The "Damper" type link element in SAP2000 has two distinct set of properties. The linear properties of "Effective Stiffness" and "Effective Damping" are used in linear analysis cases and assumed to be in parallel. The nonlinear properties of "Stiffness", "Damping Coefficient" and "Damping Exponent" are used for nonlinear analysis cases and assumed to be in series. If the user does not need to use a "Damping Exponent" other than 1 they can use the "Linear" type link element. This allows the use of a linear dashpot with a linear stiffness in parallel for both linear and nonlinear analysis cases.
Link