In post-tensioning, the tensioning of the steel tendons is performed
- ABefore the concrete is poured into the formwork.
- BSimultaneously while the concrete is being vibrated.
- CAfter the concrete has hardened and achieved sufficient strength.Correct
- DOnly when the structure is subjected to its full live load.
Solution
Concept
Post-Tensioned Concrete
Formula
N/A
Step-by-step solution
1. Identify the process of post-tensioning in prestressed concrete. 2. Recall that in post-tensioning, steel tendons are tensioned after the concrete has hardened and gained sufficient strength. 3. Compare with the given options and select Option (c) as the correct choice.
Explanation
In post-tensioning, concrete is poured first and allowed to harden and gain strength. Once the concrete is strong enough to handle the stress, high-strength steel cables (tendons) placed inside ducts are pulled or tensioned using heavy jacks and anchored at the ends. This places the hardened concrete under compression, making the structure much stronger and resistant to heavy loads.
Shortcut
To remember the difference between Pre-tensioning and Post-tensioning, use the simple prefix rule: - Pre-tensioning: "Pre" means BEFORE (tendons are tensioned before concrete is poured). - Post-tensioning: "Post" means AFTER (tendons are tensioned after concrete hardens).
Common mistake
A common mistake is selecting Option A by confusing post-tensioning with pre-tensioning, where tendons are tensioned before the concrete is poured. In post-tensioning, the concrete must be poured, hardened, and reach sufficient strength before tensioning can occur.
Correct answer: C) After the concrete has hardened and achieved sufficient strength.