Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Repair of steel W shape column with corrosion near base

Repair of steel W shape column with corrosion near base

Repair of steel W shape column with corrosion near base

I got thrown into the fray of an RFI fire drill where the contractor working on a renovation project found an existing steel column displaying corrosion near the base. The bottom of the column is still encased in concrete/topping and not exposed. It appears that the corrosion occurs up to around a foot from the top of concrete and it is unclear how far it occurs below the concrete (I am not even sure how far down the base is below this concrete) and if there is also corrosion at the column anchorage. The Contractor sent some photos but its difficult to tell the degree of damage and impossible to tell if there is significant section loss from review of the photos. I asked a few questions along those lines to try to get him to investigate and get more information but before he could answer one of my company owners (who is an architect) chimed in with a detail showing two angles welded to the web of the column and epoxy bolted to the concrete topping. I can't put my finger on it, but this doesn't seem adequate to me. Assuming the angles (or likely a bent plate since standard angles aren't made that large) could pass the damaged area and be welded to the web, would they then act to transfer all (most) of the column's axial load in bearing to the concrete topping slab? Even if that were the case I still have too many variables in my head. Will that crush the topping (I don't even know what it is)? Will the angles behave properly with that sort of loading condition (I really don't know how to analyze that condition)? What if the web is so damaged that the flanges are now struggling to support all of the load and the repair to the web only doesn't alleviate the new load path created by the damage? I want to say that I don't feel this is adequate but I want to tread carefully around tossing out my company Owner's recommendation as poor, and especially if it is an adequate solution to the problem and I am over-reacting.

I have seen some folks on here talking about steel corrosion repair and there seems to be a good amount of knowledge and experience on the subject so I'd like to get some of that here as this is my first brush with the issue.

RE: Repair of steel W shape column with corrosion near base

The repair is going to be dictated by what is damaged. Is it just the web? Just the flanges? Both? You're post only indicates damage, but doesn't specify what is damaged. Is the column part of a moment frame, or strictly a gravity column? What kind of load are we talking about?

The angle idea could be feasible depending on what kind of column this is.

Go Bucks!

RE: Repair of steel W shape column with corrosion near base

A picture is worth a thousand words

RE: Repair of steel W shape column with corrosion near base

It sounds like you need to expose the column base for assessment. A site visit is required. The structural engineer should be designing any repair, not an architect.

RE: Repair of steel W shape column with corrosion near base

I worked on a project that sounds very similar to your's. In my case, there was a small room inside of a building on the ground floor. The contractor temporarily removed one of the walls so that they could replace a piece of equipment, and they discovered two columns with heavy corrosion at their bases.

The webs were entirely rusted through on each column - from the inside-of-flange to inside-of-flange, there was no web. You could literally see from one side to the other. The flanges were rusty, but intact.

In the end, I issued a field instruction that went like this:

1. Temporarily support all the steel above with shoring posts.
I gave them a sketch showing the placement of the posts, and I designed the posts including the base plates. In my case, I spec'd HSS 6x6x5/16 tubes.

2. Chip out the foundation pedestals down to the base plates.

3. Remove the bottom portions of each column, including the base plates and anchors, to a height of 4' above the floor.

4. Fabricate and install identical columns/base plates to the ones that will have been removed.
I gave them a sketch showing a splice detail. Check out the attached doc.

5. Replace concrete.
I gave them some concrete specs.

6. Remove shoring posts.

Looking back on it, I kind of wish I would have used a stub column w/ a bearing plate. Potato, potato I guess.

RE: Repair of steel W shape column with corrosion near base

Make sure you do an assessment of the loads against the potential loss of section. Even though its corroded, if the capacity is adequate still, then all that might be required is removal of the corrosion and reapplying some appropriate corrosion protection. Something like NOXYDE is pretty good at encapsulating and halting the corrosion with minimal effort to clean the section. You should remove the concrete to deal with any deterioration that extends into the concrete.

Usually this interface between embedded steel and concrete requires special attention and additional corrosion protection coatings both into and above the interface are required for good long term performance. This usually comprises a band of non-conductive paint (Inorganic Zinc Silicate is used in these parts). This is even true of galvanised steel, it also requires similar protection in this region. It's surprising how often you might see a contractor consider just embedding the steel with the normal primer and painting the top coats up to the interface (path of least work)!

RE: Repair of steel W shape column with corrosion near base

conradlovejoy (Structural)(OP)
Could you please attach couple of pictures of the problem?

Thank you

RE: Repair of steel W shape column with corrosion near base

Often, the worst corrosion is of the nuts on the anchor bolts. So you have to get to them as part of your inspection.

Agent666, it is surprising to see that you use inorganic zinc in repairs of this type. Inorganic zinc requires impeccable surface preparation, and is normally used only in new work. Organic primers, including thick build mastic primers, are the typical choices in repair work.

RE: Repair of steel W shape column with corrosion near base

Yes I was referencing the requirements for careful consideration of this area in new work to avoid the potential of similar issues.

For existing, like I noted, I'd consider something like noxyde as the steel just usually needs a good waterblast and loose bits removed to encapsulate what's remaining.

RE: Repair of steel W shape column with corrosion near base

Fair enough. I'm not familiar with that product.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


White Paper - A Guide to 3D Printing Materials
When it comes to using an FDM 3D printer effectively and efficiently, choosing the right material at the right time is essential. This 3D Printing Materials Guide will help give you and your team a basic understanding of some FDM 3D printing polymers and composites, their strengths and weaknesses, and when to use them. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close