Steel column repair

[tebodm]

We have designed a repair for deteriorated steel columns, similar to the one shown in the attached photo. Typical repair is to shore the structure, remove concrete around base of column, cut off deteriorated section of column, weld baseplate to bottom, embed reinforcing steel into existing concrete and cast a concrete pedestal to extend up to the new baseplate elevation. We would shim and grout underside of baseplate and then remove shoring.

Of course the contractor always wants to do it differently. He would like to complete the repair essentially as designed, but he doesn't want to shore and cut the column out. Instead he would like to install a split baseplate around the column above the deteriorated steel and drill in treaded rods into existing concrete and then "jack" the underside of the baseplate using nuts on the rods to "unload" the column before casting the new concrete pedestal. My questinon is would he be able to actual "unload" the column and effectively pretension the bolts so that the load would be transferred to the new concrete base? The dead load on the column is only about 20 kips. I know the baseplate would need to be thick enough to resist bending, and rods sized for jacking forces.

 

[madmantrapper]

I like your method and have done it many times. I do think his method will work but yours is a much cleaner job and less risky.

 

[TheMoonlitKnight]

For this situation, we usually specify welding bars or studs to the existing column, clean the corroded steel, apply an inhibitor, and cast the existing column in concrete to create a composite column. No jacking and minimal steel work. Mainly for gravity columns I would say...

 

[tebodm]

Thanks for the responses. This is just a gravity column and it will only have dead load applied during the repair. I like the idea of welding studs onto the column.