Which of the following statements are correct? i. Pre-tensioning system has greater certainty about its durability ii. For heavy loads and large spans in buildings or bridges, post tensioning system is cheaper than pre-tensioning system iii. The loss of prestress is less in pre-tensioning system than in post-tensioning system
- AOnly (i)
- B(i) and (ii)Correct
- C(ii) and (iii)
- D(i), (ii) and (iii)
Solution
Concept
Comparison of the two prestressing systems
Step-by-step solution
1. Pre-tensioning gives bond over the whole length with reliable durability (i). 2. For heavy loads and long spans post-tensioning is cheaper (ii). 3. The loss of prestress is generally larger in pre-tensioning (elastic shortening in all tendons), so (iii) is incorrect.
Explanation
Only (i) and (ii) are correct.
Why the other options are wrong
Options with (iii) wrongly say pre-tensioning loses less.
Correct answer: B) (i) and (ii)