As per IS:1904-2021, wind or seismic load may be neglected in design of foundations when it is
- Aless than 10% of dead load and live loads
- Bless than two-third of dead load and live loads
- Cless than 50% of dead load and live loads
- Dless than 25% of dead load and live loadsCorrect
Solution
Concept
Neglecting wind or seismic loads in foundation design when they contribute a minor portion (less than 25%) of the total vertical dead and live load.
Step-by-step solution
1. Refer to IS 1904:2021 (or earlier revisions like IS 1904:1986 clause on design loads). 2. Check the provision regarding wind and seismic forces. 3. The code specifies that wind or seismic forces can be ignored if they do not exceed 25% of the dead and live loads.
Explanation
According to IS 1904 (Code of Practice for Design and Construction of Foundations in Soils: General Requirements), wind or seismic loads may be neglected in the design of foundations when such loads are less than 25% of the combined dead and live loads.
Why the other options are wrong
A: 10% is too low and not specified by the code for this provision. B: Two-third (66%) is much higher than the code threshold. C: 50% is incorrect; wind/seismic loads exceeding 25% must be considered.
Shortcut
Remember the 25% threshold for wind/seismic loads in standard foundation codes.
Common mistake
Confusing 25% with 10% or 50% which are common distractors in code-based questions.
Correct answer: D) less than 25% of dead load and live loads