# F21

2D Force Based Bernoulli Beam

* Number of Nodes: 2
* Number of DoFs: 3 (Translation, Translation, Rotation)

## Syntax

```
element F21 (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.

## Output Type

This model supports the following additional history variables to be recorded.

| variable label | physical meaning          |
| -------------- | ------------------------- |
| BEAME          | local element deformation |
| BEAMS          | local element resistance  |

For example,

```
hdf5recorder (1) Element BEAME (2...)
hdf5recorder (1) Element BEAMS (2...)
# (1) int, unique recorder tag
# (2...) int, tags of elements to record
```
