Seyfi Azar, A.Moradi Shaghaghi, T.2020-11-022020-11-022017-01-01Article in Journal of Fundamental and Applied Sciences Vol 09, N 011112-9867http://dspace.univ-eloued.dz/handle/123456789/7390Article in Journal of Fundamental and Applied Sciences Vol 09, N 01Steel box-shaped columns are suitable structural members for structures with moment frames in two directions, but plate connections have several construction problems, including inaccessibility of inside of columns, welding difficulties, etc. ConXL connections are the new proposed details to reduce these problems. This connection consists of collar flange, collar corner, and collar web extension. In this paper, the seismic behavior of these types of connections is investigated using the numerical method. For this purpose, three samples of ConXL connections without concrete filler, with concrete filler and with concrete filler and stiffener plates inside the column were studied using Abaqus software. The results demonstrated that the ductility of the ConXL connection without concrete filler is more than the two other samples, while the strength of this connection is less than the strengths of the two other samples. It was observed that utilizing stiffener plate inside the column has no significant effect on the strength of the connection.enConXL moment connection; collar; concrete filled steel tube (CFT); ductility; stiffener plate.Article