How is stiffness matrix for Pfast calculated in Patran or outside Patran?

[VH88]

So Pfast card requires stiffness matrix KTi and KRi to represent the stiffness of the joint with respect to fastener's and joining plates' topology. Patran gives user a freedom to fill out KTi and KRi. Patran also lets user select one of the Patran's in-house fastener stiffness formulas such as "Douglas", "Huth Hi-Lok in CFRP", "Huth solid rivet", etc; Kti will be automatically calculated if user selects the formula option (user still has to fill out KRi though).

I know each company has its own practice to model fasteners. Please comment below your experience with stiffness matrix for Pfast or any other approach (Pbush, Pbar,etc)

 

[VH88]

MSC just replied to me that the KT1, KT2 and KT3 formulas can be found in the "Patran Interface to MSC Nastran Preference Guide". I am still interested in knowing how KRi should be calculated. Thanks