A Numerical Investigation of the Influence of Semi-Rigid Composite Connections on the Seismic Behavior of a Building with Steel Concentrically Braced Frames

Abstract

Semi-rigid composite connections are connections which have a certain rotational stiffness and bending strength by means of the slab and its reinforcement. The use of these connections can lead to economic and structurally efficient solutions such as selecting smaller beam sections, reducing deflection and vibration problems. Additionally, they are permitted to use as a secondary lateral resisting system in regions of high seismicity. Therefore, in this study, two investigations were made in terms of seismic behavior evaluation: the influence of semi-rigid composite beam-column connections on interior frames and the influence of shear tab connections. Firstly, a 6-story building with steel special concentrically braced frames is designed according to current seismic design codes. Secondly, 3 models are created using the designed building. In Model 1, all beam-column shear tab connections are assumed as pinned connections. Model 2 and Model 1 are identical except that In Model 2, shear tab connections used in Model 1 are not assumed as pinned connections and their actual behavior is determined and included to the model. In Model 3, all beam-column connections on the interior frames are designed as semi-rigid composite connections. The interior frame sections are reselected and the exterior beam-column connections except for the ones on the braced bays are assumed the same as in Model 2. Lastly, nonlinear static analysis (pushover) is carried out and some comparisons are made with respect to the following aspects: lateral displacement and story drifts under same lateral force and lateral force under the same lateral displacement. As a result, Model 1 and Model 2 showed similar behavior due to the shear tab connections acting almost as pinned while Model 3 showed that using semi-rigid composite connections can increase the base shear capacity by %48 and decrease peak displacements and story drifts by %65.