During an earthquake, a considerable amount of kinetic energy from the ground acts as a lateral force on the structure, and this energy causes damage to the main components of the structure, including beams, columns and joints. To reduce the effects of earthquakes on the structure, one of the best methods is dissipation of the energy applied. For this purpose, there are various methods, one of the most practical of which is dampers. Dampers are attachments to a structure that dissipate energy and reduce damage to structural components. The present study examined the TADAS yield damper (Triangular Added Damping and Stiffness) and reliability of the structure equipped with this type of damper (particularly the reliability index) considering the uncertainty in ground motion (ground acceleration) and duration of earthquake. To achieve the objectives of the study, reliability index of the structure was calculated and compared in two modes, steel frame with damper and steel frame without damper, based on criterion of failure and drift and base shear. The results show that dampers dissipate energy from the earthquake and improve reliability and, consequently, reduce failure risk.