Repairing and rehabilitation of existing steel columns

[Ali95]

Hi everyone,

I have an existing braced steel frame structure that is supporting a grain silos. The structure is 60 years old and it is in good condition except for a few columns, which are heavily corroded at the bottom (see attachment), some of which have lost almost the whole web at the bottom (were the columns are connected with the ground slab), I am looking for a remedial solution to keep the structure for few years until the new structure is built, can someone with relevant experience advise on a viable solution to repair these columns, and how to ensure that if a column fail the structure will not go through progressive collapse?

My initial suggestion:

1- Strengthen the with two welded plates.
2- encase these locations have concrete and shear studs.
3- connect the columns using ground tie beams, so no disproportionate collapse happens.

 

[mtu1972]

I had a similar situation with columns in the basement of a paper manufacturing plant about 25 years ago. These columns were on concrete piers that extended a foot or so above the floor slab. I did a combination of what you have described.

I reinforced with plates where the corrosion was not too bad.

Where the column section was virtually nonexistent, I had new horizontal “base plates” welded to the wide flange column section. I don’t remember exactly, but they may have been two or four plates welded to the webs and flanges of the existing column. Stiffener plates were probably also added to facilitate making the plates work together.

Then I had the slab removed to gain access to the footing and had a larger reinforced pier poured to a height above the original pier. After the pier cured I had grout placed to finalize the support.

I never heard of any problems with those columns, but I left that company and have been retired for many years now.

gjc