John_G:
One of the best developments and presentations on this topic that I’ve seen is the European Yield Model (EYM). I’ve seen it as relates to bolted, et.al. (doweled) timber (wood framing) joints in various Wood Engineering text books, and the National Design Specification (NDS), AF&PA, American Wood Council, for wood framing design. Certainly, some of the material properties and behavior would have to be changed, but the general theory on the problem should still apply even if you are using plastic instead of wood. A number of good Strength of Materials and Theory of Elasticity texts would be helpful in understanding the various subjects which are part of this development. In particular, take a look at Hertz bearing and contact stresses.