(c) Maximum displacement. The maximum

Motion A or Ground Motion B, as defined in Chapter

displacement of the isolation system, *D*M, in the most

4.

critical direction of horizontal response shall be

calculated in accordance with the formula:

seismically

isolated

structure

at

the

design

displacement in the direction under consideration, as

* g*

2 *S * M 1TM

prescribed by Equation 8-2.

4*π *

(8-3)

effective damping of the isolation system at the

where:

design displacement, *$*D, as set forth in Table 8-1.

(b) Effective period. The effective period of

the isolated structure, *T*D, shall be determined using

units of the design displacement, *D*D, are inches

the deformational characteristics of the isolation

(mm).

system in accordance with the following equation:

maximum considered 5 percent

damped spectral acceleration at 1-second period as

(8-2)

determined in Chapter 3.

effective period, in seconds, of

where:

seismic-isolated

structure

at

the

maximum

displacement in the direction under consideration as

prescribed by Equation 8-4.

structure above the isolation interface as defined in

Sections 5.3.2 and 5.5.3 of FEMA 302 (kip or kN).

effective damping of the isolation system at the

maximum displacement, *$*D, as set forth in Table 8-1.

kips/inch (kN/mm), of the isolation system at the

design displacement in the horizontal direction under

(d)

Effective

period

at

maximum

consideration.

displacement. The effective period of the isolated

structure at maximum displacement, *T*M, shall be

determined using the deformational characteristics of

the isolation system in accordance with the equation:

units of the design displacement, *D*D, are inches

(mm).

(8-4)

8 - 14

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