design displacement in the horizontal direction

isolation system shall be designed and constructed to

withstand a minimum lateral seismic force, *V*s, using

under consideration.

all of the appropriate provisions for a nonisolated

structure, where:

at the center of rigidity of the isolation system in the

direction under consideration as prescribed by

(8-7)

Equation 8-1.

where:

numerical coefficient related to the

maximum effective stiffness, in

type of lateral-force-resisting system above the

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

isolation system.

design displacement in the horizontal direction under

The *R*I factor shall be based on the type of lateral-

consideration.

force-resisting system used for the structure above

the isolation system and shall be 3/8 of the *R *value

at the center of rigidity of the isolation system in the

given in Table 7-1, with an upper-bound value not to

direction under consideration as prescribed by

exceed 2.0, and a lower-bound value not to be less

Equation 8-1.

than 1.0.

In all cases, *V*b shall not be taken as less than the

(4) Vertical distribution of force. The total

maximum force in the isolation system at any

force shall be distributed over the height of the

displacement, up to and including the design

structure above the isolation interface in accordance

displacement.

with the following equation:

(b) Structural elements above the isolation

(8-9)

system.

The structure above the isolation system

n

∑wh

i

i

shall be designed and constructed to withstand a

i=1

minimum shear force, *V*s, using all of the appropriate

provisions for a nonisolated structure, where:

where:

(8-8)

shear on elements above the isolation system as

prescribed by Equation 8-8.

where:

portion of *w *that is located at or

assigned to Level *x*.

maximum effective stiffness, in

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

8 - 16

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