Problem $2.$

For the rectangular beam shown here, calculate the development lengths of top No$.7$ bars and bottom No$.9$ bars. No$.4$ bars are used for stirrups. The spacing of stirrups is $6$ in$.$ The clear side cover depth is $1\mathrm{.}5$ inch. $($Clear cover depth means the distance from the beam face to the outer surface of a bar$).$

Normalweight concrete is used.

$f_c^{\text{'}}=4000$ psi, $f_y=f_{yt}=60000$ psi.

Equation $(6\mathrm{.}5)$ and $(6\mathrm{.}6)$ will be used respectively. And the results shall be compared.

$2.$ From the conditions given in problem $1,$ the yield stresses $f_y$ and $f_{yt}$ have been increased to $80000$ psi psi, and $f_y=f_{yt}=80000$ psi$).$ Determine the development lengths with the increased yield strength.

$3.$ From the conditions given in problem $1,$ only the yield stress $f_c^{\text{'}}$ has been increased to $8000$ psi