ρ shall be taken as 1.0. For structures in categories D, E and F, values for ρ shall be taken as the largest

of the values of ρ x calculated for each story of the structure " "as follows (FEMA 302, Equation 5.2.4.2):

x

C1

ρx = 2 -

(Eq C-7)

rmax x A x

Where:

rmaxx = the ratio of design story shear resisted by the single shear panel carrying the most shear

force in the story to the total shear story, for a given direction of loading. Lateral loads shall

be distributed to panels based on relative stiffness considering the interaction of panels with

varying stiffness.

Ax = the floor area in m2 (ft2) of the diaphragm level immediately above the story.

ρ need not exceed 1.5, and may be used for any structure. The value of ρ shall not be taken as

less than 1.0.

C1 = constant, 6.1 metric, (20 English)

C5. LOAD COMBINATIONS. Consideration of combinations of loads in the two orthogonal directions is

not needed. The effects of gravity loads and seismic forces shall be combined in accordance with the

1.2D + 1.0E + 0.5L + 0.2S

(Eq C-8)

and

0.9D + 1.0E

(Eq C-9)

Where:

D = the dead load.

E = the effect of seismic load.

L = the live load the load factor on L in Equation C-8 shall equal 1.0 for garages, areas

occupied for public assembly, and all areas where the live load is greater than 4.79 kN/m2

(100 psf).

S = the snow load when the flat roof snow loads exceed 1.44 KN/m2 (30 psf), the full design

snow load shall be included in Equation C-8.

The effect of seismic loads, E shall be defined as follows, when the effect of gravity and seismic loads

are additive (FEMA 302, 5.2.7):

E = ρQE + 0.2SDSD

(Eq C-10)

Where:

E = the effect of horizontal and vertical earthquake-induced forces.

ρQE = the maximum horizontal force that could be resisted by the bracing.

ρ = the system redundancy factor.

QE = the effect of horizontal seismic forces.

D = the effect of dead load.

The effect of seismic loads, E shall be defined as follows, when the effect of gravity and seismic loads

counteract each other:

7

Minimum Design Loads for Buildings and Other Structures, ASCE 7-95, Section 2.3.2.

C-4

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