The web of a H-section column has been completely corroded at the air-moisture interface with the concrete encasement leaving a hole in the web. The proposal is to break out the existing concrete and weld plates onto the web that will bridge over the hole in the web and will be welded on all four sides to good steel.
The plates will be on both sides of the web. If the web is 8 mm what should the thickness of the plates be? At a minimum should they be 4 mm to reinstate the loss of section?
You need to shore the structure first. Welding heat will lower the strength of the steel.
then you should use needle gun and grinder to bring the corroded material to bright metal.
The patch plates should be thicker than 1/2 of the web thickness. H.S bolts are preferred method of fastening, but if welding is used it should be intermittent and done in alternate runs to avoid heat strains.
The job must be primed and sealed before newly removed concrete is replaced with high strength repair concrete with proper acrylic admixture for strength and curing.
