[GeoMechanicsApplication] Truss backbone law

[WPK4FEM]

📝 Description Addition of a backbone with elastic un- + reloading constitutive model for truss elements.

🆕 Changelog

• First setup of model
• Necessary fix of strain measure for linear truss element.

[avdg81]

Hi @avdg81 and @WPK4FEM , nice work. I have just a few minor comments in addition to other comments. @avdg81 , I've found std::adjacent_find, is it possible to use it with ublas Vector? If yes, it can be used for ascending check. Thank you.

Hi @markelov208, many thanks for the thorough review. Much appreciated. In most cases, I have adopted your suggestions.

Regarding std::adjacent_find: I think that algorithm serves a different purpose. My understanding is that it finds the first pair of the consecutive elements that compare equal. I don't see how I could use that here. In that sense, std::is_sorted comes closer to what I need. However, in that case, the error message cannot be made as descriptive as it is now (where we mention the values not being ascending, and at which positions in the list they can be found). So I have left it as-is.