In my mind this is what happens- Chucking
Good case scenario.
Your scenario is what we call freeway hop....just another of the many causes for chucking.
Freeway hop is hard to get a handle on why the combo does it and why other truck/trailer combos have no hop issues at all on the same concrete freeways with those type expansion joints.
My state tried angled joints on a couple of major US highways but slabs still tilted.
There a bitzch till the state chips the slabs flat to each other.