To construct the deck of a bridge over a deep ravine, steel beams spaced at $2\mathrm{.}4$ m on centers, and simply supported on a span of $20$ m$,$ are used to support the construction loads which include temporary formwork and construction live loads equivalent to $4200$ Pa$.$ At this stage, only the steel beams carry the loads. After the slab has hardened, sufficient shear connectors welded to the beam flange provide full composite action of the steel beam with the $0\mathrm{.}15$ m thick cast$-$ in$-$place concrete slab.

Given:

Concrete, fc $=20\mathrm{.}7$ MPa

Concrete unit weight $=24$ kN$/$m$^3$

Steel, Fy $=345$ MPa

Modular ratio, n $=9$

For composite action, use $1\mathrm{.}8$ m flange width.

Properties of the steel beam:

Section W$685$ mm x $152$ kg$/$m

tw $=13$ mm

bf $=250$ mm

d $=688$ m

Ix $=15$x$10^8$ mm$^4$

tf $=21$ mm

Iy $=0\mathrm{.}58$x$10^8$ mm$^4$

A $=19355$ mm$2$

$1.$Determine the maximum bending stress $($MPa$)$ in the beam due to dead load which include beam weight, slab and wearing surface of $600$ Pascals and the construction loads.

$2.$Determine the maximum tensile stress $($MPa$)$ in the beam due to standard truck load $($H load$)$ alone consisting of $15\mathrm{.}2$ kN front wheel load and $61\mathrm{.}8$ kN rear wheel load. Distance wheel loads is $4\mathrm{.}27$ m$.$ Include $24\%$ impact on live load.

$3.$ Determine the maximum compressive stress $($MPa$)$ in the concrete slab.

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