Steel column axial strength

[Robbiee]

Hello,
I went to check a steel column in a parking garage that had some corrosion at the bottom. The column supports 6 stories above and is subject to only axial loads, no lateral braces and no moment connections. After cleaning the corrosion there was some loss in the sectional area. The column is corroded only at the bottom, from the top of the slab to the base, which is about 12". Now, How to assess whether the column needs to be reinforced or not? I am thinking of calculating the member axial strength and compare to the current sectional axial strength with the loss of area. if the sectional strength is equal or greater than the member strength then I won't reinforce. If not, then go through the calculations of loads on the column and see if the current section is acceptable.
Any input is appreciated.

 

[dik]

Can you extend a short 'pier' up a foot with concrete after coating the column with a zinc rich primer. If the corrosion isn't too bad, the area of steel for resistance would be close to phi*As*fy since you are not looking at buckling.

Dik

 

[MotorCity]

Your approach sounds reasonable. Unless you have significant section loss, you probably wont need to reinforce. At the very least, you should provide some form of protection to prevent future corrosion as dik suggests.

 

[Robbiee]

Thanks dik and MotorCity. Yes, some form of corrosion protection will be done. I am not sure if an encasement with a pier as dik suggested will be acceptable to the owner, but will propose it.