The Seismic Retrofitting of Moment Connection Beam to Double-I Column by T-Stiffeners

In the present paper, the retrofitting of welded moment connections with welded flange plate (WFP) in Double-I built-up columns with overall cover plate is discussed by presenting the design method and retrofitting details. The problems of above-mentioned connection include the unfavorable quality of groove weld with full penetration at the connection of the flange plate and the column cover plate, or in worse conditions, using one-sided fillet weld with insufficient strength, the out-of-plane buckle of the column cover plate at the level of the beam-to-column connection, and as a result, its inappropriate seismic performance and its partially restrained behavior. Thus, it was tried to evaluate the advantages of strengthening this defective connection with the help of T- stiffeners using analytical and experimental studies. For this purpose, the experimental test and the finite elements model were made based on the proposed design method, and its cyclical behavior, rupture potential of weld connection, and failure mode under cyclical load were compared with the defective sample. The results indicated that the proposed design, while being classified in the group of fully restrained connections, has the necessary strength and ductility to accept the conditions of the special moment-resisting frame according to the AISC. By performing a sensitivity analysis on the T- stiffener by changing its dimensions and examining the damage indices, the accuracy of the proposed design method was proved. The examinations indicated that the aforementioned retrofitting method is a proper method for the introduced defective connection.