A pre-stressed concrete simply supported rectangular beam is having 'A' cross-sectional area has a span 'S' and is subjected to a bending moment 'M' at mid span sections. The pre-stressing tendons are located at an eccentricity 'e' from the centroidal axis provide an effective pre-stress of 'P'. The extreme bottom fibre stress at mid-span section is given as
1
\(\frac{P}{A}-\frac{P e}{Z_{b}}+\frac{M}{Z_{b}}\)
2
\(\frac{P}{A}+\frac{P_{e}}{Z_{b}}-\frac{M}{Z_{b}}\)
3
\(\frac{P}{A}+\frac{P e}{Z_{b}}+\frac{M}{2 Z_{b}}\)
4
\(\frac{P}{A}-\frac{P_{e}}{Z_{b}}-\frac{M}{Z_{b}}\)