Limit State Method for Design of Steel Structures as per IS Code

The design of steel structures is governed by the Indian Standard Code IS 800:2007. As per this code, the Limit State Method is mainly adopted for the design of steel structures. Let us understand this method in detail.

What is the Limit State Method?

The Limit State Method is a design philosophy that considers the structure's behavior at the ultimate limit state and the serviceability limit state. The ultimate limit state is the state where the structure collapses, while the serviceability limit state is the state where the structure performs its intended function without any significant deflection or deformation.

The Limit State Method considers the following limit states:

- Ultimate Limit State (ULS)
- Serviceability Limit State (SLS)

Design Criteria as per Limit State Method

The design of steel structures as per IS 800:2007 is based on the following design criteria:

- Limit States: The design should satisfy the limit states of strength, stability, and serviceability.
- Safety Factors: The design should ensure adequate safety against failure due to overloading, buckling, or any other cause.
- Load Combinations: The design should consider various load combinations as per the code to ensure adequate safety and serviceability.
- Ductility: The design should ensure adequate ductility in the structure to withstand the effects of earthquake loads.
- Fatigue: The design should consider the fatigue effects due to repetitive loads, which may cause failure in the long run.

Advantages of Limit State Method

- The Limit State Method provides better safety against failure than the Working Stress Method.
- It considers the ultimate limit state and the serviceability limit state, which ensures that the structure performs its intended function without any significant deflection or deformation.
- It considers different load combinations, which ensures that the structure remains safe and serviceable under all possible loading conditions.

Conclusion

The Limit State Method is the most widely adopted method for the design of steel structures as per the Indian Standard Code IS 800:2007. This method ensures the safety and serviceability of the structure and considers various load combinations and limit states.