In recent decades, one of the basic topics in research related to the design of earthquake-resistant structures has been the Introducing new methods to reduce the response of the structure against dynamic forces by using control systems. Rotational friction damper is one of the new methods to improve the ability to increase damping. The general mechanism of this tool is to significantly increase the damping of the structure through the absorption and consumption of the energy input to the structure. These dampers have high energy dissipation capability and low installation and maintenance costs. In most of the past researches, the seismic behavior of steel structures equipped with rotational friction dampers has been investigated by researchers in a laboratory and on a small scale. However, the effect of rotational friction damper in steel structures with CFT column has been investigated less. Therefore, following the research of other researchers, in the current study, the effects of seismic behavior of steel structures with CFT columns equipped with rotational friction dampers (RFD) have been investigated. In the process of non-linear solution, fiber plastic joints have been used in column, beam and brace elements. While validating the numerical method used and performing various necessary numerical analyses, the obtained results have been evaluated. In this research, the seismic behavior of 30 models of a simple frame structural system with a CFT column equipped with a rotational friction damper was investigated in the Etabs software environment in the form of dynamic analysis of nonlinear time history under the El Centro earthquake with a maximum acceleration of 0.35 of the gravitational acceleration value. In all models with a fixed height of 3.4 meters, the effect of various factors, including the length of 3, 5 and 7 meter spans and the number of 3, 6, 9, 12 and 15 story, with and without dampers, have been considered.
The results show that the damping effect