Q1: The diameter of longitudinal bars of a column should never be less than

ANS:D - 12 mm

The diameter of longitudinal bars (also known as main reinforcement) of a column is a critical aspect of structural design, ensuring that the column can adequately resist the applied loads and maintain structural stability. The diameter of these bars is typically determined based on structural requirements and design standards. According to common structural design practices and codes such as ACI (American Concrete Institute) and Eurocodes, the minimum diameter of longitudinal bars for columns is usually specified to ensure sufficient strength, ductility, and constructability. This minimum diameter requirement helps to prevent issues such as inadequate load-bearing capacity, insufficient bond strength, and difficulties during construction. While specific design requirements may vary depending on factors such as column size, height, and loading conditions, a commonly accepted minimum diameter for longitudinal bars of columns is typically 12 mm. This diameter provides adequate strength and stiffness to resist the applied loads and ensures proper bond with the concrete. Therefore, the correct answer to the question "The diameter of longitudinal bars of a column should never be less than" is: 12 mm This ensures that the column meets structural safety and performance criteria, providing sufficient strength and durability over its service life.