where:

uniform lateral shear load on the

diaphragm, K/ft. (N/m).

noting that:

Where *t *is the thickness of the web, and *D *is the

depth of the diaphragm, the formula for shearing

effective shear modulus calculated

deflection can also be expressed as:

from tabulated values based on profile and thickness

of deck and type and spacing of connectors.

∆ω

= ave 1

(7-8)

The effective shear modulus , *G*' is related to the

,

flexibility factor, *F*, as follows:

As noted above, this is only applicable to webs of

uniform properties. For a concrete slab with *" *= 1.5,

3

(7-11)

1.5

'

f , the formula in

English units becomes:

A deep-beam

analogy is used in the design.

Diaphragms are

∆ω =

(7-9)

envisioned as deep beams with the web (decking or

1.5

'

8.8*tw*

f .

sheathing) resisting shear and the flanges (spandrel

beams or other members) at the edges resisting the

where:

bending moment.

(1) Unit shears. Diaphragm unit shears are

obtained by dividing the diaphragm shear by the

length or area of the web, and are expressed in

pounds per foot (N/m) (for wood and metal decks) or

Recent editions of the SDI Diaphragm Design

pounds per square inch (MPa) (for concrete). These

Manual provide the following alternative equation for

unit shears are checked against allowable values for

the deflection of steel deck diaphragms:

the material.

Webs of precast concrete units or

metal-deck units will require details for joining the

2

units to each other and to their supports so as to

)w =

(7-10)

8*DG * '

distribute shear forces.

7 -121

Integrated Publishing, Inc. |