As per Indian standard code of practice for prestressed concrete $$(IS:1343-1980)$$ the minimum grades of concrete to be used for post-tensioned and pre-tensioned structural elements are respectively

Let $$jd$$ be the lever arm between the resultant tensile force $$T$$ in the reinforcing prestressing steel and the resultant compressive force $$C$$ in concrete of a reinforced / prestressed concrete beam. When subjected to increase in the external bending moment, which one of the following statements is true in reinforced and prestressed concrete beams?

In reinforced concrete beams

Let $$jd$$ be the lever arm between the resultant tensile force $$T$$ in the reinforcing prestressing steel and the resultant compressive force $$C$$ in concrete of a reinforced / prestressed concrete beam. When subjected to increase in the external bending moment, which one of the following statements is true in reinforced and prestressed concrete beams?

In prestressed concrete beams

A uniformly distributed load intensity, $$w$$ acting on a simply supported prestressed concrete beam of span $$L,$$ producing a bending moment $$M,$$ at mid-span is to be balanced by a parabolic tendon with zero eccentricity at ends and eccentricity $$e,$$ at mid-span. The prestressing force required depends on