Understanding IS 800 Minimum Web Plate Thickness

The question asks about the minimum thickness requirement for unstiffened web plates used in steel structures, specifically referencing the Indian Standard code IS 800. The thickness is related to the clear distance between the flange angles.

IS 800 Specification for Unstiffened Webs

According to IS 800, which provides guidelines for the design of steel structures, specific provisions are made to ensure the stability and strength of components like web plates. For unstiffened webs, which are webs without intermediate stiffeners to resist buckling, a minimum thickness must be maintained.

Minimum Thickness Calculation

The code specifies that the minimum thickness of the web plate should not be less than a certain fraction of the clear distance between the flange angles. This minimum thickness helps prevent local buckling of the web under load.

The formula provided by IS 800 for the minimum thickness ($t_{w,min}$) of an unstiffened web plate is:

$$ t_{w,min} \ge \frac{d}{85} $$

Where:

• $t_{w,min}$ is the minimum required web plate thickness.
• $d$ represents the clear distance between the inner edges of the flange angles, measured parallel to the web.

Importance of Minimum Thickness

Maintaining this minimum thickness is crucial for the structural integrity of the member. It ensures that the web plate has sufficient slenderness ratio to resist buckling effects, especially when it is not reinforced with stiffeners. Failure to adhere to this minimum thickness could compromise the load-bearing capacity and stability of the steel component.

Conclusion

Therefore, based on IS 800 guidelines, the minimum thickness of an unstiffened web plate should not be less than $\frac{d}{85}$, where $d$ is the clear distance between the flange angles.