What principles govern the classification of weld quality grades?
In the general notes of steel structure construction drawings, have you ever written a line like this: “Drafted, stamped, and issued.” Everything seems to flow smoothly. “For this project, Grade 1 welds shall undergo 100% non-destructive testing, Grade 2 welds shall be subject to 20% sampling inspection, and Grade 3 welds shall undergo visual inspection.” However, if someone were to ask at this moment, “Why must this weld be Grade 1, while that one can be Grade 2? Who exactly determines this ‘grade’?” would your answer still flow so smoothly? This question, though seemingly basic, represents the most fundamental—and yet most easily overlooked—underlying logic in steel structure welding design. The classification of weld quality grades is by no means arbitrary, nor is it a matter of the designer’s “whim.” It is underpinned by a clear, rigorous set of principles, proven through engineering practice, which directly determine the structural safety and service life of the structure. T...