No. 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). In a harmonic analysis all loads are assumed to vary sinusoidally. You need to integrate the acceleration/velocity load and apply it as a displacement. The integration only requires a simple division. 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”.