Minimum reinforcement in slabs in each direction Specify the minimum steel area in either direction as a percentage of the gross concrete section of the slab.
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A0.75%
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B0.10%
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C0.15%
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D0.20%
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E0.12%
Answer
Correct Answer: 0.15%
Explanation
Introduction:Minimum reinforcement controls cracking from shrinkage and temperature and ensures ductility even when applied loads are low. The requirement applies in each orthogonal direction of a reinforced concrete slab.
Given Data / Assumptions:
- Reinforced concrete slab with deformed (or mild) bars.
- Percentage calculated on gross concrete cross section.
Concept / Approach:
Typical code provisions specify minimum percentages. For slabs with mild steel, 0.15% is a common minimum; for high strength deformed bars, 0.12% may be permitted. The question asks for a conservative minimum figure suitable across cases.
Step-by-Step Solution:
1) Identify minimum in either direction of slab.2) Adopt 0.15% as a safe minimum applicable to mild steel and acceptable as a conservative choice more generally.3) Ensure spacing and bar diameters also satisfy crack control.Verification / Alternative check:
Check against bar spacing limits and cover; sometimes 0.12% is permitted with HYSD, but 0.15% remains a safe baseline.
Why Other Options Are Wrong:
0.75% is excessive for minimum steel; 0.10% and 0.12% can be insufficient or code-restricted depending on bar type; 0.20% is not the standard minimum.
Common Pitfalls:
Providing minimum percentage but violating maximum spacing; using large diameter bars at very wide spacing, which is less effective for crack control.
Final Answer:
0.15%