Structural Steel Column with Class 4 Section - CSA

[ask111]

I have a steel column - a Canadian W section : In compression, the web is Class 4, and the flange Class 1. In flexural compression, the flange and the web are both Class 1. The column is subjected to both pure compression as well as flexural compression. I am told that by my superiors, it is not safe to have such a section.

 

[ajh1]

As long as the appropriate clauses of S16 are evaluated, there is no particular reason why that sort of a cross-section is any less safe than any other. There are effective width reductions that would apply to the web in compression, but they should have only a minor impact on the overall strength of the section. If such a section was unsafe, the code would not permit it.

 

[JoshPlumSE]

There are some easy ways to deal with this sort of section:

1) De-rate the material. Meaning you use a reduced yield strength until it is no longer classifies as a class 4 section. If the member is satisfactory for stress or strength with the lower yield material, then the member is satisfactory. I believe there is a section in the CSA code which specifically allows this. Though I don't have the code in front of me off hand.

2) That same section in code has an alternative (similar to the cold formed codes) where you remove material from the web until it would no longer be classified as a class 4 section. Then you re-calculate all your section properties with these reduced dimensions. If the member is satisfactory for stress or strength with these reduced properties then it is satisfactory. I believe this is also specifically allowed by that section in the CSA code. But, I'm just going off of memory.