Question

 A simply supported prestressed beam of span 10 m is subjected to a point load of 10 kN at center. A prestressing force of 2000 kN is applied through the inclined tendon, Zero eccentricity at support, and ‘ e ’ at Midspan. To nullify the external point load effect, how much ‘ e ’ should be provided? Neglect the self-weight of the beam.

1. 12.5 mm
2. 50 mm
3. 70  mm
4. 85 mm

Answer 1

Correct Answer - Option 1 : 12.5 mm

Concept :

Prestressed beam:

Prestressed concrete is a form of concrete used in construction in a prestressed concrete member, the internal stresses are introduced in a planned manner, so That the stresses resulting from the superimposed loads are counteracted to the desired degree.

Eccentricity:

The degree to which two forms fail to share a common center; for example, in a pipe or tube whose inside is off–center Toth regard to the outside. the degree of eccentricity can be expressed by a plus or minus wall thickness tolerance.

Calculation:

Given ,

L=  10 m

w = 10 kN = 10 × 10³ N

P = 2000 kN = 2000 × 10³ N

We Know that,

\(P× e = \;\frac{{wl}}{4}\)

\(2000× 10^3× e = \;\frac{{10×10^3 × 10× 10^3}}{4}\)

e = 12.5 mm