The Theoretical And Test Studies On The Load-carrying Capacity In Integral Stability Of Axial Compressed Cut T-shape Columns

Regulations for the load-carrying capacity in integral stability of axial compressed cut T-shape columns in the Code for Design of Steel Structures (GBJ17-88) are revised in a new version of the Code (GB50017-2003 ). According to GB50017-2003, the stability of the circling section symmetrical axis is flex-torsional buckling for the monosymmetrical section subject to axial compression. To promote the utilization of cut T-shape columns, it is necessary to further verify the rationality of the amendment through experiment.This dissertation discribes a theoretical study on the load-carrying capacity in integral stability of axial compressed cut T-shape columns: Firstly, the flexural buckling and flex-torsional buckling modes of axial compressed cut T-shape are presented. Secondly, theoretical analysis show that the major factors influencing the inelastic load-carrying capacity in integral stability are initial bending,initial eccentricity and residual stress. Finally, the equivalent slenderness ratio according to the Code (GB50017-2003 ) for flex-torsional buckling is derived. To verify the the rationality of the theoretical deduction, axial compression test and relative material test of three different sections with each section having five varied slenderness have been adopted in the Structure Laboratory of Xi'an University of Architecture & Technology. A lot of linear and nonlinear FEM(finit element method) analysis considering residual stress and initial defect have been carried out in terms of the material test results. Through the FEM analysis , corresponding buckling patterns , buckling strength and loading- placement curves are gained. These patterns and curves correspond to the above theoretical analysis and test study.Through the above three studies ,it is conclued that the way of GB50017-2003 calculating flex-torsional buckling is roughly correct and can ensure security, but it is conservative. Furthermore, it is recommended to limit the width-thickness ration for members of small slenderness.