To study the effect of three limit states (force limit state

displacement limit state

and compound limit state) of a liquid viscous damper on the seismic response of single-degree-of-freedom (SDOF) systems

the three limit states of the viscous damper were simulated

and a reliable numerical analysis model was obtained by Ruaumoko-2D. Then

the reinforced concrete structures of two and ten storeys were modelled into two equivalent SDOF systems

each of which was connected in parallel with a viscous damper. Time history analyses under the increasing action of multiple seismic waves and sine waves were conducted respectively to investigate the influence of the force limit state

displacement limit state

and compound limit state of the viscous damper on the SDOF system response. By comparing with the SDOF systems without considering limit states

the variation of the displacement ratio with the peak speed of the ground motion was obtained.