Q1: By over-reinforcing a beam, the moment of resistance can be increased not more than

ANS:D - 25%

1. Limitations of Over-Reinforcement: Over-reinforcing a beam involves adding more reinforcement than what is strictly necessary based on design calculations. This excess reinforcement increases the beam's capacity to resist bending moments beyond its original design specifications.
2. Increased Flexural Capacity: The additional reinforcement redistributes the internal stresses within the beam, effectively increasing its flexural capacity. This allows the beam to carry higher loads and resist larger bending moments without failure.
3. Economic Considerations: Over-reinforcing a beam can be a cost-effective solution in certain situations. It may allow for the use of smaller or lighter beams, leading to reduced material costs and construction time. However, it's essential to balance the potential cost savings with the structural integrity and performance of the beam.
4. Design Considerations: Structural design codes and standards typically provide guidelines on the maximum allowable percentage increase in moment of resistance through over-reinforcement. While over-reinforcement can enhance the beam's capacity, exceeding certain limits may compromise other aspects of the beam's behavior, such as ductility and crack control.
5. Safety and Durability: Excessive over-reinforcement can lead to brittle failure modes, reduced ductility, and inadequate crack control, posing safety risks and compromising the long-term durability of the structure. Therefore, it's crucial to exercise caution and adhere to design guidelines when considering over-reinforcement in beam design.

Given these considerations, a common guideline in structural engineering practice is to limit the increase in moment of resistance through over-reinforcement to approximately 25%. This ensures a reasonable balance between enhanced structural capacity and maintaining adequate structural performance, safety, and durability.