چكيده به لاتين
Due to the increasing use of concrete filled tube (CFT) columns in recent years, various details have been provided for connecting beams to these columns. These details are usually designed and executed using through bolts, blind bolts, or continuity plates (diaphragms). According to AISC 341 (2016), the use of internal continuity plates (internal diaphragms) with holes are permitted in the connections of beam to CFT columns. However, except in the regulations of Japan and China, there are no specific design requirements for this detailing. However, studies show that the relationships presented in these regulations sometimes are not accurate and there are limitations for using materials and dimensions of components. In the present study, we have tried to investigate the effect of using these continuity plates and their detailing on the ultimate strength of the connection and shear strength of the panel zone. For this purpose, various parameters such as the ratio of width to thickness of column flange (2γ), ratio of beam width to column flange width (β), beam depth to column depth ratio (η), beam flange thickness, continuity plate thickness and hole diameter, and non-geometric parameters such as the ratio of axial force to column’s axial capacity, and using different grades of steel and concrete materials, were considered. After validating the modeling results in Abacus software, the samples were classified into two groups to evaluate the ultimate strength of connection and shear strength of the panel zone. The specimens of the first group were designed to investigate the ultimate strength of the connection based on the criterion of strong column - weak beam and the specimens of the second group were designed based on the criterion of strong beam - weak column to investigate the shear strength of the panel zone and. In the specimens of the first group, in addition to investigating the effect of each of the introduced parameters on the ultimate strength of connection, the effect of the beam and column parameters on the participation of continuity plates in providing this strength was also investigated. In the specimens of the second group, the effect of changing the detailing of the continuity plate and changing the wall thickness of the column on the behavior of the panel zone and the degree of participation of each of these components in bearing the shear force was studied. In this study, the values of 28, 18, 13 and 9 were considered for 2γ, the values of 0.37, 0.556 and 0.741 for β and the values of 0.767, 1.1 and 1.43 for η. The results showed that the change of parameter β has a greater effect on the final connection strength and the degree of participation of the connection sheets in providing this resistance compared to other parameters. Also, in the range considered for the beam and column parameters in the present study, it can be suggested to use a hole diameter equal to one third to one-half of the column dimension for the connection sheets designed according to AISC 341 (2016). Also, the results obtained regarding the shear strength of the panel zone showed that the presence of the continuity plate does not directly affect the shear strength of the panel zone, but it will change the participation of these components in the bearing by creating confinement for concrete and transferring force to the walls of column.
