Display Bolt/Nut Resultant Forces

Displays a table of resultant bolt and nut forces

This tool is supported for both structural static and dynamic analysis.

Important: To access this tool, an analysis must be solved first.

Structural Static Analysis

  1. In the Project Tree, click on a Structural analysis branch to open the Analysis workbench.
  2. In the Analysis Workbench, select Fastener resultant forces > Bolt/nut resultant forces.
    The Bolt/nut forces dialog will open and display a table of resultant forces for tightened or not tightened bolts and nuts.
  3. Go to the desired tab to display either Bolts or Nuts.
    Note: If there are no bolts and/or nuts in the model, the respective tab(s) will not be available.
  4. Select any column header to sort the table by that header.
    Tip: Number of nut turns is also listed in the forces summary for bolts tightened via torque and axial force.
  5. Select any row to display a forces summary.
    Note: When the resultant axial force of the bolt/nut deviates by over 10%, the following occurs:
    • In the Project Tree, a warning icon appears next to the Results branch. Right-click on Results and select Warnings from the context menu.
      Figure 1.
    • In the Bolt/Nut forces dialog, nuts with significant deviation are marked in red and deviation from the target is listed.
      Figure 2.


Dynamic Analysis

Bolt/nut resultant forces can also be plotted for dynamic analysis, including transient, frequency, and random response analysis.
  1. In the Project Tree, click on a Multi-loadcases analysis branch to open the Analysis workbench.
  2. In the Analysis Workbench, select Fastener resultant forces.
    The Bolt/nut forces dialog will open and display a table of resultant forces for tightened or not tightened bolts and nuts.
  3. Go to the desired tab to display either Bolts or Nuts.
    Note: If there are no bolts and/or nuts in the model, the respective tab(s) will not be available.
  4. Select a Force/Moment type from the Response dropdown.
  5. Optional: If plotting multiple forces, select the Show each plot in separate window checkbox to create multiple plots.
  6. Click Evaluate.
    A new dialog will open showing a graph of the chosen force. Use the radio buttons in this dialog to change the axis scale.
  7. To plot the partial response, do the following.
    1. From the plot dialog, pick a point on the curve to show the Modes contributions into response table.
    2. In the table, select rows to choose which modes to include in the partial response.
    3. Click Evaluate response.
      The plot in the dialog will update to show the partial response.
Note: In the Fastener resultant forces dialog for a random response solution, choose between PSD and RMS as the response type. This selection impacts the values displayed in the table. However, when the forces are plotted, the curve will, by default, show both the RMS and PSD curves for the selected forces in a single plot.

Evaluated Forces

Description of which bolt/nut forces are evaluated

Bolts

For bolts, the following forces are evaluated in the cross-section at the base of the bolt head in location #1:
  • Axial force
  • Shearing force
  • Bending movement
as well as the corresponding nuts at location #2:
  • Axial force
  • Thread shear force
  • Bending movement (about centroid of bolt threads.
Figure 3.


For blind bolts, the second group of forces are evaluated in the centroid of the threads at the bottom of the bolt.

Nuts

In nut tightening (where a corresponding bolt is not present), the following forces are evaluated in the nut threads:
  • Thread shear force
  • Bending movement (about centroid of bolt threads)

Thread shear force is the total force that acts on the nut threads along nut axis. This force defines the main failure mode of threads through shear and can be used for threads sizing. In particular case of a bolt which can freely slide in the placement holes and is tightened by a nut, the force will be same as axial force on the bolt.