Use DzlBenz' 5000 lbf per tire, assume a tire is 10 inches wide (WTF, I have no idea how wide the truck tire is, but it doesn't matter as you will see) -
As the tire creeps up the ramp, it will load one web of the beam before the other, so the compression stress in that web is 5000/(10*0.188) = 2.7 ksi.
If that beam is A36 or similar mild steel, and I needed an answer right now and didn't have time to calculate the compression buckling allowable because there are terrorists that needed to be killed right now, I would drive the truck over without a second thought. If the ramps are an inverted U-channel, the stress is siginificantly higher. If the ramps are flat bottom boards, the area served is larger than the tire footprint and the actual stress is lower. Since this is a beam on an elastic foundation, unless there is something unusual in the configuration, that will also reduce the effective stress even further. If I had a manual handy, I would calculate the buckling stress, but I don't, so I ain't. Even with a factor of safety of 5, the stress is just over 13 ksi. Unless these tubes are manufactured from peanut butter, they will easily support 5000 pounds at a tire.
You are more likely to have a stability problem with the tubes rolling over due to a lack of lateral restraint.