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Calculate service load moments:

Mx — Mx,dead + Mx,live = 20 + 50 = 70 k ft My — My,dead + My,live = 5 + 15 = 20 k ft

Select section: Substituting the above service load moments into Equation 4.78, we have

70 x 12 20 x 12 Sx --1--< 0 .60(50) or 840 + 240— < 30Sx

Sx Sy Sy

For W-sections with depth below 14 in. the value of Sx/Sy normally falls in the range 3 to 8, and for W-sections with depth above 14 in. the value of Sx/Sy normally falls in the range 5 to 12. Assuming SxISy — 10, we have from the above equation, Sx > 108 in.3 Using the ASD Selection Table in the AISC-i/Toninl lot nc tnr o \K7~> A x ££ co^ti'rjn (Sx — 114 in 3, Sy -

The next lightest section is W21 x 62 (Sx — 127 in.3, Sy — 13.9 in.3). For this section

ASD Manual, let us try a W24 x 55 section (Sx = 114 in.3, Sy = 8.30 in.3). For the W24 x 55 section

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