damping modification factor, *B*, and either *B*s or *B*l,

the viscous forces so that the horizontal displacement

for periods in the vicinity of the mode under

of each floor level is zero.

consideration; note that the value of B will be

different for each mode of vibration. The damping

iii.

At the stage of maximum floor

acceleration**. **Design actions in components of the

modification factor in each significant mode should

be determined using Table 8-2 and the calculated

rehabilitated building should be determined as the

effective damping in that mode.

The effective

sum of [actions determined at the stage of maximum

drift] times [*CF*1] and [actions determined at the stage

damping should be determined using a procedure

of maximum velocity] times [*CF*2], where

similar to the described in Paragraph 8-4e(2)(a).

[

]

2.

If the maximum base shear force

(8-23)

calculated by dynamic analysis is less than 80 percent

of the modified equivalent base shear of Paragraph 8-

[

)]

-1

(8-24)

4e(2)(a), component and element actions and

deformations shall be proportionally increased to

in which *$*eff is defined by either Equation 8-20 or

correspond to 80 percent of the modified equivalent

Equation 8-22.

base shear.

(3) Linear Dynamic Procedure (LDP). The

(b) Velocity-dependent devices.

modal analyses procedure, described in Paragraph 3-

2(c)(2), may be used when the effective damping in

1. For analysis by the Response Spectrum

the fundamental mode of the building, in each

Method, the 5 percent damped response spectrum

principal direction, does not exceed 30 percent of

may be modified to account for the damping afforded

critical.

by the velocity-dependent energy dissipation devices.

The 5 percent damped acceleration spectrum should

(a)

Displacement-dependent

devices.

be reduced by the modal-dependent damping

Application of the LDP for the analysis of buildings

modification factor, *B*, either *B*s or *B*l, for periods in

incorporating displacement-dependent devices is

the vicinity of the mode under consideration; note

subject to the restrictions set forth in Paragraph 8-4-

that the value of *B *will be different for each mode of

e(2)(a).

vibration. The damping modification factor in each

significant mode should be determined using Table 8-

1. For analysis by the Response Spectrum

2 and the calculated effective damping mode.

Method, the 5 percent damped response spectrum

may be modified to account for the damping afforded

The effective damping in the *m*-th

2.

the

displacement-dependent

energy-dissipation

mode of vibration (*$*eff-m) shall be calculated as:

devices.

The 5 percent damped acceleration

spectrum should be reduced by the modal-dependent

8 - 35

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