> For the complete documentation index, see [llms.txt](https://tlcfem.gitbook.io/suanpan-manual/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://tlcfem.gitbook.io/suanpan-manual/example/structural/optimization/evolutionary-structural-optimization.md).

# evolutionary structural optimization

In this example, the optimization of a loaded panel is performed by using the BESO method. The model can be downloaded [here](https://github.com/TLCFEM/suanPan-manual/tree/dev/docs/Example/Structural/Optimization/evolutionary-structural-optimization.zip).

## Design Domain

The design domain has a dimension of $$100\times40$$ with left side fully fixed. At the center of the right side, a point load is applied. The panel is discretized with $$4000$$ `CP4` elements.

The node and elements are defined in files `node.supan` and `element.supan`. They can be loaded.

```
file node.supan
file element.supan
```

The boundary condition is applied to a group that selects all nodes on $$x=0$$.

```
generatebyrule nodegroup 1 1 1. 0.
groupmultiplierbc 1 E 1
```

## The Optimization Step

To perform structural optimization, a [`Optimization`](/suanpan-manual/step/optimization.md) step needs to be defined.

```
step Optimization 1
```

To define a proper rule to update the model by adding/deleting elements, one can use the [`StrainEnergyEvolution`](/suanpan-manual/criterion/strainenergyevolution.md) criterion. The following command defines a strain energy based evolution rule with an increment step of $$2%$$ to reach the final design level $$50%$$, that is to remove $$50%$$ elements.

```
criterion StrainEnergyEvolution 1 2 50 1 1 40
```

## Result

![optimization](https://1124082496-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FEquxr3H9WpPg4iPvT2mB%2Fuploads%2Fgit-blob-f68a8ce8ce33aaee973d43b5588847a20553ff82%2Fevolutionary-structural-optimization.gif?alt=media)


---

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