Correct Answer - Option 3 : 76%
- As per CI. 18.5.1 of IS 1343 at the time of initial tensing, the maximum tensile stress immediately behind the anchorages shall not exceed 80% of the ultimate tensile strength of wire or bar or strand.
As per the given option, we should take 76% (for the safer side)
- Grade of concrete:
M 40 for pre-tensioned members
M 30 for post-tensioned members