear in the Project Tree.

Run Analysis

Solve the analysis.

  1. In the Project Tree, open the Analysis Workbench.
  2. Click (Solve).

Calculate Flexible Modes

Calculate the first three flexible modes.

  1. Plot the Displacement magnitude contour.
    1. On the Analysis workbench toolbar, click the (Results plot) icon.
    2. In the menu, select Displacement magnitude.
    The Lengend window will appear showing the contour plot. A Frequency window will also open.
  2. Calculate the first three flexible modes.
    1. In the Frequency [Hz] window, select the seventh frequency in the list.
    2. In the Legend window, pick the (Show deformed shape) icon.
    3. Click the button to animate the mode shape.
  3. Repeat step 2 for the eighth and ninth frequencies.