For the beam section shown:

$1-$ Find Mer

$2-$Find cracked moment of inertia

$3-$ Find ultimate moment strength

$4-$Describe type of failure

$F^{\text{'}}c=30$mpa

$Fy=280$Mpa

$EC=4700\sqrt[\phantom{2}]{F^{\text{'}}C}$

$n=\frac{Es}{Ec}$

$=\frac{As}{bd}$

$P_b=0\mathrm{.}85\frac{{}_{1}Ftc}{Fy}[\frac{600}{600+Fy}]$ cover to center

$C=0\mathrm{.}85F^{\text{'}}$cab of steel $40$ mm

$a=1c$

$T=$AsFy

$0\mathrm{.}851=0\mathrm{.}85-0\mathrm{.}008(fc-30$MPa$)0\mathrm{.}65$

$Mn=C(d-\frac{a}{2})$

$Mn=T(d-\frac{a}{2})$

$4$ bars $25$ mm diameter