AC156 protocol by ICC-ES is finalised to seismic certification of nonstructural components by shake table testing. According to the field literature, there are several cases in which such protocol is used with reference to un-anchored components (e.g., free to experience rocking motion). In this latter case, the natural vibration period of the component (fundamental feature for the application of the protocol) is not really affecting the actual "dynamic resonance" or, more in general, the experimental seismic response (especially for moderate-to-high intensity excitation). This is due to the potential motion of the component under dynamic excitation; such motion is reasonably governed by periods that are significantly lower than the typical natural vibration periods.

AC156 does not state the inapplicability of the protocol to freestanding components: the main limitation feature is the component vibration period. But the significance of the vibration periods on the dynamic response of the component is reduced if the motion of the latter is potentially experienced (no fasteners or connectors). On the other side, AC156 represents the State-of-art or, maybe, the unique protocol for seismic certification (and not seismic assessment) of "generic" nonstructural components.

Overall, is the use of AC156 protocol for unattached components still reasonable, or, are there valid and authoritative alternatives, more conceived for such (specific!) typology of components?

Do the benefits of use of AC156 in such contexts (benefits, e.g., authoritative, used in literature, very strict, etc...) exceed the malefits (e.g., target spectrum ranging in frequencies larger than the potential motion frequency, protocol conceived for attached components, etc...)?

Many thanks in advance for time you will dedicate to this issue.

Danilo