Hi,

I have a mechanical structure mounted on vibration isolators.

In Abaqus, I have modelled the vibration isolators as Bushing, with stiffness and damping values.

Additionally, I am defining structural damping during the Step definition.

I am extracting, 10 modes in the frequency extraction. The first 6 modes are due to the isolators and next 4 modes are structural modes. The eigen frequencies are in the expected range.

For the steady state dynamic response (modal) analysis, the system response are as expected, that is it corresponds to the damping defined in the bushing element.

But when doing random response analysis, the damping defined in the bushing is not considered by the solver and the response values corresponds to the structural damping.