Picture it$.$ It$$s $5$ o$$clock on Friday and at the end of a long week all Dave wants to do is go home. But

his boss has other ideas; he tells Dave that he can go once he has designed the tension

reinforcement for the beam in Figure $2.$

a$)$ Design reinforcement for this beam and check its suitability

b$)$ If the length of the beam is reduced to $7$m$,$ can the amount of reinforcement also be

reduced? If so$,$ what is a sensible amount of reinforcement?

c$)$ Redesign the beam If the beam is to be kept at $12$m span, and the depth to the neutral axis

is to be limited to x$/$d $=0\mathrm{.}45$

Points to consider:

$$ Are you designing the beam for the serviceability or ultimate load? Why?

$$ Could other diameter bars have been used? How would this affect the beam?

$$ What other factors will affect the amount of longitudinal reinforcement in the beam?

Figure $2$

Design Data:

$$ Grade of steel, fyk $=500$MPa

$$ Grade of concrete, fck $=30$MPa

$$ Dead load $($incl$.$ self$-$weight of beam$)=10$kN$/$m

$$ Imposed load $=5$kN$/$m

$$ Overall cross$-$section of the beam $=550$ x $250$mm

$$ Dry or low air$-$humidity conditions

$$ Cover $=25$mm