Body forces are static loads that include added masses.
This type of load generates forces resulting from a mass of elements and masses added in nodes or elements for a given acceleration. The value of the generated force is: F = m * a.
The acceleration is defined by specifying values for 3 components in the global coordinate system X, Y, and Z. You can define an acceleration vector in any direction. In particular, for the acceleration of the vector (0,0,-g), a load value identical to self-weight is generated.
To easily define the acceleration in relation to the acceleration of gravity g, you can specify a factor determining the ratio of the acceleration to the acceleration of gravity a/g. If the Relative x g option is selected, the specified value is non-dimensional and treated as a value of the a/g factor. It is assumed that the orientation of the generated force is identical to the orientation of the acceleration vector.
This type of load can be used to define imposed displacements with structure acceleration during transport or to generate a self-weight load in any direction during structure storage.