straighten trailer frame

Still working on reconditioning an equipment trailer- 1980's model
eager beaver 12k rated. It has 6" I beam frame rails. I have the
floor boards removed and have cleaned and primed the frame. Now that
I have it on a flat concrete slab, I can see that there is a 1" high
upward curve in one rail over the front axle. It has a one piece
frame rail all the way from the tongue to the beaver tail,which curves
down about 4' from the rear. The curved I-beam at the back is factory
butt welded to the flat I beam section. To get the hump out of the
flat I beam, I am thinking about notching the humped area all the way
down to the bottom web, and then jacking up behind and in front of the
notch until the rail is flat again, then welding the notch closed.
Since the I beams are factory butt welded, I don't see any problem
with this approach. I also have thought about blocking up the frame
and putting down pressure on the bent area with my excavator bucket.
The excavator weighs 40k lbs, and I am sure that I can bend the rail
downward. I am concerned that if the i beam yields too suddenly, I
could create a worse problem than I have now. Any advice as to which
method is best?

A local truck frame shop quoted me $125.00 to straighten mine. But yes, if I could bend mine myself I would(or will).

Welding a beam back together in that spot will require more than just welding, you should plate the upper flange at least to maintain strength. Bending it back with your excavator will be tough just as you suspect and will likely result in it just rebending again. I would use heat to shrink it back straight. Use a rose bud on your torch to heat about 3" of the top flange and a v down to the lower flange to just barely showing red, then cool it with water. You don't want to get too hot so you damage the temper of the beam. You may need to reheat a couple times and in different places to get it right.

Jon, thanks for the idea on heating the beam. My acetylene cylinder is not big enough to run a rosebud tip. I think I will try bending the beam with the excavator, but block up underneath where I push down with the bucket to protect against collapsing or reverse bending the i beam. I am unable to find any truck frame service that will be available any time soon to have it straightened.

Just be careful you don't twist it when you do it with your excavator.

You can do it with a large cutting tip too, just takes longer.

Straightened it out today with the excavator. It is not perfect, but basically got it back in alignment.