I am running a Linear Dynamic Study with a Random input. I am
using a Uniform Base Excitation as an input to the system so that I
can create a power spectral density (PSD) output. I need to enter
acceleration, and so the dropdown box under "PSD Acceleration" on
the "Uniform Base Excitation" menu gives the units of g^2/Hz. This
is confusing. The imput excitation should be an acceleration with
units of "g" or "m^2/s". The output of a PSD can be g^2/Hz, but
this unit assumes that I know what the width of my discretization
is (for example, if I solve every 10Hz, then my output is g^2/10Hz
which averages the g^2 value across the 10Hz window). When I'm
entering the input acceleration, I don't know what the frequency
discretization width is.
So, is the acceleration input on this page really in g's and it is
just labeled for what the output of the PSD is going to be? Am I
supposed to run the whole analysis, see what the discretization
width is, and then come back to change my input correctly? What's
going on here?
Thanks for the help.