Cbush is a 1D element. It is used to model stiffness/damping in between 2 nodes which can be coincident or non-coincident. Refer PBUSH in qrg for all options avaiable in it.
CBUSH/PBUSH can be used to defined stiffness in X,Y,Z,RX,RY,RZ.
It can be used in Sol 106 with CBUSH/PBUSH/PBUSHT if you want to define a Force Vs deflection that needs to be followed. In frequency response it can be used to vary the Stiffness with respect to Frequency.
