Description: In Abaqus/CAE you can now define base motion boundary conditions for modal superposition analyses. Two types of boundary conditions are available: base motion and secondary base.

You can create a boundary condition to specify the base motion of nodes in a modal dynamic step, steady-state dynamic (mode-based or subspace-based) step, or random response step. The base motion can be acceleration, velocity, or displacement. You can create a secondary base motion boundary condition in a frequency extraction step.

The new PSD definition amplitude type allows you to define a frequency function that defines the frequency dependence of the random loading in a random response analysis step. This amplitude curve represents the power spectral density function for the random noise source. The PSD amplitude can be referenced in the correlation definition of a base motion boundary condition in a random response step.

Load module:
    Create Boundary Condition; Step: step; Category: Mechanical; Types for Selected Step: 
    Displacement base motion or Velocity base motion or Acceleration base motion
    Create Boundary Condition; Step: step; Category: Mechanical; Types for Selected Step: 
    Secondary base 
Step module, Interaction module, or Load module:
    ToolsAmplitudeCreate; Type: PSD Definition