Fpx

The resultant of the diaphragm load acting

through the center of mass (kips or K-N).

Ft

The force on an individual vertical resisting

Area of nonprestressed tension reinforcement (in.2

AS

element due to a torsional moment Mt

or mm2).

(kips or K-N).

Area of compression reinforcement (in.2 or mm2).

A'

S

Fv

Velocity-based site coefficient (at 1.0 sec period).

Gross cross-sectional area (in.2or mm2).

Ag

Fxm

The portion of the seismic base shear, Vm, induced

at level x as determined in paragraph 3-2c.

Aw

Area of the diaphragm web in Equations 5-10 and

5-11 (in.2 or mm2).

Fy

Specified yield strength of structural steel

(psi or MPa).

a

Angle of the diagonal members with the

horizontal plane in the special segment of a truss

Fye

Expected yield strength of structural steel

moment frame (degrees or radians).

(psi or MPa).

aw

Spacing of marginal welds in steel deck

fa

Axial stress in a structural member (psi or MPa).

diaphragm in Equation 5-14 (ft or m).

fae

Expected vertical compressive stress (psi or MPa).

bf

Flange width of structural steel beam (in. or mm).

fme

Expected compressive strength of masonry as

b/t

Ratio of flange width to flange thickness for

determined in Section 7.3.2.1 (psi or MPa).

structural steel beams.

Shear modulus (lb/in.2 or MPa).

G

Cd

The deflection amplification factor as given in

Table 7-2.

H

Thickness of soil (ft. or m).

Cs

The seismic response coefficient (dimensionless)

heff

Height to resultant of lateral force for wall or pier

determined in paragraph 3-2c.

(in. or mm).

Csm

The modal seismic response coefficient

K

Stiffness of a vertical resisting element in

(dimensionless) determined in paragraph 3-2c.

paragraph 5-9b(3)(d) (kips/in. or K-N/mm).

The vertical distribution factor in the mth mode.

Cvxm

LI

Distance from adjacent vertical resisting element

(i.e. such as a shear wall) and the point at which

cm

Center of mass.

the deflection is to be determined (ft or m).

cr

Center of rigidity.

L

Length of wall (in. or mm).

d

Distance of a vertical resisting element from the

L

single span length of a diaphragm in Equation 5-

center of rigidity in a torsional analyses

10 (ft or m).

(in. or mm).

L

Span length of truss in a truss moment frame

EI

Flexural elastic stiffness of the chord member of

(in. or mm).

the special segment of a truss moment frame

(kips - in.2 or (N-mm2).

Lp

Limiting laterally unbraced length for full plastic

flexural strength, uniform moment case

F

Flexibility factor in paragraph 5-9b(4)(b)

(in. or mm).

(micro in./ft, or mm/m).

Ls

0.9 times the length of the special segment in a

Fa

Acceleration-based site coefficient

truss moment frame (in. or mm).

(at 0.3 sec period).

B-1

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