Initial rotational stiffness of semi-rigid connections in steel column-tree moment-resisting frames

The theoretical calculation,experimental research and numerical analysis were conducted on two beamcolumn connections with cantilever beam splicing( fully splicing connection and flange welded-web bolted connection). The semi-rigid behavior was studied for joint region and splicing area. The stiffness characteristics and calculation model of initial rotational stiffness were discussed for semi-rigid connections in steel column-tree momentresisting frame. The structural probabilistic sensitivity analysis was conducted for the two beam-column connections with cantilever beam. A new calculation model including geometric parameters for the initial rotational stiffness of the beam-column connections with cantilever beam was proposed. The results show that the two beam-column joints and fully welded joint have semi-rigid characteristic; when the splicing area has sufficient strength,the initial rotational stiffness of the two beam-column connections with cantilever beam are in good agreement with the initial rotational stiffness of fully welded joint within the elastic range of the connections and the mechanical behavior of beam-column connections with cantilever beam and fully welded joint are relatively close within the elasto-plastic range of the connections; the effect of key parameters on the initial rotational stiffness can be clearly reflected in the model. The calculation example shows that,semi-rigid design is safer than rigid design with considering shear deformation in joint region for steel frame design; it is more accurate to do semi-rigid design with the calculation model of the initial rotational stiffness for the semi-rigid connections in steel column-tree moment-resisting frame.