In the current AISI specification, there are two different methods for calculating the effective widths of longitudinally stiffened elements. The first method “B4.1” applies solely to the element with only one intermediate stiffener, whereas the second method “B5.1” works only for those elements with more than one intermediate stiffener. Both methods are accurate in finding the design moments if used appropriately. Although two methods are developed to handle different cases, for some sections with one intermediate stiffener, the second method also works accurately, giving the same result as the first method does for calculating design moments. For some other sections with one intermediate stiffener, the multiple stiffener method when applied to the case of a single stiffened becomes different. These different sections can be distinguished with sets of parameters discussed herein. By comparing the design moments obtained with the same sets of parameters, one can predict when the two methods would have the largest difference and no difference in calculating the design moments and effective widths
