How to use reaction forces in a secondary analysis

Objective:

Learn how to use the reaction forces from a previous analysis to run a secondary analysis.

Applies to:

  • Simulation
  • Static Analysis
  • nTop 3.26+

Procedure:

Note: We are updating our quadratic nodes in 3.26, so we don't recommend using quadratic nodes to get your reaction forces. Use a Linear Geometric order to get the results. Then do the actual evaluation with Quadratic Geometric order to get more accuracy.

Start with a completed static analysis.

We can extract the reaction forces from the Static Analysis block Properties panel. The reaction forces property is a Vector Field type, but we want to create a Vector to use in a Force block for our secondary analysis. 

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1. Extract the X, Y, and Z components from the 'reaction force' property chip and add them to the Notebook. Rename them so you know which direction each chip belongs.

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2. We want to evaluate each of these fields at the nodes they are acting upon. These nodes are found in the Displacement Restraint block Properties panel.

    • Expand the 'boundary' chip and drag the 'nodes (230)' chip into the Notebook. Rename the chip to "reaction nodes"

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3. Once we have the nodes, add an Evaluate Field block for each direction. 

    • Set the inputs to:
      • Scalar field: reaction force x, reaction force y, and reaction force z from step 1.
      • Point: reaction nodes from step 2.

4. Each block has 230 values. We want to add these values together to get the reaction force in each direction. 

    • Use an Add block to sum the values together. The result is shown in the right-hand corner of the block (and also in the properties).

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5. Use the three values to create a Vector.

    • Add a Vector block.
      • Insert the blocks from the previous step into their respective X, Y, and Z inputs.

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6. Build a Force block.

    • Add a Force block.
      • Use the Boundary from the Displacement Restraint in the Boundary input.
      • Use the Vector from the previous step in the Vector input.

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And that’s it! You’ve successfully used reaction forces as a boundary condition

Are you still having issues? Contact the support team, and we’ll be happy to help!

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Keywords:

 analysis simulation boundary force condition vector how-to reaction resultant forces 
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