<p>An earthquake's effective duration is an important parameter that can indicate the damage effects on structures, which are not regarded in current seismic design methods. This issue can be exacerbated in concrete moment frames that have shown significant vulnerability in past earthquakes. Therefore, controlling these effects and providing a method to increase the safety margin for this case can be very important. Using a steel S-shaped steel plate damper (SSPD) that has shown adequate deformation capacity and high fatigue resistance can be recognized as a suitable option in this field. For this reason, the present study investigates the effects of long-duration earthquakes (LDEs) on the seismic response of intermediate concrete moment frames, both with and without S-shaped yielding dampers. To follow this trend, three concrete moment frames with varying numbers of stories were designed, and S-shaped dampers with suitable dimensions were designed for them based on the seismic demands of the frames. In the next step, the models of the relevant dampers were analyzed by cyclic loading as nonlinear finite elements, and their nonlinear behavior characteristics, including deformation, stiffness, yield strength, and ultimate strength, were discussed. In the next step, their connection to the designated frames was carried out based on the behavior determined for the damper. Then, the response of the frames without and equipped with dampers, including base shear, maximum displacement, drift, and energy dissipated in the frames, was examined. The results obtained from the finite elements show that the thickness, width, and diameter of the damper are the most important geometric characteristics affecting its hysteresis behavior, respectively. Also, the results of nonlinear time history analyses of frames in LDEs showed that the drift in the frames is reduced by 48 percent. Finally, the SSPDs dissipate about 70 percent of the energy caused by LDEs, indicating their effectiveness as energy-absorbing devices.</p>