In recent years, sandwich panels have become one of the common infill panels in the moment resisting frame systems. The behavior of these panels has always been discussed by researchers.
In the present study, the behavior factor of moment resisting frames with the sandwich infill panel has been investigated. Also, an equation has been established to calculate the behavior factor, based on various effective parameters. In this regard modeling and nonlinear analysis of moment resisting frames models with the sandwich panels were performed. In this modeling, some effective parameters in the performance of moment resisting frames with the sandwich infill panel have been considered in various and variable ways. These parameters include: the number of stories (2, 4, 6, 8, 10, 12, and 15), the ratio of span length to story height (1, 1.5, and 2), the design base acceleration (0.35 and 0.3), the ratio of concrete compressive strength to the longitudinal reinforcements yield stress (0.08 and 0.075), the effect of the gap between the frame and sandwich panel (0 and 20 mm), the flexural frame system with different ductility (special and intermediate). After calculating the behavior factor using valid methods, a database was created by using the behavior factors obtained from the models. A mathematical equation was conducted by GeneXproTools software to obtain the behavior factor. The main purpose of this research is to establish an equation to obtain the behavior factor of the moment resisting frames system with the sandwich infill panel based on effective parameters. After extracting the relevant functional equations, the sensitivity and parametric study of the behavior factor concerning the parameters of the mentioned variable have been studied. After sensitizing the input parameters to improve the performance of the final equations, the behavior coefficient estimation equations for two different groups of moment resisting frames, including sandwich infill panels with and wi