Page 166 - Handbook of Civil Engineering Calculations, Second Edition

STRUCTURAL STEEL DESIGN 1.149

e x e cos 45° 6 in. 0.707 4.2 in. (10.7 cm)
e y e sin 45° 6 in. 0.707 4.2 in. (10.7 cm)
100 kips × 4.2 in.
M ux P u e x 35.4 kip-ft (48 kNm)
12 in.ft
100 kips × 4.2 in.
M uy P u e y 35.4 kip-ft (48 kNm)
12 in.ft
Again, try a W8 48. As above
P u 100 kips
+ 0.22 > 0.2
t P n 457
t M ny 61.8 kip-ft (83.8 kNm)

Although the W8 48 is not listed in the Beam Selection Table in the AISC LRFD Man-
ual, L p and b M nx can be calculated. From Eq. (Fl-4) (Chap. 5):
300r y 300r y
L p

F y 36 50r y

50 2.08 in. 104 in. 8.7 ft (2.65 m)
Since (L b 6.0 ft) < (L p 8.7 ft)

b M nx b M p b Z x F y
3
0.90 × 49.0 in. × 36 ksi
132 kip-ft (178.9 kNm)
12 in.ft
In Interaction Formula (H1-1a)
8 35.4 kip-ft 35.4 kip-ft
0.22 + + 1.0
9
132 kip-ft 61.8 kip-ft
0.22 + /9(0.27 + 0.57)
8
0.22 + 0.75 0.97 < 1.0 o.k.

The most efficient configuration is orientation (a), strong axis bending, which requires a
W8 28 as opposed to a W8 48 for the other two cases.
Related Calculations. This procedure is the work of Abraham J. Rokach, MSCE, As-
sociate Director of Education, American Institute of Steel Construction. SI values were
prepared by the handbook editor.

COMBINED FLEXURE AND COMPRESSION
IN BEAM-COLUMNS IN A BRACED FRAME

Select, in A36 steel, a W14 section for a beam-column in a braced frame with the follow-
ing combination of factored loads: P u 800 kips (3558 kN); first-order moments