> 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/element/beam/b21.md).

# B21

2D Displacement Based Bernoulli Beam

* Number of Nodes: 2
* Number of DoFs: 3 (Translation, Translation, Rotation)
* DoF Label: U1, U2, UR3

## Syntax

```
element B21 (1) (2) (3) (4) [5] [6]
# (1) int, unique element tag
# (2) int, node i
# (3) int, node j
# (4) int, section tag
# [5] int, number of integration points, default: 6
# [6] bool string, nonlinear geometry switch, default: false
```

## Remarks

1. The Lobatto integration is used by default. The number of integration points ranges from 3 to 20.
2. To use the corotational formulation for nonlinearity, please turn on the switch.
3. Unlike 3D beam elements, there is no need to attach an `orientation` to 2D beam elements.


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