Pressure treated lumber is specified for many exterior applications because of its resistance to insect damage and fungal rot. But how does it compare to untreated wood, mechanically?
For example, consider a rim joist supporting the ground floor of a residential structure with a pier and post foundation. If the joist has been damaged by rot in a location that is impractical to fully protect from exposure, I might be tempted to replace the joist with a pressure treated member of the same nominal dimension (in addition to proper flashing) for added protection in that location.
Since this is an existing structure, by far the easiest approach is to use a member with the same dimension to replace the rotted joist. However, this relies on the new member meeting the same load-bearing requirements as the old member.
Building codes should provide enough wiggle room that in this particular example, there's not much of a safety concern for the homeowner. After all, the rotted joist had not failed, and it would definitely have less strength than the member was originally rated for. In practice, treated and untreated members may be manufactured from different wood species with different mechanical properties to begin with; for the purposes of this question, assume the species is constant.
Does pressure treatment result in a member with more or less strength in tension, compression or torsion? Does it affect the durability of the wood* in ways not related to rot or insect damage?
* Not the fasteners; that's a different issue that's pretty well-covered online. See this page from Simpson, for example.