The use of seismic isolators does not mean the equipment is IBC compliant. The confusion with seismic vibration isolators is that people often refer to them as “seismic isolators.” This term infers that their intended function is to isolate or reduce the effects of a seismic event. A seismic vibration isolator is not designed to reduce these harmful effects. At best, properly designed seismic vibration isolators will not amplify the effects of the earthquake into the system; however, they will transfer the seismic forces from the building structure into the equipment. This is the very reason that equipment manufacturers are analyzing and testing their equipment to meet certain seismic design forces. If seismic vibration isolators actually reduced the g-levels into equipment, the building codes would require everything to be “seismically isolated” rather than be designed to survive the effects of an earthquake.
 
Seismic vibration isolators do have a function when it comes to a properly designed seismic system. When vibration isolation is required on a project to minimize the harmful noise and vibration created by a generator set from entering the building structure, then seismic vibration isolators are required in seismic areas of the country. A properly designed seismic vibration isolator will reduce the noise and vibration emanating from the equipment during normal operation and will also keep the equipment properly attached to the building structure in the event of an earthquake. This style of vibration isolator must be captive in design and constructed to handle the overturning moments of the generator set when a seismic design force is applied to the center of gravity of the equipment. The design should incorporate no more than a ¼” gap in the horizontal directions and a snubbing device to minimize the amplification of the earthquake forces into the equipment.
 
If vibration isolation into the structure is not a concern of the design engineer, then the requirements for the project should only be proper attachment to the building structure. This includes analyzing the resulting overturning forces of the generator set based on the seismic site conditions of the project and then properly selecting an anchorage that can handle these forces.