Reinforcement in beams - Choice of reinforcement type and arrangement

The correct answer for this question is option 'C', which states that bars may be arranged singly, or in pairs in contact, or in groups of three or four bars bundled in contact. Let's analyze why this is the correct choice and understand the reasons behind it.

Different type and grade for main reinforcement:
This option is not recommended because using different types and grades of steel for main reinforcement can lead to unequal strength and performance. It is essential to maintain uniformity in the type and grade of reinforcement used in the main reinforcement to ensure consistent structural behavior and load distribution.

Same grade for secondary reinforcement:
Option 'B' suggests that secondary reinforcement should be of the same grade of steel as used in the main reinforcement. This is a valid consideration as it helps maintain compatibility between the main and secondary reinforcement, ensuring similar characteristics and behavior under load. Using different grades may result in differential behavior, which can adversely affect the structural integrity.

Arrangement of bars:
Option 'C' suggests that bars can be arranged singly, in pairs in contact, or in groups of three or four bars bundled in contact. This option is preferred because it provides flexibility in the arrangement, allowing engineers to tailor the reinforcement design according to specific structural requirements.

- Singly arranged bars: This arrangement is suitable for small beams or where the load is relatively low. It is commonly used when the beam's width is limited, and multiple bars cannot be accommodated.

- Pairs in contact: This arrangement is beneficial for larger beams or when higher loads need to be supported. Placing two bars side by side allows for increased load-carrying capacity and improved structural performance.

- Bundled bars: This arrangement involves grouping three or four bars together in contact. It provides even greater load-carrying capacity and stiffness than the previous arrangements. Bundling bars is typically done for larger diameter bars (greater than 40 mm) to facilitate ease of handling and placement.

Bundling of bars:
Option 'D' states that bars larger than 40 mm diameter should be bundled, except in columns. This is a common practice as larger diameter bars are more challenging to handle and place individually. Bundling them together simplifies the construction process while maintaining the required level of reinforcement.

In conclusion, the correct choice for reinforcement in beams is option 'C', which allows for various arrangements of bars depending on the beam's size, load, and structural requirements. It is essential to maintain uniformity in the type and grade of reinforcement used in the main reinforcement and ensure compatibility between the main and secondary reinforcement. Additionally, bundling bars larger than 40 mm diameter is a common practice to facilitate construction.