Dear Mihimal,
In general, you do not need to use separate cohesion and friction angle values between static and cyclic loading. This is because your strength parameters, which define your failure envelope, are characteristic of the material under the tested/ sampled conditions. What occurs during cycling loading is a progressive reduction of the mean effective stress related to factors such as development of excess pore pressures.
Regarding the modelling of different constitutive models involving cyclic loading, we recommend you check our materials and reference manual: https://communities.bentley.com/products/geotech-analysis/w/plaxis-soilvision-wiki/46137/manuals---plaxis
Consider that some of our models available consider cyclic loading allowing you to elastic and plastic strains, accumulation of strains or pore pressure and liquefaction.
You can also check our User-Defined Soil Models list: communities.bentley.com/.../user-defined-soil-models---plaxis
Thanks a lot, Stefanos. Can we obtain the code of the soil models defined by PLAXIS (including user-defined soil models) to alter them and use them in our simulation? Since PLAXIS is not open-source software, are they allowing their model code to a third party to alter and use? (When it comes to research work)
As my colleague explained in another post you made, https://communities.bentley.com/products/geotech-analysis/f/plaxis-soilvision-forum/229525/soft-soil-model-plaxis-code, we do not provide any code for our native constitutive models in PLAXIS.
You are free, however, as a researcher to develop User-Defined Soil Models (UDSM) in the same way many have been implemented already.
https://communities.bentley.com/products/geotech-analysis/w/plaxis-soilvision-wiki/45468/creating-user-defined-soil-models
https://communities.bentley.com/products/geotech-analysis/w/plaxis-soilvision-wiki/45391/user-defined-soil-models---plaxis
Note that nowadays all the UDSM files are delivered with the CONNECT Edition application.
Thanks a lot, Stefanos.