Diaphragms With Vertical Offsets - The Analysis of Irregular Shaped Structures - page 260

Check:

9600
2

∑ 258 83 16

V = . () + 828 14 . () − = 2654 lb OK

F collector = ( 828 1 . − 258 83 . () 40 = 22 772 , lb com pression

Transfer wall at grid line B: The chord force to the wall is equal to 12,554 lb. The force at
the top of the wall from the diaphragm shears is equal to

281 2 . + 206 3 .

V 23 = () 30 = 7312 lb

−

2

12 554 , + 7312

v upper = = 662 2 . plfwallshear b etween upperand lowerchords

40

12 554 , + 7312 − 22 772 ,

v lower = =− 96 87 . plfwall shear belowlower chord

30

Wall dead load =7200 lb

∑

M 2 = 0 summing momentsabout grid line 2

1
30

F 3

=− [( . 12 554 + 7 312 . )( 20 ) + 318307215 2 772 . () .( ) + + . (( ] 16

= 5 681 . kcompression

∑

M 3 = 0 summing momentsabout grid line 3

1
30

F 2 =− [( . 12 554 + 7 312 . )( 20 ) − 7215 . () + 22 772 16 . ( )] = .kcompression 47

F collector = ( 662 2968730 2 772 . + . () = , lb tens ion

The hold-down connections for the clerestory walls and the transfer walls should be
determined using load case W + 0.6 D . ▲

7.4 Multiple Vertical Offsets in Diaphragm

It is important to have a good understanding of how multilevel diaphragm structures
respond to seismic forces. The computer software currently available to the engineer
provides the ability to easily perform a modal analysis, which will show the displaced
shape of the structure and provide a key to areas that require special attention. Most
complex structures are modeled using a three-dimensional computer analysis. The seis-
mic analysis for these structures is usually conducted internally in the first mode only,
unless specifically desired otherwise by the engineer. Occasionally, portions of complex
structures are analyzed by using a plane frame program along each line of resistance in