In reinforced concrete beam design, the maximum area of compression reinforcement permitted in a rectangular section of size B × D is limited to what fraction of the gross area BD?

Introduction / Context:
Limiting the quantity of steel in beams avoids congestion, ensures proper compaction of concrete, and preserves ductile behavior. While tension steel often governs, compression reinforcement is also restricted by code to maintain constructability and reliable strain compatibility. This question asks for the maximum permissible area of compression steel as a fraction of the gross concrete area BD for a rectangular beam section.

Given Data / Assumptions:

• Section: rectangular beam with breadth B and overall depth D.
• Quantity: maximum compression reinforcement area relative to gross area BD.
• Normal reinforced concrete beam design context; no special confinement provisions.

Concept / Approach:
Codes cap the total steel percentage in a beam to avoid over-reinforcement and brittle compression failures. A common upper bound used in exam literature is 4% of the gross cross-sectional area. Staying within this limit typically ensures that the neutral axis does not shift excessively and that the section can develop adequate rotation capacity at ultimate loads.

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