QUESTION $3$

a$)$

A rectangular concrete section has a width of $b=12in.(300mm),$ an effective depth of $d=18in.(450mm),$ and $d^{\text{'}}=2\mathrm{.}5in.(60mm).$ If compression steel consisting of two no$.7$ bars $(220mm)$ is used, calculate the allowable moment strength that can be applied on the section if the tensile steel, $A_s,$ is as follows:

a$.$ Four no$.7(420mm)$ bars

b$.$ Eight no$.7(820mm)$ bars

Given: $f_c^{\text{'}}=3$ksi$(20$MPa$)$ and $f_y=40$ksi$(300$MPa$).$

b$)$

Determine the design moment strength of the sections shown in Fig, $3\mathrm{.}41.$ Neglect the lack of symmetry in $($b$).$ Given: $f_c^{\text{'}}=4$ksi$(30$MPa$)$ and $f_y=60$ksi$(400$MPa$).$