nonlinear response of the seismic framing.

One

procedure for evaluating the target displacement for

1

(5-6)

an individual line of vertical seismic framing is

given by Equation 5-5. The fundamental period of

each vertical line of seismic framing, for calculation

where *S*a and *C*0 are defined above, and:

of the target displacement, shall follow the general

procedures described for the Nonlinear Static

Procedure; masses shall be assigned to each level of

of Nonlinear Static Procedure, where the nonlinear

the mathematical model on the basis of tributary

force-displacement (i.e., base shear force versus

area. For a building with neither rigid nor flexible

control node displacement) curve of building is

diaphragms

at

each

floor

level,

the

target

characterized by a bilinear relation (Figure 5-3).

displacement shall be calculated using rational

procedures. One acceptable procedure for including

the effects of diaphragm flexibility is to multiply the

load.

displacement calculated using Equation 5-5 by the

ratio of the maximum displacement at any point on

Coefficient *C*3 shall be calculated as follows if the

the roof, and the displacement of the center of mass

relation between base shear force and control node

of the roof, both calculated by modal analysis of a

displacement exhibits negative post-yield stiffness.

three-dimensional model of the building using the

design response spectrum. The target displacement

3

so calculated shall be no less than that displacement

2

(5-7)

given by Equation 5-5, assuming rigid diaphragms at

each floor level. No vertical line of seismic framing

shall be evaluated for displacements smaller than the

where *R *and *T*e are defined above, and:

target displacement.

" = ratio of post-yield stiffness to effective

elastic

stiffness,

where

the

nonlinear

force-

displacement relation is characterized by a bilinear

relation (Figure 5-3).

Under the Nonlinear Dynamic Procedure, design

seismic forces, and the corresponding internal forces

For a building with flexible diaphragms at each floor

and system displacements are determined using an

level, a target displacement shall be estimated for

inelastic response history dynamic analysis.

The

each line of vertical seismic framing. The target

basis, modeling approaches, and acceptance criteria

displacements

shall

be

estimated

using

an

for the Nonlinear Dynamic Procedure are similar to

established procedure that accounts for the likely

those of the Nonlinear Static Procedure. The main

5-17

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