Column Reinforcing

[treopolis]

We are working at a condominium along a beach. Reinforcing a pool deck that has seen far too much corrosion from the elements. The pool deck intersects with the main building at a balcony. We have to replace the balcony spandrel beam, but want to avoid replacing the balcony columns as they support other spandrels, and an interior girder for 4 stories and a roof. Our first thought was to just grind back to bare metal and cover plate, even if it needed to be on all four sides. However, we got started grinding back to bare metal and found that the flanges are fairly thinned out and the web is corroded completely through in some locations.

The question is - should we cut our loses and replace the column? Does someone have any other ideas for reinforcing that would develope into what is left of the exist column.

See the attached picture.

Thanks,
Andy

 

[Lion06]

replace it.

 

[swearingen]

At least replace the corroded part...


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[civilperson]

I estimate more than 50% loss of structural strength from photo, replace it.

 

[JedClampett]

Replace it. Don't forget to coat it with something that resistant to salt spray.

 

[kslee1000]

Replace the column would be the best long term solution. However, if the corrosion is limited to the lower part of the column, you may be able to jack up the adjacent beams, cut the baddly deteriorate lower part and attache a same size, or little larger, segment using full-pen weld.

 

[jike]

An idea that may or may not fit with the appearance of the building and lateral system would be to shore up the building cut the column off and replace with a new concrete column. You will have to evaluate whether it is feasible to pursue this option but it may provide the Owner more building longevity rather than replacing the corroded steel column with another steel column.

 

[vandede427]

Steel framed condo on the beach? Who made that design choice?

Concrete, concrete, concrete.

 

[beton1]

I agree with replacement. Only concern would be existing anchorage, you may have to chip down and address this as well. If using steel again (partial or full height), I would at least encase the bottom (4 feet?) in concrete.

 

[asixth]

How did it corrode so much. I always thought the high pH of concrete provided some corrosion protection for any steel reinforcement.

 

[hokie66]

asixth,

Steel column. No concrete. Look at his picture.

 

[apsix]

asixth

"I always thought the high pH of concrete provided some corrosion protection for any steel reinforcement. "

Yes, provided there is adequate concrete cover and quality to prevent the chloride ions reaching the steel over the design life.

 

[blackmaddog]

The best option from the design side is replacement (steel or concrete) however sometimes the expense and difficulty pushes you to find other options. Here are a couple ideas to consider:

1. Box in the I section with plates to effectively replace the web and restore the original section. This requires that there is enough flange steel remaining for welding.

2. Clean the column and encase it in reinforced concrete. This also provides opportunity to epoxy dowel rebar to replace deteriorated anchors.

In response to the corrosion discussion, either steel or concrete should have protective coatings applied in corrosive environments for maximum service life.

 

[treopolis]

Thanks for some of the innovative ideas. I kind of arrived at the encasing the column in concrete idea myself, and liked it for its simplicity, but due to schedule we had to go with a steel solution (steel fabricator already on site). We just cut the column and welded a new section and cap plate back on. It was not a preferable solution, but we put our faith in the fabricator, who seems to have his stuff together. We are coating all the new steel with the Simtar epoxy system. It is used on underwater marine applications.

Andy