Question

A timber beam of 100 mm width and 200 mm depth is reinforced with two steel plates of 100 mm width and 5 mm thickness as shown in figure-I and figure-II


Which one of the following statements is correct for the same value of bending stress in the timber ?

• A. Moment of resistance in figure-I will be more than that in figure-II.
• B. Moment of resistance in figure-II will be more than that in figure-I.
• C. Moment of resistance in figure -I will be equal to that in figure-II.
• D. No logical comparison can be made.

Answer 1

The correct option is A Moment of resistance in figure-I will be more than that in figure-II.

For the same value of bending stress in timber, moment capacity of timber is same in both cases. In figure-I steel plates are away from the NA so more stress is generated in steel plates due to more strain. As they are away so lever arm is also large. Hence moment of resistance is more in figure-I.