Corroded Steel Columns 1

[sigma1]

We have a case where the bottom 6" to 8" of the steel columns, supporting a residential appartment complex, have lost about 25-30% of their properties to corrosion and have to be retrofited. The columns are encased with concrete for what appears to be fire protecion and the bottom 6 to 8" portions are embeded into the concrete slab. The building is about 40 to 45 years old and there are no drawings available. In addition, the steel members do not appear to be close to any members listed in AISC.

Questions:
1. Where can we find properties for these members if any
2. Are there any pitfalls in dealing with this type of structure?

Any recommendations will be appreciated

 

[dik]

Is there enough material left to consider the column as a reduced section for the deteriorated portion? If there is, then it's a matter of providing a coating repair that will prevent further deterioration.

Can the lower portion be encased in new concrete to provide sufficient strength? It may be necessary to weld studs/lugs/straps/etc. to it to develop the new concrete.

It is possible to weld straps to the faces of the columns to build up the material as required.

Dik

 

[sigma1]

We did not performed any checks yet but I do not believe it would be enough without strengthening.

Thank you for your information.

 

[dik]

If only the lower portion (few inches) is corroded, then it may be OK to use .6*Fy*As or something of that ilk. Not likely is there is a moment at the base...

Dik

 

[JAE]

Find old structural shape data via this excellent resource from AISC (Design Guide 15)

AISC Design Guide 15 Link