Need a better understanding about how spring hangers are treated in dynamic analysis. CII documents suggest program designed springs stiffnesses are carried into dynamic solution but when I check "Active BC", I see a totally different stifness and sometime ZERO stifness value. Could anyone help what I am missing here

CAESAR II includes spring support stiffness into the dynamic model - both user-defined and program-sized spring rates.
Zeroes will be shown for nonlinear restraints that are inactive for the load case used to set the "nonlinear restraint status" on the dynamic input control parameters.
"Different" stiffnesses will appear if friction is accommodated in your dynamic analysis.

Many thanks for the reply.
When both user defined and program sized Stiffnesses are taken into account, then what is the reason "Active BC" shows stiffness as Zero.

Does Caesar only account for stiffness of the springs and NOT the load it carry in static analysis?

Could you help me understand how springs Non linearity is treated into dynamic analysis.

Any thoughts ??

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.