Question

The prestressing force in the tendon is 1200 kN, acting on a beam section of 400 mm $\times$ 600 mm. Span of the beam is 6 m and carries an all inclusive load of 40 kN/m. If the profile of the beam is as per load balancing cable for the beam then the cable should be provided with a central dip of _____ mm.

• A. 150

Answer 1

The correct option is A 150
Upward pressure provided by the parabolic cable is given by

$=\frac{8Pe}{l^2}=\frac{8\times 1200\times e}{6^2}$

$=\frac{800e}{3}kN/m$

This upward pressure should fully balance the external loading thus

$\frac{800\times e}{3}=40$

$\therefore e=\frac{40\times 3}{800}=0.15m$

i.e., $=150mm$