The design yield strength is the yield strength according to the material grade as defined in Table 6 of BS5950:Part1:1990 and Table 9 of BS5950:Part1:2000. To assign a grade to a section the engineer assigns a nominal yield strength (py) to the column section. Based on the magnitude of the nominal yield strength the section is assigned a grade from the table 6 (1990) or 9(2000). If the nominal yield strength is within a range of yield strengths indicated in the table then the associated grade is assigned to the section and the rules relating material thickness to design yield strength are followed. If the nominal yield strength is not within a range of yield strengths indicated in the table then the design yield strength is assigned the nominal yield strength value, and no reduction is made for material thickness. The design yield strength will never be larger than the engineer provided nominal yield strength.