Consider the $53321082$ UKB steel grade S$275$ simply supported composite beam shown in figure Q$4.$ The beam supports a general office use composite floor slab with a steel decking of $0\mathrm{.}9mm$ Tata CF$60.$The depth of the concrete above deck profile is $70mm$ and depth of deck profile is $60mm$ as shown in figure Q$4($b$).$ The beam is subjected to a

uniformly distributed variable actions made from imposed floor load, qk$1=2\mathrm{.}5$kN$/$m$2$ and allowance for movable partitions of $qk,2=0\mathrm{.}9k\frac{N}{m}2$

Calculate the fire proofing critical temperature for the composite beam that need to be supplied to a fire protection manufacturer and comments on your findings.

Given the followings:

MRd $=907\mathrm{.}40kNm($design value of the moment resistance of the composite section at

room temperature$)$

Ceiling and services $=0\mathrm{.}70$kN$/$m$2,$

$0\mathrm{.}9mm$ Tata CF$60,$

with self$-$weight $=0\mathrm{.}1$kN$/$m$2$

$1\mathrm{.}1=0\mathrm{.}5$ General office use

Shear connectors

Connector diameter, $d=20mm,$ Overall height, $hsc=90mm$

Ultimate tensile strength, fu $=450\frac{N}{m}m2$

One shear connectorper rib, Studs are located at $250mm$ centres of ribs of steel duck

$kt=$ reduction factor $=0\mathrm{.}85$ Concrete Normal weight grade C$30/35,$

Slab self$-$weight $=2\mathrm{.}43k\frac{N}{m}2,$Ecm$=31k\frac{N}{m}2$