Effective Length Factor Of Column In Sway Steel Frames With Reduced Beam Section Connections

Reduced beam section(RBS) connection can move plastic hinge outward from the beam and column interface to the beam in the earthquake. By trimming beam flanges, the plastic hinge will far away from the welds that have much fracture proneness due to stress concentration and welding sensitivity, reducing the possibility of brittle fracture of connections and improving the ductility of the structure with RBS connections. However, could increased the plastic rotation ability of the connection but weaken the stiffness, and influence the overall stability of the steel frame.At the present time, we usually analysis the stability of steel frame column take the place of entire steel frame in brief. When designing the steel frame column, the widely used method is the column effective length, it means using the effective length of column in stead of actual length to consider the relationship between columns and beams. The coefficient of column effective length can get from the value of its stability bearing capacity.In this paper, based on the column effective length theory of steel frames stability design and the parameter feature of arc-shaped dog-bone connection, through the method of change steel frame beam-columns linear stiffness ratio and the parameter of connection, we build twelve groups numerical model of the single-story and single-bay steel frames with arc-shaped dog-bone connection. After using the finite element software ANSYS to do the eigenvalue buckling analysis of the twelve groups single-story and single-bay steel frames with arc-shaped dog-bone connection, we can get the regular pattern between three parameters of arc-shaped dog-bone connection and the stability bearing capacity of steel frame column. Then under the consideration of steel frame initial defect, we take the mode to do the nonlinear buckling analysis under the different situation of sway frame and non-sway frame, so we get the parameter b and c, which represent the nonlinear buckling load regular pattern of sway frame and non-sway frame separately. After adjusted the section of beam and column, build the different modes of sway frame and non-sway frame with beam-columns linear stiffness ratio of RBS connection, then do the nonlinear buckling analysis, we can get the table of the coefficient of column effective length. The result of nonlinear buckling analysis shows that, the coefficient of column effective length of RBS connection steel frame increased a little, when compared with the regular connection steel frame column, no matter under the situation of sway frame and non-sway frame, and the amplitude between 0.02 and 14.16%.