Situation $2$: A prestressed concrete beam has a width of $300$

$mm$ and overall depth of $600mm.$ The prestressing tendons

are placed a distance $"e"$ below the neutral axis of the beam

and the applied prestressing force is $P=1500kN.$ There is a

$15\%$ loss of prestress.

Determine the compressive stress in the concrete when $P$

is applied at the centroid of the beam. Ans: $-7\mathrm{.}08$MPa

What is the maximum compressive stress in the beam

when $e=120mm?-15\mathrm{.}58$MPa

Determine the eccentricity $"e"$ such that no tension will

occur at the top fiber of the beam. Ans: $100mm$

If the beam has a simple span of $5m$ carrying a load of

$20k\frac{N}{m},$ determine the stress in the concrete at the level

of the tendons at supports when $e=120mm.$ Ans : $10\mathrm{.}48$MPa