$(5)$ Problem $4,$ Chapter $16$

A post$-$tensioned beam is to be designed to carry, in addition to its self$-$weight, a

uniformly distributed live load of $13\mathrm{.}5k\frac{N}{m}$ over its entire simply supported span

of $18$ m $.$ Assume a minimum cover of $100$ mm $($to $H).c=15$MPa,$c_1=0.=0\mathrm{.}85,$

$=2400k\frac{g}{m^1}$ and use the critical stress state $($CSS$)$ approach to

$($a$)$ obtain a sultable cross$-$sectlon

$($b$)$ compute the minimum required prestressing force $H$ and the $c_B$ at midspan.

Notes:

You are required to use one of the Standard precast $1-$girder sections detailed

in Figure C$(1)$ in Appendix C$.$

A design with an oversiged section is not acceptable.