I'm designing a structure where I don't have large loads. I want to use W8 columns but I don't even need the lightest section shown in the AISC manual (a W8x31). I'd like to use a W8x18 to save on steel costs. I know I can calculate the capacity by hand using the spec which I did and it's fine. I also put it into a 3D model. It's a large platform with bracing and lateral loading. My question is regarding the use of sections lighter than those shown in the AISC compression tables. Is it recommended to use the lightest section in the table or can one just calculate the required section? What are the considerations?