(2)

Actions and Deformations.

With the

deformations

by

subtraction

of

the

yield

procedures

as

described

in

Paragraph

5-4,

deformations, 2 y.

compliance with the performance objective requires

compliance with the global displacement criteria for

i. For beams:

the structure as a whole, and the local deformation

criteria for individual structural elements.

ZFye l b

(6-7)

2y=

6EI b

(a) Global displacement. The displacement

for the control node of the structure in the

ii. For columns:

force/displacement plot (i.e., pushover analysis) must

equal or exceed the target displacement, *δ *described

ZFyelc

P

1 -

(6-8)

2y=

6EIc Pye

in Paragraph 5-4f. Story drifts shall not exceed the

values indicated in Table 6-1.

where:

(b)

Deformation-controlled

actions.

Primary and secondary components shall have

Z = Plastic section modulus, in3 (mm3).

expected deformation capacities not less than the

deformations derived from the pushover analysis

Fye = Expected yield strength, psi (kPa), as

when the target displacement, *δ *is attained.

defined in the AISC Seismic provisions.

Modeling parameters and numerical acceptance

criteria are provided for each performance objective

Moment of inertia of beams, in4

Ib =

for the structural systems described in Chapters 7

(mm4).

through 10. The acceptance criteria are provided in

Ic = Moment of inertia of columns, in4

or deformation ratios ) /) y, as depicted in Figure 6-2.

(mm4).

1.

Steel moment and braced frames.

lb = Beam length, in (mm).

Acceptance criteria are provided in terms of either

plastic rotations of ratios or plastic rotations to yield

lc = Column length, in (mm).

rotations.

Figure 6-3 illustrates the definition of

chord rotation for frame beams and columns. If it is

P = Axial force in the columns, kips (kN).

assumed that the total chord rotation, 2 , (elastic plus

plastic rotation) is defined by the interstory drift,

Pye = Expected axial yield strength, Ag Fye

) /h, then the interstory drift ratio becomes a

kips (kN).

convenient parameter to monitor the inelastic

6 - 10

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