SITUATION $9-$ igure PSM$1254$ shows a prestressed hallow core slab used for flooring of a library Given the following properties of the slab:

Area, $A=1\mathrm{.}5{10}^{5}m{m}^2$

Section modulus, $S_t=S_B=7\mathrm{.}2{10}^{6}m{m}^3$

$A=1\mathrm{.}20m$

$B=210mm$

Slab weight $=2\mathrm{.}8$kPa

Superimposed dead load $=2$kPa

Live load $=3\mathrm{.}2$kPa

Prestressing force $=860kN$ at $e=70mm$ below NA

The slab is simply supported on a span of $8m.$ Allowable stresses at service loads are $2\mathrm{.}9$MPa in tension and $15\mathrm{.}5$MPa in compression. Consider $15\%$ loss of prestress at service loads.

ralculate the following:

$25.$ The stress $($in MPa $)$ at the bottom fiber of the slab at the ends aue to initial prestress force.

A$.12\mathrm{.}6T$

B$.9\mathrm{.}5C$

C$.35T$

l$/14\mathrm{.}1$C

$52kN,$ find the maximum of boom.

the aliowable tension of ium value of $W.$

$26.$ The stress $($in MPa$)$ at the bottom fiber of the slab at midspan due to loads and prestress force.

A$.5\mathrm{.}81C$

B$.3\mathrm{.}62C$

C$.2\mathrm{.}361$

A$\mathrm{.}1$C

$27.$ The maximum total load $($in kN$/$m$)$ including its own weght. that the slab can be subjected to if the allowable stresses at service loads are not to be exceeded.

A$.15\mathrm{.}24$

$6.9\mathrm{.}58$

C$.1339$

$+379$