Seismic Interaction

DOE-STD-1020-2002

PC-1 and PC-2 SSCs, seismic evaluation of equipment or nonstructural elements

supported by a structure can be based on the total lateral seismic force as given in the IBC. For

PC-3 and PC-4 SSCs, the seismic evaluation of equipment and distribution systems can

necessitate the development of floor response spectra representing the input excitation. Once

seismic loading is established, seismic capacity can be determined by analysis, testing, or, if

available, the use of seismic experience data. It is recommended that seismic evaluation of

existing equipment and distributions systems be based on experience data whenever possible.

C.6.2

Seismic Interaction

During the occurrence of an earthquake, it is possible for the seismic response of one

structure, system, or component to affect the performance of other structures, systems, and

components. This sequence of events is called seismic interaction. Seismic interactions which

could have an adverse effect on SSCs shall be considered in seismic design and evaluation of

DOE facilities. Cases of seismic interaction which must be considered include:

Structural failing and falling.

Proximity.

Flexibility of attached lines and cables.

Flooding or exposure to fluids from ruptured vessels and piping systems.

Effects of seismically induced fires.

Structural failing and falling is generally prevented by single-failure seismic design

criteria as described in other portions of this document. An interaction problem arises where a

higher category (such as Performance Category 4) SSC (target) is in danger of being damaged

due to the failure of overhead or adjacent lower category (such as Performance Category 1, 2, or

3) SSCs (source) which have been designed for lesser seismic loads than the higher category

SSC (target). Lower category items interacting with higher category items or barriers protecting

the target items need to be designed to prevent adverse seismic interaction. If there is potential

interaction, the source does not move to the performance category of the target but remains in its

own category based on its own characteristics. However, the source is subject to additional

seismic design requirements above those for its own performance category. These requirements

are that the source (or barrier) shall be designed to maintain structural integrity when subjected

to the earthquake ground motion associated with the performance category of the target.

Impact between structures, systems, or components in close proximity to each other due

to relative motion during earthquake response is another form of interaction which must be

considered for design and evaluation of DOE SSCs. If such an impact could cause damage or

failure, there should be a combined design approach of sufficient separation distance to prevent

impact, and adequate anchorage, bracing, or other means to prevent large deflections. Note that

even if there is impact between adjacent structures or equipment, there may not be potential for

any significant damage such that seismic interaction would not result in design measures being

implemented. An example of this is that a 1 inch diameter pipe cannot damage a 12 inch

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