We need to keep in mind that there are various limits to address .. including ..
(a) shear strength ... related to vertical tearing failures .. a bit like supporting a sheet of ply on two beams 5-6 inches apart .. and then driving a motor car wheel along the central bit of the ply
(b) bending strength .. related to failures like might occur by excessively loading the centre of a longish plank supported at each end on two ladders. Also, with longer aircraft, particularly, we are concerned with fuselage bending .. so there will often be limits which permit lots of load over the wing carrythrough section ... progressively reducing as the distance from the wing increases. Often a critical consideration with composite floors due to the sudden onset failure which can occur with composites.
(c) local bearing strength (crushing) considerations .. related to failures similar to what happens when you belt a surface with a hammer or put some sort of high load item with a small support footprint onto the surface.
From a practical point of view, the W&B (sometimes the AFM/POH) manual will detail the limitations and then it is up to the load control/freight people to get the sums right to avoid problems.
.. and, if a pilot/operator cheats ... the effect on calculated and specified fatigue lives can be compromised significantly ...
The general message with all limits is that they are there to protect the innocent ... one ventures outside the limits in ignorance of the specifics which went into their calculation.