Re: 4.3.4.5. control The purpose of article 4.3.4.5 is so that the bulkheads do not carry more than 75% of the load in wall + frame systems with high ductility level (A14 or A15). Because if the curtains carry more than this ratio, it is less ductile than the A14 or A15 system. Therefore, the R value should be reduced. In the sentence I marked with yellow color in the image below, it says, if this ratio is not met, consider the R, D and BYS values of the A13 system. Doesn't say to consider more than one of BYS. As seen in ideCAD, it has taken the R=6 value of A13. Since D and BYS have not changed, no change is made for this.