ANS:A - 1400 kg/cm²

To elaborate further on the correct value for the allowable tensile stress in mild steel stirrups used in reinforced cement concrete (R.C.C.) structures:

1. Material Properties:
   • Mild steel, also known as low carbon steel, is commonly used as reinforcement in concrete structures due to its favorable mechanical properties, including ductility, weldability, and moderate strength.
   • In R.C.C. construction, mild steel is often employed in the form of bars or wires for both longitudinal reinforcement (in beams and columns) and lateral reinforcement (in the form of stirrups or ties).
2. Allowable Stress:
   • The allowable tensile stress in mild steel stirrups is determined based on various factors, including material properties, design standards, and safety considerations.
   • The stress is typically limited to a certain value to ensure that the stirrups can safely withstand the applied loads without experiencing failure or excessive deformation.
   • The allowable stress is specified in units of force per unit area, commonly expressed in kilograms per square centimeter (kg/cm²) or megapascals (MPa).
3. Standard Values:
   • In accordance with standard engineering practices and design codes, the allowable tensile stress in mild steel stirrups for R.C.C. structures is typically around 230 kg/cm² or equivalent values in other units such as 23 MPa.
   • This value is based on empirical data, material testing, and considerations for structural safety and performance.
4. Design Considerations:
   • Engineers and designers select the appropriate size, spacing, and configuration of stirrups based on structural requirements, loading conditions, and design standards.
   • The design process involves determining the required amount of reinforcement to resist bending, shear, and other structural actions while ensuring that the stresses in the reinforcement do not exceed the allowable limits.
5. Quality Control:
   • During construction, it is essential to ensure that the specified grade of mild steel reinforcement is used and that the fabrication and installation of stirrups comply with the design specifications and applicable standards.
   • Quality control measures such as inspection, testing, and documentation help verify the integrity and performance of the reinforced concrete elements.

In summary, the allowable tensile stress in mild steel stirrups for R.C.C. structures is a critical parameter in structural design and construction, ensuring the safety, stability, and durability of the built environment. Engineers carefully consider this factor and adhere to established standards and best practices to achieve optimal performance and reliability in reinforced concrete structures.