IS 456 limit — maximum percentage of tension reinforcement permitted in RCC beams (as a percentage of cross-sectional area) is:

Introduction / Context:
Codes limit maximum tensile reinforcement to ensure ductile behavior and proper concrete compaction around bars. Excessive steel leads to congestion, poor bond, and brittle failures. IS 456 specifies an upper cap for tension steel in beams, widely asked in MCQs.

Given Data / Assumptions:

• RCC rectangular/singly reinforced beams per IS 456.
• Percentage is of gross cross-sectional area b*d (effective considerations for detailing aside).

Concept / Approach:

IS 456 restricts the maximum area of tension reinforcement in a beam to 4% of the cross-sectional area to maintain ductility and constructability. Typical economical reinforcement ratios are far lower, but this cap prevents over-reinforcement and brittle tension failures.

Step-by-Step Solution:

Verification / Alternative check (if short method exists):

Design handbooks and code summaries list 4% as the limit; good practice is usually below 2–3% for congestion control.

Why Other Options Are Wrong:

0.15% and 1% are closer to minimums/nominal limits in other contexts; 1.5% is not the maximum; 6% exceeds the code cap.

Common Pitfalls (misconceptions, mistakes):

Confusing minimum and maximum percentages; overlooking constructability when approaching the upper limit.

Final Answer:

4%