I would like to apply an acceleration or a velocity constraint in a harmonic analysis. My attempts to use D,ACCX or D,VELX have not been successful. What am I doing wrong?
The acceleration and velocity constraints (D,ACCX and D,VELX, respectively) are valid only for structural static and transient analyses (Basic Guide, Section 2.5). Remembering that a harmonic analysis assumes all loads vary sinusoidally, you will need to integrate the acceleration/velocity load and apply it as a displacement. In fact, the integration shows that only a simple division is required.
acceleration load (a = acceleration, v = velocity, u = displacement, w = omega = frequency, t = time):
a = A sin (wt)
v = A/w cos (wt)
u = -A/w/w sin (wt)
As a result, to apply an acceleration load of magnitude "A", simply set a displacement constraint with a magnitude of "-A/w/w".