The moment resisting frame is a system in which stability and lateral resistance are provided by connecting the beam to the column. The functional mechanism of moment resisting frames to dissipate earthquake energy is through the formation of plastic hinges in beams and columns. One of the most important criteria for the acceptance of sections in steel structures is the criteria related to local buckling, which is one of the design challenges in moment systems. One of the useful solutions to strengthen these systems is the use of concrete-filled tubes, which by intelligently combining concrete and steel results in a more effective system than using them separately.
Usually, in the process of analysis and design, structures are analyzed and designed only as frames consisting of beams, columns, and braces, and the interaction effects of infilled panels are ignored and considered as non-structural elements. Note that the presence of infilled panels can be effective in the accurate evaluation of the seismic behavior of the structure. Therefore, in this research, the seismic behavior of 72 two-dimensional steel moment resisting frame models with CFT column and 3D sandwich infilled panel has been investigated with two approaches, in the presence of the infilled panel and without the presence of the infilled panel, in the SAP2000 software environment, using pushover analysis. In these investigations, the effect of factors such as the ratio of steel yield stress to concrete compressive strength in CFT columns for concrete compressive strength of 21, 25, 35, 48 and the steel yield stress of 240 MPa, as well as the ratio of span length to floor height (L/H) 1, 1.5 and 2 and the number of floors is 5, 10 and 15 floors. In the process of non-linear solution, fiber hinges have been used in beam and column elements, and non-linear layered shell elements have been used in infilled panels. The results show that the existence of the sandwich infilled panel reduces the lateral displa