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Superelements in finite element analysis (FEA) are pre-computed structural components that serve as efficient building blocks in larger simulations. They provide a powerful method for achieving computational efficiency and modularity in structural analysis and topology optimization. A superelement is essentially a condensed mathematical representation of a complex structural component. The key concept is that internal degrees of freedom are eliminated, while only the boundary or connection points retain their full degrees of freedom. The interior structural behavior is captured and preserved through reduced mathematical matrices.

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Practical Applications

Superelements are particularly valuable in several scenarios: Repetitive Components: When identical parts appear multiple times in an assembly—such as bolts, brackets, or standard components—you can create one superelement and reuse it throughout the model, eliminating redundant computation. Computational Efficiency: Large assemblies become significantly more manageable when complex subcomponents are replaced with their superelement equivalents. This approach dramatically reduces:
  • Solution time
  • Memory requirements
  • Model complexity
Hierarchical Analysis: Perform detailed analysis on individual components first, then use those results as superelements in system-level studies. This enables a structured approach to complex multi-scale problems.

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How to use them in nTop

nTop enables you to import existing, pre-computed stiffness and mass matrices from other analysis tools and assign them as FE domains in analysis and optimization models to streamline multi-component assembly simulations. The FE Points of the superelement define its boundaries, which can be connected to other domains using connectors or used for applying boundary conditions.

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Importing Superelements

You can import existing superelements using the Import Superelement block, which accepts the following inputs:

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Required Files

  • DMIG File: Path to a .bdf file containing the superelement’s stiffness, mass properties, and external grid IDs
  • Grid File: Path to the .fem file defining the global coordinates of the superelement’s external grid points

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Configuration

  • Unit System: Specify the unit system used for the imported superelement to ensure consistent translation of properties into your current analysis unit system

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Download the Example file:

Example File