Reinforced concrete structures are considered as bare frames in analysis and design process, including the main structural members such as beams, columns and shear walls. However, in the urban areas, structural frames are filled with masonry walls as acoustic and thermal insulation in the middle or peripheral areas of the buildings therefore they have not the same behavior as the empty frames. This research aims at investigating the effect of unreinforced masonry infill panels on the response of RC frames against the progressive collapse. For this purpose a micro based modeling approach is adopted for numerical simulation of the masonry infill panels and through a parametric study, the effect of influencing parameters is numerically investigated. Also an equivalent compressive strut model is proposed for macro modeling of masonry infill panels. The comparison between numerical and available experimental results confirms the reliability of the developed model. Finally, the developed macro model is used to investigate the influence of masonry infill panels on the progressive collapse resistance of reinforced concrete frames with different ductility capacity. It is shown that, under the progressive collapse phenomenon, the ductility of RC frame is the main effective parameter and masonry infill panel play an important and non-ignorable role in structural response

Keywords: progressive collapse, Infill panel, Compression strut, RC frame