Open Front and Cantilever Diaphragms - The Analysis of Irregular Shaped Structures - page 223

F =- 3575 + 243 86 10 . () = - 1076 4 . lb compression at enddofSW4

F =- 1076 4 25 40 2 . - ( . + )() =- 1261 4 . bcompression attstart of SW3

F =- 1261 4 . + 243 86 12 . () =+ 1664 96 . lbtension at endofSW3

F B =+ 1664 96 . -+ ( 40 52 5180 .)() = lb at grid lineB

Therefore the diagram closes. ▲

6.5 Cantilever Diaphragm One Side

The prescriptive requirements for cantilever diaphragms are covered in AF&PA SDPWS
Section 4.2.5.2 and referenced in Fig. 4B of that publication. For cantilever diaphragms,
the length of the cantilever shall be less than or equal to 25 ft or two-thirds of the width,
whichever is less, as shown in Fig. 6.11. For loads applied parallel to the numbered grid
lines, the diaphragm boundaries occur at grid lines A and C from 1 to 2. For loads
applied parallel to the lettered grid lines, the diaphragm boundaries occur at grid
lines A, B, and C from 1 to 2. In accordance with code, each boundary line must include
boundary members consisting of drag struts or collectors, or other lateral-force-resisting
elements such as shear walls or frames.

F i g u r e 6.11 Cantilever diaphragm, code requirements.