In foundation design, why is a column footing provided beneath a vertical column?
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ATo spread the column load over a larger area of soil
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BTo ensure the bearing pressure on soil remains within permissible limits
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CTo distribute column load uniformly through the footing to the ground
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DAll of the above
Answer
Correct Answer: All of the above
Explanation
Introduction / Context:Footings are shallow foundations that transfer column loads safely to the soil. Their sizing and detailing are central to geotechnical and structural performance.
Given Data / Assumptions:
- Vertical column carrying axial load (and possibly moments).
- Soil has a safe bearing capacity (SBC) that must not be exceeded.
Concept / Approach:Adequate footing area keeps contact pressure compressive and ≤ SBC, while reinforcement and geometry spread and deliver the load to the soil without excessive settlement or shear failure.
Step-by-Step Solution:Compute required area A ≈ Load / SBC.Detail reinforcement to distribute load to soil and control cracking.Check punching shear, one-way shear, and bending.
Verification / Alternative check:Soil mechanics and IS codes align: increasing footing area reduces pressure and settlements for a given load.
Why Other Options Are Wrong:
- Each of A, B, C is individually true; only D captures the full purpose.
Common Pitfalls:Ignoring differential settlement, eccentric loading, or groundwater effects.
Final Answer:All of the above