Elastic Design for flexure
Max. pre-stressing force is limited by
1. Tension at top - f tt during transfer - Eq.1
2. Min. Comp stress at bottom - f tw during working load - Eq.4
Therefore from Eq.1 and Eq.2 and taking
When MG is large as will be the case for long span and/or heavy girders, the computed eccentricity e from Eq.10, may fall below the bottom of the beam. In that case, the e available is worked out and Fi is increased suitably.
Fi for know eccentricity e working load is:
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