Corroded bolts and nuts in steel column base plate 1

[Zishan.A]

Hi, I am working in the manufacturing industry as civil engineer and while inspecting the structure for any integrity issues, i come across very often major steel columns with totally corroded nuts on anchor bolts. It is very hard to replace the columns, as it is expensive and would be major construction work, what suggestion you have if thread profile on bolts can not be restored? anchor bolts are fixed in reinforced concrete at base on ground level.
Usually it is rule of thumb to not use weld on bolts, what options do i have in this scenario?
Thanks in advance.

 

[human909]

There are a heaps of possible solutions. More information is needed. If the existing bolts are in good condition you can likely reused them. But do be careful if the nuts are corroded you need to ask yourself the condition of everything else. If not plate and other anchors. Without pictures and context it is hard to narrow down on solutions.

 

[hokie66]

Zishan,

Your experience is unfortunately typical of industries these days. The inspections you are doing now are not timely. The nuts on base plates are almost always the first thing to go if left unprotected.

Firstly, determine if a die will fit the bolts, even for a slightly reduced nut size. It is always best to reuse the existing bolts if possible, even as part of the connection. As to welding, it depends on the type of steel the bolts are made of. Many anchor bolts are mild steel, and easily weldable.

 

[SlideRuleEra]

...major steel columns with totally corroded nuts on anchor bolts.
...thread profile on bolts can not be restored?
...anchor bolts are fixed in reinforced concrete at base on ground level.
...what options do i have in this scenario?

So the anchor bolts are inaccessible because the existing column/baseplate are in the way and cannot be moved without plant outage and major expense:

Sandblast the corroded steel in place and encase the base plate and end of the column in reinforced concrete with chemical anchors in the floor:

 

[Zishan.A]

Hi SlideruleEra, thanks for your post, did you mean that I should provide new anchor plate with bolts and weld anchor plate with existing column? and encapsulate previous with concrete.

 

[SlideRuleEra]

Zishan.A - If the situation is as bad as you describe, nothing new... just clean (sandblast if practical) and encapsulate.

If an attempt is made to remove/replace anything, there is always the possibility of unintended consequences... you may start a chain of events that leads to shutting down the plant/ replacing the column immediately (unplanned outage).

At a minimum, encapsulation will delay major work until a planned outage.

I never had to encapsulate at any of our electric generating stations, but would have is necessary. We could usually wait.