Practice Problems $-1$

$2-1.$ a$.$ The beam of the cross section shown has $f_r=3000$ and $f_y=60,000.$ Neglect the tensile strain check and $A_{s,\text{m}\text{i}\text{n}}$ check. Calculate $M_n.$

b$.$ Same cross section as part $($a$)$ but the steel is changed to four No$.10$ bars. Calculate $M_n.$ Calculate the percent increase in $M_n$ and $A_s.$

c$.$ Same cross section as part $($a$)$ but the depth $d$ is increased to $28$ in$.$ Calculate $M_m.$ Calculate the percent increase in $M_n$ and $d.$

d$.$ Same cross section as part $($a$)$ but $f_c$ is increased to $4000$ psi. Calculate $M_n.$ Calculate the percent increase in $M_n$ and $f_6.$

Practice Problems $-1$

$2-3.$ a$.$ Calculate the practical moment strength $M_n$ for a rectangular reinforced concrete cross section having a width $b$ of $13in.$ and an effective depth $d$ of $24$ in$.$ The tension reinforcing steel is four No$.8$ bars. $f_k^{\text{'}}-4000$ and $f_y+40,000.$

b$.$ Same as part $($a$)$ but $f_y=60,000.$ Also calculate the percent increase in $M_n$ and $f_y.$

$24.$ Determine $M_n$ for a reinforced concrete beam $16in.$ wide by $32$ in$.$ deep reinforced with seven No$.10$ bars $($placed in two layers: five in the bottom layer, two in the top layer, with I in$.$ clear between layers$).$ Use $f_s^{\text{'}}=4000$ and $f_y=60,000.$