Investigation of the effects of Retrofitting the Connection of Steel Beam to Concrete-Filled Steel Tube Column with Bidirectional Bolts by Haunch plates

So far, a lot of research has been done on concrete filled tubes (CFT) columns and their connections in different countries and several alternatives have been proposed for their connections, however, most of the proposed connections are associated with executive problems and have not been able to create rigid connection conditions. For steel moment frames that columns are of CFT type, new and suitable methods have been proposed to improve the behavior of their fixed connections. Among them are bidirectional bolted connections that in this study, the effect of strengthening this type of connection using haunch plated is surveyed. In these models, the main variables are haunch plates and column plate thickness. The results showed that by examining the formation of the position of the plastic hinge, it can be said that in the model without the haunch plate, plastic hinges and maximum strains are formed almost at the connection and on the face of columns. In most models retrofitted by haunch plates, however, the location of plastic hinge is in the off-connection area, approximately 20 cm side of the column. It has been seen that the CFT connections retrofitted by haunch plates, energy absorption has increased by 22.62% and the moment capacity bearing has increased by 3%. In addition, increasing the thickness of the column plate in the retrofitted connection has a greater effect on increasing the bearing capacity and energy absorption than increasing the thickness of the haunch plate.