Seismic Design/Evaluation Input

DOE-STD-1020-2002

exceedance is illustrated in Figure C-3. Earthquake input excitation to be used for design and

evaluation by these provisions is defined by a median amplification smoothed and broadened

design/evaluation response spectrum shape such as that shown in Figure C-3 anchored to this

maximum ground acceleration. Note that the three spectra presented in Figure C-3 are identical;

the top spectrum has spectral acceleration plotted against natural frequency on a log scale, the

middle spectrum is on what is termed a tripartite plot where spectral velocities and displacements

as well as accelerations are shown, and the bottom spectrum has spectral acceleration plotted

against natural period on a linear scale.

It should be understood that the spectra shown in Figure C-3 represent inertial effects.

They do not include relative or differential support motions of structures, equipment, or

distribution systems supported at two or more points typically referred to as seismic anchor

motion (SAM). While SAM is not usually applicable to building design, it might have a

significant effect on seismic adequacy of equipment or distribution systems.

Seismic design/evaluation criteria based on target probabilistic performance goals

requires that Design/Evaluation Basis Earthquake (DBE) motions be based on probabilistic

seismic hazard assessments. In accordance with DOE Order 420.1 and the associated Guide

(Ref. C-27 and C-67), it is not required that a site-specific probabilistic seismic hazard

assessment be conducted if the site includes only PC-1 and PC-2 SSCs. If such an assessment

has not been performed, it is acceptable to determine seismic loads (as summarized in Section

C.3.2.2) from those determined in accordance with the IBC (Ref. C-28). Design/evaluation

earthquake ground motion determined from a recent site-specific probabilistic seismic hazard

assessment is considered to be preferable to the IBC 2000 but cannot be lower than limitations in

the IBC 2000.

For design or evaluation of SSCs in Performance Category 3 and higher, a modern

site-specific seismic hazard assessment shall be performed to provide the basis for DBE ground

motion levels and response spectra (See DOE-STD-1023). DOE Order 420.1 and the associated

NPH Guide (Refs. C-27 and C-67), require that the need for updating the site seismic hazard

assessment be reviewed at least every 10 years.

Minimum values of the DBE are provided in Section 2.3 to assure a minimum level of

seismic design at all DOE sites. Such a minimum level of seismic design is believed to be

necessary due to the considerable uncertainty about future earthquake potential in the lower

seismicity regions of the United States where most DOE sites are located.

C-12