ANS:D - 1/7th of the span

Curtailing alternate bars at 1/7​th of the span in a simply supported slab is not a conventional practice in reinforced concrete construction. However, let's discuss the implications of this choice:

1. Limited Effectiveness: Curtailing alternate bars at 1/7th of the span may not provide sufficient reinforcement close to the supports where the bending moment is typically higher. This could result in inadequate reinforcement in critical regions, leading to increased risk of cracking and reduced structural performance.
2. Uneven Distribution: The distribution of reinforcement along the span of the slab would be uneven, with larger gaps between the reinforcement bars near the supports compared to the midspan region. This could lead to localized areas of higher tensile stresses and potential cracking.
3. Structural Integrity: In reinforced concrete design, it's crucial to ensure that the distribution of reinforcement is optimized to withstand the anticipated loads and minimize the risk of structural failure. Curtailing alternate bars at 1/7​th of the span may not provide the necessary reinforcement density to achieve this goal effectively.
4. Code Compliance: Design codes and standards typically provide guidelines for the spacing and detailing of reinforcement in concrete structures. While some flexibility may exist in certain cases, deviating significantly from established practices, such as 1/4​th or 1/5​th of the span, may not comply with these standards.

Overall, while it's essential to consider innovative solutions in structural design, curtailing alternate bars at 1/7​th of the span in a simply supported slab may not be advisable due to concerns regarding structural integrity, reinforcement distribution, and compliance with design standards.