Rebar detailing in tension zones: Lapped splices in tensile reinforcement are generally avoided for bars larger than which nominal diameter, as per common RC detailing practice (e.g., IS 456 recommendations)?

Introduction / Context:
Lapped splices transfer force via bond between overlapping bars. In high-tension zones with large bar diameters, long lap lengths and heavy congestion can compromise constructability and quality. Design codes therefore discourage laps for large-diameter tension bars and recommend welded or mechanical splices instead.

Given Data / Assumptions:

• Tension reinforcement (not compression).
• Nominal bar diameters following standard metric sizes.
• General practice aligned with IS 456 recommendations.

Concept / Approach:
For tension bars greater than a code-specified cutoff diameter, lap splicing is generally not preferred. For IS 456, this practical limit is 36 mm for tension bars. Beyond this, welding or mechanical couplers are recommended to ensure reliable force transfer and reduce congestion.

Step-by-Step Reasoning:
Identify that the context is tensile laps, not compression.Recall the recommended maximum bar diameter for lapping in tension (≈ 36 mm).Conclude that for bars larger than 36 mm, avoid lap splicing and adopt welded/mechanical splices.

Verification / Alternative check:
Project specifications often reiterate this practice because couplers improve site handling, reduce reinforcement congestion, and enhance quality control in highly stressed regions.

Why Other Options Are Wrong:
18/24/30/32 mm: Commonly lapped in practice; no general code prohibition for these diameters.

Common Pitfalls:

• Using long laps for 40 mm bars in tension zones, causing congestion and poor compaction.
• Not verifying the splice location (avoid peak moment regions).

Final Answer:
36 mm diameter