SPECIFICATION FOR THE DESIGN OF - Transcon Steel

70 Commentary on the Prescriptive Method for One and Two Family Dwellings - 2004
Diaphragm Loads 50’
W px2
F px =
n
∑
i=
x
n
∑
i=
x
F
W
x
i
W
px
30’
W px1
V px2
V px2
V px1
V px1
Diaphragm
F x W x
(lb) (lb)
Roof 9,638 36,330
2 nd Floor 3,799 32,580
W px
ΣF i
ΣW i
F px V px
(lb)
(lb)
(lb) (lb) (lb/ft)
W px1 =34,440 9,638 36,330 9,137 152
W px2 =33,180
8,802 88
W px1 =28,800 13,437 68,910 5,616 94
W px2 =26,280
5,124 51
Compare with 0.15(S DS I E W px ) and 0.3 (S DS I E W px ) (IBC Eq. 1620.3.3)
S DS = 1.17; I E = 1.0
0.15(S DS I E W px ) 0.3 (S DS I E W px )
Roof 6,044 lb < 9,137 lb < 12,088 lb ok
2 nd 5,054 lb < 5,616 lb < 10,109 lb ok
Diaphragm Chord Splice Requirements
Determine Chord Force and Splice Requirements with Amplified Chord Force
Diaphragm
W p
(lb/ft)
L
(ft)
C=T (lb) Ω 0 Ω 0 T Required No. 8
Screws @ Splice
Roof 183 50 1,906 2.5 4,765 20
293 30 659
1,648 7
2 nd Floor 113 50 1,177 2.5 2,943 12
W p = F px /L; C=T= W p L 2 /8L 2
171 30 385
963 4
Note: Ω 0 = 2.5 based on system 1.K from Table 1617.6 of the IBC 2000 with 0.5
reduction for flexible diaphragm (3.0 – 0.5 = 2.5)
Note: For No. 8 screws, assuming 33 mil top track:
Φ = 0.5 for screws in shear
V n = 492 lb
Φ V n = 246 lb