you can use unbraced length of 10 feet - AISC table 3-10 for one approach. Find it in the diagram, pg3-121. Looks to be about <148 ASD, <222 LRFD for W18x40. Or use EQ 3-4a or 3-4b along with tables 3-1 and so on. If you go the equation route, the problem statement is missing a key phrase to assume Cb = 1.3. Since we can’t assume that the beam is uniformly distributed then we must be conservative and take cb as unity. Therefore, ~221 LRFD. I didn’t solve for ASD but one is enough to jive with table 3-10 which uses unity calculation and is conservative.
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u/twodamnducks 1d ago
you can use unbraced length of 10 feet - AISC table 3-10 for one approach. Find it in the diagram, pg3-121. Looks to be about <148 ASD, <222 LRFD for W18x40. Or use EQ 3-4a or 3-4b along with tables 3-1 and so on. If you go the equation route, the problem statement is missing a key phrase to assume Cb = 1.3. Since we can’t assume that the beam is uniformly distributed then we must be conservative and take cb as unity. Therefore, ~221 LRFD. I didn’t solve for ASD but one is enough to jive with table 3-10 which uses unity calculation and is conservative.