Example $1($Concrete mix design$)$

Given:

Portland cement $)$

Aggregate : mixture of sand & sandy gravel

$\backslash$table$[[$Sieve size $(mm),0\mathrm{.}25,0\mathrm{.}50,1,2,4,8,16,$

Hibbeler $4-61.$ The distributed loading is supported by the three suspender bars. $AB$ and $EF$ are made of aluminum and $CD$ is made of steel. If each bar has a cross$-$sectional area of $450m{m}^2,$ determine the maximum intensity $w$ of the distributed loading so that an allowable stress of $({}_{\text{a}\text{l}\text{l}\text{o}\text{w}}{)}_{st}=180$ MPa in the steel and $({}_{\text{a}\text{l}\text{l}\text{o}\text{w}}{)}_{al}=94$MPa in the aluminum is not exceeded. $E_{St}=200$GPa,$E_{al}=70$GPa. Assume ACE is rigid.