Damping Values for Performance Category 3 and 4 Structures, Systems, and Components

DOE-STD-1020-2002

2.3.3 Damping Values for Performance Category 3 and 4 Structures,

Systems, and Components

Damping values to be used in linear elastic analyses are presented in Table 2-2 at three

different response levels as a function of DT/CC.

DT is the elastically computed total demand,

DT = DNS + DS

(2-4)

and CC is the code specified capacity.

When determining the input to subcomponents mounted on a supporting structure, the

damping value to be used in elastic response analyses of the supporting structure shall be based

on the response level reached in the majority of the seismic load resisting elements of the

supporting structure. This may require a second analysis.

In lieu of a second analysis to determine the actual response of the structure, Response

Level 1 damping values may be used for generation of in-structure spectra. Response Level 1

damping values must be used if stability considerations control the design.

When evaluating the structural adequacy of an existing SSC, Response Level 3 damping

may be used in elastic response analyses independent of the state of response actually reached,

because such damping is expected to be reached prior to structural failure.

When evaluating a new SSC, damping is limited to Response Level 2. For evaluating the

structural adequacy of a new SSC, Response Level 2 damping may be used in elastic response

analyses independent of the state of response actually reached.

The appropriate response level can be estimated from the following:

Response Level

DT/CC

3**

≥1.0

≈0.5 to 1.0

≤ 0.5

Consideration of these damping levels is required only in the generation of floor or

amplified response spectra to be used as input to subcomponents mounted on the

supporting structure. For analysis of structures including soil-structure interaction

effects (See C.4.3), DT/CC ratios for the best estimate case shall be used to determine

response level.

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