Need to figure out ramps and ramp angle for step deck semi trailer

I just bought this step deck semi trailer. I do own a hydraulic beavertail trailer also, but I wanted to set this stepdeck with some kind of a folding ramp as well. The most frequently driven equipment for me is forklifts up to 40,000 lbs total weight. What sort of option do I realistically have and what ramp length (and angle) is most advantageous. SOmething that would work in wet weather safely without use of winches? Thanks