# Force: Beam

Command ElementModifies a beam element.

## Format

```
<Force_Beam
id =
```*"integer"*
i_marker_id = *"integer"*
j_marker_id = *"integer"*
length = *"real"*
E = *"real"*
G = *"real"*
area = *"real"*
ixx = *"real"*
iyy = *"real"*
izz = *"real"*
ASY = *"real"*
ASZ = *"real"*
cratio = *"real"*
preload_x = *"real"*
preload_y = *"real"*
preload_z = *"real"*
preload_tx = *"real"*
preload_ty = *"real"*
preload_tz = *"real"*
</Force_Beam>

## Attributes

`id`- Element identification number (integer>0). This number is unique among Force_Beam elements and uniquely identifies the element.
`i_marker_id`- Specifies the Reference_Marker at which the force is applied. This is designated as the point of application of the force.
`j_marker_id`- Specifies the Reference_Marker at which the reaction force and moment is
applied. This is designated as the point of reaction of the force. The
x-axis of
`j_marker_id`defines the neutral axis of the beam. The y- and z-axes should be oriented along the principal axes of the cross section (in other words, area products of inertial are zero). `length`- Specifies the free length of the beam. This is the distance from the origin of
`j_marker_id`to the origin of`i_marker_id`. `E`- Specifies the Young's modulus of the beam material. The beam is assumed to be homogeneous in its material properties. E has to be strictly positive.
`G`- Specifies the modulus of rigidity or the shear modulus of the beam. This is related to the Young's modulus and POISSON's ratio by the formula:
`area`- Specifies the area of the cross-section that is perpendicularly oriented to the neutral axis of
the beam. This is assumed to be constant along the length of the beam.
`area`is strictly positive. `ixx`- Specifies the torsional stiffness shape factor for the cross section.
`iyy`,`izz``iyy`defines the second moment of inertia of the beam cross sectional area about an axis on the cross section that is parallel to the y-axis of`j_marker_id`.`iyy`> 0.`ASY`,`ASZ``ASY`specifies the shear area ratio in the z direction for Timoshenko beams. This quantity accounts for shear deflection in the Y direction. It is calculated with the help of an integral.`cratio`- Defines the damping ratio for the beam. The beam damping matrix is calculated by multiplying the
beam stiffness matrix with the
`cratio`. In other words:- [C] = cratio * [K], where C is the damping matrix and K is the stiffness matrix.
- A value of 0.01 (or 1%) is typically used for
`cratio`. `cratio`≥ 0.

`preload_x`,`preload_y`,`preload_z`- Change the preload force in the beam in the X, Y, or Z directions.
`preload_tx`,`preload_ty`,`preload_tz`- Change the preload moment in the beam about the X, Y, or Z directions.

## Example

```
<Force_Beam
id = "307017"
length = "57.55867"
E = "200000."
G = "75000."
area = "314.1593"
ixx = "15707.96"
iyy = "7853.982"
izz = "7853.982"
ASY = "0."
ASZ = "0."
cratio = "0.01">
</Force_Beam>
```