In this study,a novel rotational damper called a Rotational Friction Viscoelastic Damper(RFVD) is introduced.Some viscoelastic pads are added to the Rotational Friction Damper(RFD) in addition to the friction discs used in this conventional device.Consequently,the amount of energy dissipated by the damper increases in low excitation frequencies.In fact,the input energy to the structure is simultaneously dissipated in the form of friction and heat by frictional discs and viscoelastic pads.In order to compare the performance of this novel damper with the earlier types,a set of experiments were carried out.According to the test results,the RFVD showed a better performance in dissipating input energy to the structure when compared to the RFD.The seismic behavior of steel frames equipped with these dampers was also numerically evaluated based on a nonlinear time history analysis.The numerical results verifi ed the performance of the dampers in increasing the energy dissipation and decreasing the energy input to the structural elements.In order to achieve the maximum dissipated energy,the dampers need to be installed in certain places called critical points in the structure.An appropriate approach is presented to properly fi nd these points.Finally,the performance of the RFVDs installed at these critical points was investigated in comparison to some other confi gurations and the validity of the suggested method in increasing the energy dissipation was confi rmed. In this study, a novel rotational damper called a Rotational Friction Viscoelastic Damper (RFVD) is introduced. Some viscoelastic pads are added to the Rotational Friction Damper (RFD) in addition to the friction discs used in this conventional device. Reconditioned, the amount of energy dissipated by the damper increases in low excitation frequency.In fact, the input energy to the structure is simultaneously dissipated in the form of friction and heat by frictional discs and viscoelastic pads. In order to compare the performance of this novel damper with the earlier types, a set of experiments were carried out. The evidence is to to test the results, the RFVD showed a better performance in dissipating input energy to the structure when compared to the RFD. The seismic behavior of steel frames equipped with these dampers was also numerically evaluated based on a nonlinear time history analysis. Numerical results verifi ed the performance of the dampers in increasing the energy dissipation and decreasin g the energy input to the structural elements. In order to achieve the maximum dissipated energy, the dampers need to be installed in certain places called critical points in the structure. Ann appropriate approach is presented to properly fi nd these points. Finally, the performance of the RFVDs installed at these critical points was investigated in comparison to some other confi gurations and the validity of the suggested method in increasing the energy dissipation was confi rmed.