What is the minimum size fillet weld requirement for cyclically loaded structures?

The minimum size fillet weld requirement for cyclically loaded structures is specified as 3/16 inch. This requirement is important because cyclic loading, which involves repeated loading and unloading, can lead to fatigue failure in welded connections. The 3/16 inch size ensures that the weld is sufficiently robust to withstand the stress associated with these repeated loads while maintaining the integrity and longevity of the structural element.

Choosing a weld size that is too small may not provide adequate strength or resistance to fatigue, which could result in premature failure of the joint. Therefore, the code establishes 3/16 inch as the minimum size to enhance the durability of the weld in service conditions where cyclic loading is a consideration. This decision aligns with best practices in welding engineering that prioritize both structural safety and performance under variable loading conditions.