Explanation:
In the limit state approach, the spacing of main reinforcement controls primarily the cracking of the structure.

Factors affecting cracking:
There are various factors that affect the cracking of the reinforced concrete structure. Some of the significant factors are as follows:

1. Tensile strength of concrete
2. Bond strength between concrete and reinforcement
3. Reinforcement percentage
4. Spacing of reinforcement
5. Load on the structure

Spacing of reinforcement:
The spacing of main reinforcement is one of the critical factors that affect the cracking of the reinforced concrete structure. If the spacing of the reinforcement is more than the specified limit, it may result in excessive deflection and cracking of the structure. The main reinforcement helps to resist the tensile stresses in the structure. If the spacing is too much, the reinforcement may not be able to resist the tensile stresses, and it may result in cracking.

Limit state approach:
In the limit state approach, the ultimate limit state (ULS) and the serviceability limit state (SLS) are considered. The ULS is the state in which the structure collapses, while the SLS is the state in which the structure performs its intended function without excessive deflection or cracking.

Conclusion:
In conclusion, the spacing of main reinforcement primarily controls the cracking of the reinforced concrete structure in the limit state approach. Therefore, it is essential to maintain the specified spacing of reinforcement to ensure the safety and serviceability of the structure.

Cracking