An investigation of the influence of semi-rigid composite column-beam connections on the seismic performance of a building with steel concentrically braced frames

Semi-rigid composite connections are connections which have a certain rotational stiffness and bending strength by means of slab concrete and reinforcement in column-beam joints. The use of these connections can lead to more economical sections, reduce deflection and vibration problems, and provide more efficient use of beam sections. Besides these advantages, these connections provide additional stiffness and strength to the structures. Therefore, they are permitted to be used as the primary systems in regions of high seismicity and as the secondary systems in regions of low to moderate seismicity. In this study, the effect of column-beam connections on the seismic behavior in the x direction was investigated in a building with special concentrically braced frames. For this reason, 3 building prototypes were created. In the first model, all column-beam connections are assumed as pinned connections. In the second building prototype, moment-rotation behavior of the column-beam connections (shear tab connections) are determined and are included in the analysis model. In the last building prototype, the interior frames and column-beam connections in the x-axis are designed as semi-rigid composite. In this way, the beam sections, which attached to the semi-rigid composite connections, have changed, but the other structural elements are the same as in Model 1. Nonlinear static analysis (pushover) was carried out and the seismic behavior was investigated. As a result, in BSE-2N and BSE-1N earthquake hazard levels, three models showed the same structural performance level. In the Model 3, which composite connections are used, it is observed that peak displacements are significantly reduced in cases where even base shear force is applied to the buildings and significant increases in the base shear strength are observed in cases where the equal peak displacements are applied to the buildings. In addition, when the actual behavior of the shear tab connections is included in the analysis, there are no significant differences between Model 1 and Model 2, and the models showed similar behavior.