Explanation :
Download UDL w=6 kN/m
Efficentricity, e = 50 mm
Prestressing force, P = 200 kN
EI = 2 x 10^{4} kN m^{2}
L = 6 m
Rotation due to presents $ =\frac{\mathrm{Pel}}{2\mathrm{EI}} $
$ \begin{array}{l}=\frac{200\times50\times10^{-3}\times6}{2\times2\times10^4}=1.5\times10^3\\\end{array} $
Rotation due to UDL = $ \frac{\mathrm{wL}^3}{24\mathrm{EI}} $
$ =\frac{6\times(6)^3}{24\times2\times10^4}=2.7\times10^{-3} $
Net Rotation $ =2.7\times10^{-3}-1.5\times10^{-3} $
$ =1.2\times10^{-3} $ radian
Elongation of the cable $ =2\times50\times1.2\times10^{-3} $
= 0.120 mm