The long-term deflections of reinforced concrete members under sustained loads are mainly due to 1. differential shrinkage 2. creep under sustained loading 3. temperature effects Select the correct answer.
- A1 and 2 onlyCorrect
- B1 and 3 only
- C2 and 3 only
- D1, 2 and 3
Solution
Concept
Causes of long-term deflection
Step-by-step solution
1. Long-term deflection under sustained load arises mainly from creep and shrinkage (IS 456 Annex C). 2. Differential shrinkage between the tension and compression zones adds curvature. 3. Temperature effects are treated separately and are not the main cause.
Explanation
The deflection of an RC member grows with time because concrete creeps under sustained stress and shrinks differentially (more in the compression zone than near the steel).
Why the other options are wrong
Temperature effects are not counted among the principal causes, so options with statement 3 are not the best.
Shortcut
Long-term deflection = creep + shrinkage.
Common mistake
Including temperature.
Correct answer: A) 1 and 2 only