The average permissible stress in bond for plain bars in tension isa)I...
Permissible Stress in Bond for Plain Bars
Permissible stress in bond for plain bars in tension is the maximum stress that can be applied to a bond between concrete and steel without causing failure. This stress is affected by various factors such as the type of concrete, diameter of the bar, and the amount of cover provided.
Effect of Compression on Permissible Stress
When a bar is in compression, the bond stress is reduced due to the development of radial cracks in the concrete. This reduces the effective contact area between the concrete and the steel, leading to a decrease in the permissible stress.
Options A, C, and D suggest a decrease in permissible stress when the bar is in compression, which is correct. However, option B suggests an increase in permissible stress, which is incorrect.
Correct Option: B
The correct answer is option B, which states that the permissible stress is increased by 25% for bars in compression. This increase in permissible stress is due to the development of hoop stresses in the steel, which counteract the reduction in bond stress caused by radial cracks in the concrete.
Conclusion
In conclusion, the permissible stress in bond for plain bars in tension is affected by various factors, including compression. When a bar is in compression, the permissible stress is reduced due to the development of radial cracks in the concrete. However, the development of hoop stresses in the steel counteracts this reduction, leading to an increase in permissible stress by 25%.
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