SPECIFICATION FOR THE DESIGN OF - Transcon Steel

Commentary on the Prescriptive Method for One and Two Family Dwellings - 2004 53
d 0 /h = 1.5/7.722 = 0.19 < 0.7
h/t = 171.6 < 200
Holes centered at mid-depth of the web
Clear distance between holes ≥ 18”
Circular hole diameter ≤ 6”
Non-circular holes, hole depth (d 0 ) = 1.5” ≤ 2.5” and b = 4” ≤ 4.5”
d 0 > 9/16”
R c = 0.90 – 0.047d o /h + 0.053x/h ≤ 1.0
R c = 0.90 – 0.047(1.5)/7.722 + 0.053(10)/7.722 = 0.96
(Eq. C3.4.2-2)
P n = 1,960 x 0.96 = 1,882 lb
(for 2 webs with punchouts)
⎛ Pu
⎞ ⎛ M
u
⎞
1.07
⎜
⎟ +
⎜
⎟ ≤ 1.42
⎝ Φ
wPn
⎠ ⎝ Φ
bM
nxo ⎠
(Eq. B2.5-2)
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 = 0.75 for box-beam headers
Φ b = 0.95
P = 2(w) = 2,788 lbs
w = 1,394 plf
⎛ 2788 ⎞ ⎛ M
u ⎞
1.07⎜
⎟ + ⎜ ⎟ ≤ 1.42
⎝ 0.75x1882
⎠ ⎝ 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.