SPECIFICATION FOR THE DESIGN OF - Transcon Steel

56 Commentary on the Prescriptive Method for One and Two Family Dwellings - 2004
⎛ Pu
⎞ ⎛ M
u
⎞
0.82
⎜
⎟ +
⎜
⎟ ≤ 1.32
⎝ Φ
wPn
⎠ ⎝ Φ
bM
nxo ⎠
(Eq. C3.5.2-2)
The following load model is used in checking the combined bending and web crippling
equation. The concentrated load is located at mid-span of the beam. The distributed
load is located one foot away from the concentrated load on each side (assuming a 2-foot
spacing).
P
L
Maximum moment, M =
PL ⎛ L − 2 ⎞⎛
L ⎞ ⎛ L − 2 ⎞⎡⎛
L ⎞ ⎛ L − 2 ⎞⎤
+ w⎜
⎟⎜
⎟ − w⎜
⎟⎢⎜
⎟ − ⎜ ⎟
4
⎥
⎝ 2 ⎠⎝
2 ⎠ ⎝ 2 ⎠⎣⎝
2 ⎠ ⎝ 2 ⎠ ⎦
Substitute for all the variables in Eq. B2.5-2 and solve for L.
where
M nxo = 6,333 ft-lb (Unfactored moment)
Φ w = 0.80 for back-to-back headers
Φ b = 0.95
P = 2(w) = 2,788 lbs
w = 1,394 plf
⎛ 2788 ⎞ ⎛ M
u ⎞
0.82⎜
⎟ + ⎜ ⎟ ≤ 1.32
⎝ 0.80x4064
⎠ ⎝ 0.95x6333
⎠
PL ⎛ L − 2 ⎞⎛
L ⎞ ⎛ L − 2 ⎞⎡⎛
L ⎞ ⎛ L − 2 ⎞⎤
Set M u = M = + w⎜
⎟⎜
⎟ − w⎜
⎟⎢⎜
⎟ − ⎜ ⎟
4
⎥
⎝ 2 ⎠⎝
2 ⎠ ⎝ 2 ⎠⎣⎝
2 ⎠ ⎝ 2 ⎠ ⎦
Solve the above equations for L.
L = 4’-1”
E4 Double L-Header Design (Gravity Loading)
Calculate the maximum allowable spans for a 2-800L150-54 double L-header supporting an
opening located at the roof level of the two-story building described in Section E2.
E4.1 Design Loads
Dead Loads:
Ceiling Dead Load = 5(24/2)
Roof Dead Load = 7(24/2)
Soffit Dead Load = 2(7)
Total Dead Load
= 60 plf
= 84 plf
= 14 plf
= 158 plf
Live Loads:
Roof Live Load = 16(28/2)
= 224 plf
Snow Load = 0.7(50)(28/2) = 490 plf controls