As per IS 875 (Part 2) – 1987, what is the reduction in total distributed imposed load (in percent) for design of supporting structural elements in a structure with 10 floors ?
- A10%
- B20%
- C30%
- D40%Correct
Solution
Concept
Reduction in imposed floor loads for columns and foundations
Step-by-step solution
1. IS 875 Part 2 allows a reduction in the imposed load on columns, walls and foundations, depending on the number of floors carried. 2. Floors carried: 1 → 0%; 2 → 10%; 3 → 20%; 4 → 30%; 5 to 10 → 40%; more than 10 → 50%. 3. For 10 floors the reduction is 40%.
Explanation
The chance that all floors carry full imposed load at the same time falls with the number of floors, so the code allows a reduction. The reduction table stops increasing in steps of 10% at 4 floors and then gives 40% for 5 to 10 floors.
Why the other options are wrong
10%, 20% and 30% apply to 2, 3 and 4 floors.
Shortcut
Reduction steps: 0, 10, 20, 30, 40 (5–10 floors), 50 (>10).
Common mistake
Choosing 50%.
Correct answer: D) 40%