For a Dynamic Random analysis the loads are input as a Power Spectral Density (PSD) over a frequency range. The load may be Base Accelerations (G^2/Hz) or Forces (Load^2/Hz) applied to the structure. Base Accelerations are applied to any Constraints or Springs-to-Ground. In a Dynamic Random analysis the loads are applied at all frequencies simultaneously. The result is more statistical rather than an absolute number. The PSD response or RMS value may be calculated at a particular location using a Measure. The RMS response of the full structure may also be calculated and displayed. This type of analysis is often used for simulation of transportation or acoustic environments where the loads are continuous, long duration and random.
