Boundary conditions modeled as "hangers" in CAESAR II have stiffness and preload components which are both part of static analysis (the preload is itemized as "H" in static load case definition). These hangers are, by definition, linear and their stiffness is included in the dynamic analysis but their preloads are not. (When CAESAR II selects a hanger, in addition to the preloaded spring, the program may instead choose a rigid vertical support or a vertical constant force. These, too, are linear.) "Restraints", on the other hand, have stiffness with no associated preload and these restraints may be nonlinear. Restraints, if nonlinear, may be either active or inactive in dynamic analysis. The user defines which static load case is used to set the active/inactive status of nonlinear restraints. The Active Boundary Condition report in dynamics output shows the stiffness values used in the dynamic analysis.
If your Active Boundary Condition report does not show hanger stiffness, whether selected by CAESAR II or defined by you, I have to think that something else is going on here and I should stop guessing. If this is the case, I suggest you open a support request through Smart Support so we can review your specific case.