Reinforced Concrete Footing on Piles

Introduction
According to IS 456 - 1978 (Indian Standard Code of Practice for Plain and Reinforced Concrete), the thickness of reinforced concrete footings on piles at its edge is kept less than 15 cm.

Reasoning
The reason for keeping the thickness of the reinforced concrete footing on piles at its edge less than 15 cm is to ensure proper load distribution and stability. The thickness of the footing is directly related to the load it can carry and the stability it can provide.

Load Distribution
The load from the superstructure is transferred to the piles through the footing. The thickness of the footing plays a crucial role in distributing the load evenly to the piles. A thicker footing will distribute the load over a wider area, reducing the load-bearing capacity of each pile. On the other hand, a thinner footing concentrates the load on a smaller area, increasing the load-bearing capacity of each pile.

Stability
The stability of the footing is also a critical factor. A thicker footing increases the lever arm between the applied load and the pile, resulting in a larger overturning moment. This can lead to instability and potential failure of the footing-pile system. By keeping the thickness of the footing less than 15 cm, the overturning moment is minimized, ensuring the stability of the system.

Considerations
While the IS 456 - 1978 recommends a maximum thickness of 15 cm for reinforced concrete footings on piles, it is important to note that this is a general guideline. The actual thickness may vary depending on the specific design requirements, soil conditions, and structural loads. It is essential to consult the relevant design codes and guidelines, conduct proper structural analysis, and consider site-specific factors before finalizing the thickness of the footing.

Conclusion
To ensure proper load distribution and stability, the thickness of reinforced concrete footings on piles at its edge is recommended to be less than 15 cm according to IS 456 - 1978. This guideline helps in optimizing the load-bearing capacity of each pile and minimizing the overturning moment, thereby ensuring the overall stability of the footing-pile system. However, it is important to consider other design factors and site-specific conditions before finalizing the thickness of the footing.