The correct answer is: A. 0.7
The ratio of the end and intermediate spans is kept at 0.7 to ensure that the floor slab is evenly supported. If the ratio is too high, the end spans will be overloaded and may crack. If the ratio is too low, the intermediate spans will be overloaded and may crack.
The ratio of the end and intermediate spans is calculated by dividing the length of the end span by the length of the intermediate span. For example, if the length of the end span is 10 feet and the length of the intermediate span is 15 feet, the ratio is 0.67.
The ratio of the end and intermediate spans is an important factor in the design of a floor slab. It is important to choose a ratio that will ensure that the floor slab is evenly supported and will not crack.
Here is a brief explanation of each option:
- Option A: 0.7. This is the correct answer. The ratio of the end and intermediate spans is kept at 0.7 to ensure that the floor slab is evenly supported.
- Option B: 0.8. This is a higher ratio than the recommended ratio of 0.7. If the ratio is too high, the end spans will be overloaded and may crack.
- Option C: 0.9. This is an even higher ratio than option B. If the ratio is too high, the end spans will be overloaded and may crack.
- Option D: 0.6. This is a lower ratio than the recommended ratio of 0.7. If the ratio is too low, the intermediate spans will be overloaded and may crack.