Frame welding question

How about the steel web between the two flanges. Mine is rusted through in places. I would like to have the rusted parts removed and steel plates welded in. Has anyone had this problem and had it fixed? How long will the repair last? Some of the rusted out areas are at where the struts come down and attach to the webbing, there are support beams running side to side between the frame rails.

This is a 2002 Transcraft D-Eagle stepdeck. There is no contact information on Transcraft's website to contact the manufacture.

 

Pictures would help a lot. That being said on dump trailers they have upright channels that go between the upper and lower flanges. These have a tendency to rust out and are replaced fairly often without troubles. I've seen guys fit a new plate on top of the old web of a flatbed and weld it to the upper flange and the lower flange and at each end. I would make the plate as long as practicle. The problem I see is that the frame crossmembers on the inside of the frame are only connected to the old web which is already cracked /rusty without direct connection to the new plate. It also changes how the frame flexes so it would be smart to do it to both rails. I wouldn't be afraid to do it to an old paid for trailer but you are probably just buying time before having to get a new trailer. Good luck