Steel column Repair 1

[RanarT]

I'm a fresh graduated civil engineering program and now I work for a petrochemical company. My plant area is located nearby the sea.

My problem is I'm having a rusted steel column at the end section that connects to the foundation and the rusted anchor bolt also as you can see in the picture below. My questions are:
1) what is the steps to decide whether the anchor bolt should be replaced or not?
2) what is the steps to assess whether the column should be replaced totally or partially
3) if the column or the anchor bolt should be replaced/repaired then what is the most efficient method?

Thanks guys

 

[BAretired]

It doesn't look too bad to me. Are the anchor bolts required to resist any significant force? If not, I would sandblast and inspect again. Remove the nuts; clean and grease them and the bolt threads. Apply epoxy paint to sandblasted surfaces. Tighten the nuts.

If the bolts are carrying significant force, you may want to check them a little more carefully but turn of the nut tightening is a measure of the bolt strength and is likely sufficient for your purposes.

BA

 

[hokie66]

I agree with BA that the column can be saved and that the corrosion of the base is not too bad. You need to remove all that loose stuff and sandblast. I would use an epoxy mastic type coating like Carbomastic 15, which is forgiving of less than ideal preparation.

The nuts are gone, which is typical. They are usually the first thing to go, although I don't know exactly why.

The bolts may still have enough meat left, but the threads to receive new nuts may be a problem.

 

[Ron]

Agree first step is to sandblast, gritblast or dry ice blast this to remove all exfoliated steel. It looks like there might be weld separation along a fusion line for the fillet weld on the right side. Check all welds for cracking after blast cleaning. Even if you have section loss that might be significant (though it looks like that will be isolated), you can add section back by welding additional plates/gussets.

Chase the threads on the bolts with a threading die. If they are still relatively intact, put new nuts on as noted. If the threads cannot be restored, check the anchor bolt material for weldability and consider welding a mild steel block over the bolts in place of replacing the nuts. The block would have a tapered hole that would allow a better and deeper penetrating weld to hold the bolt. A fillet seal weld could then be placed around the bottom of the block to reduce corrosion potential.

 

[bridgebuster]

Ditto to all the above. You have to clean up the steel to see how bad it really is. I've inspected 100's of bridges and sometimes it is as bad as it looks and other time no.

hokie - I agree with you about the nuts. Maybe we can get an FHWA grant and study it for a few years.

 

[XR250]

I agree with others. Wire brush it and there is likely a bunch of steel left over. These tend to look worse than they are as the rust expands.
You may be able to weld the column to the bolts instead of re-thearding them.

 

[RanarT]

The structure holds an overhead crane with the capacity of 10 Tons. The rusted base plate is marked as Base (01/012) in the picture attached. My next question is, Is it possible to make a new thread on that rusted bolt? How do you do that?

Thanks for your help

 

[SlideRuleEra]

RanarT - I agree with the others that the structure can be repaired. I would not apply any torque to the anchor bolts (such as using a die to rethread). They could wring off either at the top of the base plate or at the concrete/anchor bolt interface. Instead, after cleaning, go straight to Ron's suggestion to check for anchor bolt weldability and weld on a cap.

Since an overhead crane could put horizontal forces on the anchor bolts, I would then encase the bottom foot, or so, of the column with a reinforced concrete collar that is anchored to the surrounding concrete.

The fact that the plant is near the sea is why I'm skeptical of the condition of the unseen part of the anchor bolts. The column/anchor bolts looks for all the world like it has been submerged in sea water, or perhaps subjected to corrosive chemicals spilled at the plant.

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