I am dealing with a steel frame that supports a piece of equipment (crusher). This crusher moves in the X & Y axis while operating. The manufacturer has given me equivalent "static" loads to use in order to account for the dynamic loads transmitted to the frame while operating. The operating frequency of the crusher is roughly 450 RPM = 7.5 CPS = 7.5 Hz.
I am somewhat confused as to what "masses" need specified for this analysis.
If I specify a selfweight factor of 1.0 in the X, Y & Z directions, that activates the mass matrix for each direction, and I will get mode shapes & frequencies in all three directions. I can look at the various mode shapes and frequencies and compare them to the operating frequency of the crusher to make sure that it's "well removed".
However......what about the actual crusher loads? Do they need considered in this modal analysis? They're not really a "mass", but adding them certainly can change the results. For example, let's say I added the vertical weight of the crusher (Y), the vertical dynamic load of the crusher (Y), and the horizontal dynamic load of the crusher (X). Is that what is required to get a correct modal analysis?