Buried Steel Column Base Plate 1

[structuraldan]

After exhausting all options, I am stuck placing steel column base plates below grade, directly on the footings.

My question is: What is the best method of protection?

I have previous, similar designs to my current project, as well as the more experienced designers in the office, and the best suggestion I am getting is to maintain the status quo, using the standard "Apply 2 coats of black asphaltum to below grade steel." I have made many design improvements over the previous projects, so I am not satisfied with this answer.

I understand this was the standard practice for many years and after doing some research I have not found any new innovations.

Does anyone have any suggestions?

 

[DaveAtkins]

When the slab-on-grade is poured, won't it surround the base plate with concrete protection? I am assuming you are talking about an interior column, with the top of footing 8" - 12" below the top of the slab-on-grade.

DaveAtkins

 

[WillisV]

Agree with Dave - we do this all of the time - typically with the top of baseplate up to 2ft below finished floor they can still just turn the slab on grade down onto the footing around the column and that concrete is more than enough protection.

 

[structuraldan]

Columns support an exterior canopy adjacent to building. A 4 inch slab on grade will be poured around the columns, but the top of slab will be 22 inches above top of footings.

That makes a massive turn down, might require formwork, and needs about 12 cy of extra concrete over the entire project. This leads to using a pedestal with surface mounted base plate instead. I have already eliminated this option.

I'll use the standard coating if I need to, it just seems to be an outdated practice.

Thanks for the quick posts, its appreciated.

 

[JStephen]

Perhaps consider a cathodic protection system- will likely cost more than the 12 cy of concrete, though.

 

[structuraldan]

'JStephen' - Agree

What about a sacrificial zinc anode placed near the base of each column?

 

[minorchord2000]

why is the footing so deep in the first place?

 

[SperlingPE]

Can you get a sonotube form around the column and encase the column in concrete below grade?
No asphalt, probably less concrete than turning down the slab.

Asphaltic coating may be antiquated, but the cost for other solutions make it a good choice.

 

[J1D]

Encasing the column with concrete will make the column base restraint to be “fixed”, in another word, this requires good anchorage between base plate and footing. The best way is to bring base plates up with pedestals if the columns are not constructed, from my view.

 

[WillisV]

12cy concrete x $80/cy = $960 - not that much.

 

[apsix]

If you're really concerned about corrosion you could use Denso tape;

http://www.densona.com/Index.htm

Otherwise the solutions noted above are fine.

 

[Ron]

structuraldan....sometimes the old stuff still works! There is absolutely nothing wrong with an asphaltic mastic or coal tar mastic coating for steel protection below grade. It's a simple solution and doesn't require maintenance...just make sure they do it right.

Change is not necessarily improvement nor innovation. Matching the cost-effective solution to a problem is still innovation, since so many times that doesn't happen!