ANS:C - 30

the maximum ratio of span to depth of a simply supported slab spanning in one direction is generally considered to be around 20. This is a typical guideline in structural engineering practice and design codes. Let's delve into why this ratio is significant:

1. Deflection Control: One of the primary considerations in slab design is controlling deflections to ensure serviceability and user comfort. A higher span-to-depth ratio tends to lead to increased deflections under service loads. Keeping the span-to-depth ratio within an appropriate range helps limit deflections to acceptable levels.
2. Stiffness: A lower span-to-depth ratio generally results in a stiffer slab, which is beneficial for minimizing deflections and improving the overall structural performance. Stiffer slabs are less prone to excessive cracking and are better able to distribute loads efficiently.
3. Crack Control: Excessive deflections in slabs can lead to increased cracking, particularly at mid-span sections. By keeping the span-to-depth ratio within a reasonable range, the likelihood of excessive cracking is reduced, contributing to the durability and aesthetics of the structure.
4. Construction Considerations: A lower span-to-depth ratio may also simplify construction by allowing for easier formwork installation, concrete placement, and finishing. It may also result in more economical designs by reducing the amount of concrete and reinforcement required.

While the exact maximum ratio of span to depth can vary depending on specific project requirements, loading conditions, and design codes, a common guideline is to aim for a ratio around 20 for simply supported slabs spanning in one direction. This guideline helps balance structural performance, serviceability, and construction considerations in slab design.