I am renovating an older RV that is made of 4" 3/8 c channel members and has a length of 33'. The original trailer is about 5500# dry weight and I intend to add two 5000# axles and swap out the springs to boost the capacity to 8000# to 9000#. What I am wondering is if the c channel frame can take the extra weight.

I know how to compute simple beam deflection but what I dont know is how to determine the load strength of the C channel beams on the two sides of the frame. I could calculate for a static load at the center of the beam but that would result in massive overkill in design since the load wont be all at one point. So right now I dont know how to calculate it.

So the question is, given a target GVWR on a trailer, how do you calculate the size of the steel members of the frame and how do you calculate the number of cross members other than the two ends are necessary?

Finally does anyone know a good mechanical design book that doesnt require a mechanical engineering degree?

Thanks in advance.