E = ρQE - 0.2SDSD

(Eq C-11)

The effects of gravity load (dead, live and snow load) and seismic forces shall be combined as follows

when the effect of gravity and seismic loads are additive, by combining Equations C-8 and C-10:

(1.2 + 0.2SDS )D + 0.5L + 0.2S + ρQE

(Eq C-12)

The effects of gravity load and seismic forces shall be combined as follows when the effect of gravity

and seismic loads counteract each other, by combining Equations C-9 and C-11:

(0.9 - 0.2SDS )D + ρQE

(Eq C-13)

For both expressions in Equations C-12 and C-13, the total horizontal force is ρQE. This force alone

defines the total lateral load that must be resisted by the shear panel diagonal straps or full panel sheets,

and these elements should be sized based on this force.

The effect of seismic loads, E shall be defined as follows, to account for diagonal strap overstrength

when the effect of gravity and seismic loads are additive:

E = Ω 0 QE + 0.2SDS D

(Eq C-14)

Where:

Ω 0 = the system overstrength.

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

counteract each other:

E = Ω 0 QE - 0.2S DSD

(Eq C-15)

The term Ω 0QE calculated in Equations C-14 and C-15 (TI 809-04, Equations 4-6 and 4-7) need not

exceed the maximum force that can be developed in the diagonal straps, based on the maximum

estimated ultimate strength of these elements. This is expressed as follows:

W

Ω 0QE ≤ Qu = Fsumax nsb s t s

(Eq C-16)

H + W

2

2

Where:

Fsumax = the maximum ultimate stress of the diagonal straps, which equals 1.5 Fsu for ASTM

A653 Grade 33 steel (Fsu = 310 MPa and 45 ksi) and 1.25 Fsu for Grade 50 steel (Fsu = 448

MPa and 65 ksi).

ns = the number of diagonal straps.

bs = the width of the diagonal straps.

ts = the thickness of the diagonal straps.

W = the overall panel width.

H = the overall panel height (see Figure 3-2 for a schematic panel drawing showing W and H).

The effects of gravity load (dead, live and snow load) and seismic forces shall be combined as follows to

account for diagonal strap overstrength, when the effect of gravity and seismic loads are additive, by

combining Equations C-8 and C-14:

(1.2 + 0.2SDS )D + 0.5L + 0.2S + Ω 0 QE

(Eq C-17)

C-5

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