PROBLEM $8\mathrm{.}6$

$($a$)$ Knowing that ${}_{\text{a}\text{l}\text{l}}=24$ksi and ${}_{\text{a}\text{l}\text{l}}=14\mathrm{.}5$ksi, select the most

economical wide$-$flange shape that should be used to support the loading

shown. $($b$)$ Determine the values to be expected for ${}_m,{}_m,$ and the

principal stress ${}_{\text{m}\text{a}\text{x}}$ at the junction of a flange and the web of the

selected beam.