Research On Mechanical Behavior Of Concrete Filled Steel Tube Column To Beam Joints With Penetration Components Under Cyclie Loading

Recently, concrete filled steel tube (CFST) is more and more widely used in high-rise and long-span buildings because of its high bearing capability, excellent ductility and energy dissipation. Now mechanical properties of structural members have been researched systemically. Owing to the complexity and diversity of joints, research on the CFST joints is not intensive. Following the integrity of theory on CFST and widely used in engineering, joint of column to beam has become one of the key technical problems on the research and application of CFST. Therefore, mechnical properties of CFST joints with penetration components under cyclic loading were rerearched in this thesis. The main concents of this thesis include:(1) The experiments on eight joints of concrete filled circular steel tube (CFCST) column to steel beam with penetration components under cyclic loading are carried out, including 6 joints with penetration steel bars and the other 2 joints without penetration steel bars. Failure mode of joints is analysed. Ductility, energy dissipation and rotational stiffness of joints are attained.Based on the mechnical analysis and experiments, the formulas for predicting the flexural capacity at connections and shear capacity of joints are proposed. The calculated results of formulas agree well with the results of experiments, and also tend to be safe.(2) The experiments on six joints of CFCST column to reinforced concrete (RC) beam with penetration components under cyclic loading are carried out. Failure mode of joints is analysed. Ductility, energy dissipation and rotational stiffness of joints are attained.(3)The experiments on eight joints of concrete filled square steel tube (CFSST) column to steel beam under cyclic loading are carried out, including 6 joints with penetration steel bars and the other 2 joints without penetration steel bars. Failure mode of joints is analysed. Ductility, energy dissipation and rotational stiffness of joints are attained.Based on the mechnical analysis and experiments, the formulas for predicting the flexural capacity at connections and shear capacity of joints are proposed. The calculated results of formulas agree well with the results of experiments, and also tend to be safe.(4) The experiments on six joints of CFSST column to reinforced concrete (RC) beam with penetration components under cyclic loading are carried out. Failure mode of joints is analysed. Ductility, energy dissipation and rotational stiffness of joints are attained.(5) The experiments on fourteen high strength bolt-endplate joints of CFSST column to steel beam under cyclic loading are carried out. Failure mode of joints is analysed. Ductility, energy dissipation and rotational stiffness of joints are attained.The influence of high strength bolts, the thickness of endplate and the stiffening rib of endplate is studied. Yield load of endplate and high strength bolt is founded according to horizon force-endplate deformation hysteretic curve. According to the mechnical analysis and experiments, the formulas for predicting the type of high strength bolts and the dimension of endplate are proposed. Based on the research on shear capacity on joints of CFSST column to steel beam, and considering the contribution of the pre-tensioning force of high strength bolts, the formula for predicting shear capacity of high strength bolt-endplate joints of CFSST column to steel beam are proposed.(6) The experiments on six plain bolt-endplate joints of CFSST column to RC beam under cyclic loading are carried out. Failure mode of joints is analysed. Ductility, energy dissipation and rotational stiffness of joints are attained.According to the mechnical analysis and experiments, the formulas for predicting the type of plain strength bolts and the dimension of endplate are proposed. The calculated results are smaller than the results of experiments, and tend to be safe. Based on the research on shear capacity on plain bolt-endplate joints of CFSST column to steel beam, and considering the difference of high strength bolts and plain bolts, the formula for predicting shear capacity of plain bolt-endplate joints of CFSST column to RC beam are proposed.