Stepped Column Design

[CASALA]

I am analyzing an existing W10x88 compression member that is has (2) 1/2"x9" plates, each welded to the top and bottom flanges so as to 'close in', or 'box in' the member. Furthermore, while the W10x88 is over 40-ft long, the 1/2" plates are only about 15-ft long and centered about the midpoint of the W10. While it is obvious that the capacity of the W10 is increased, I am unsure of how to a.) analyze the member without omitting the plates and therefore being overly conservative, and b.) how to verify that the welds are adquately sized. After doing some research, I'm let to believe that this is a 'stepped column' problem and have found very little support info on the topic. Does anyone have an idea of how to determine the capacity of a 'stiffened' column like this one and verify that the weld is suficient?

Thanks.

 

[rb1957]

FE is a simple enough solution these days. i've seen several (proprietry) design manuals with solutions for stepped columns. in your case i'd expect neglecting the reinforcing plates is only slightly conservative.

 

[civilperson]

Ignore the plates for strong axis bending strength, small gain by optional use of added capability in weak axis flexure.