Fb to use when strengthening an existing Wf with a tee

[samdamon]

I am strengthening a variety of wide flange shapes made from A7 steel (Fy=33 ksi) by welding tees on the bottom. When checking the combined superimposed stresses on the top flange of the strengthened section using ASD methods, is there any justification for using a higher allowable Fb than .66Fy? Don't see it in the literature but was wondering what others do in this situation.

 

[kslee1000]

EIT:

You are correct. The transformed section is best for materials with different elastic modulus. I have mis-read your post, please ignore my previous posts.