These types are movement are hard because of gravity, so while a 100KG is still 100KG, when unloading or lifting up stairs, you're fighting against gravity, which give what I call a "perceived weight." This calculator provides an estimate of the perceived weight.
I use the perceived weight for purposes of HSE, and design a route around this value.
On stairs/ramps, part of gravity pulls the load downhill. Your team must support weight and resist that pull.
A simple model is perceived mass ≈ m(1 + sinθ) — where m is the object’s mass and θ is the stair angle.
Contact me (Lee) on 077 888 211 21 or email lee@venture-logistics.co.uk