Experimental And Theoretical Research On Seismic Behavior Of Concrete-Filled Steel Tubular Frames

Mechanics performance for the members of concrete-filled steel tubular (CFST) structure has been studied in many countries at present. However, research on the working performance of CFST frame has seldom been reported. This thesis presents an experimental and analytical study on seismic behavior of CFST frame. The major contents are summarized as follows:An experimental research on seismic behavior of CFST frame was performed. The frame, which is designed following the current codes, can form the beam-hinged failure mechanism under lateral cyclic loads. The deformation capacity, bearing capacity, ductility and energy consumption are contest with the earthquake resistant design requests. Effective ductility factor of the frame model is 7.54, which is far bigger than the request value of the ordinary ductile frame. Based on the research result on the bending rigidity of CFST columns and "D" value method, the horizontal displacement of CFST frame structure is calculated, and the calculated values are much coincided with the tested values.The nonlinear finite element analysis on CFST frame is performed. Based on the characteristics about CFST, a constitutive relationship is put forward, which is suitable for CFST structures under cyclic loading. The regular pattern of rigidity degeneration of the CFST frame under cyclic loading was gained. Based on the uniform modulus theory and the separated modulus theory of CFST respectively, the mechanics performance of CFST frame in consideration of the influence of the nonlinearity of materials and geometry, and stiffened joints under cyclic loading were investigated by employing the command stream edited with ANSYS Parametric Design Language, and the calculated results are much coincided with the tested results, which proves that the design method for CFST structures based on the uniform modulus theory of CFST is feasible and practical.Seismic reliability of CFST frame is analyzed. The failure correlation of beam end and column end under "minor earthquake" was analyzed by Monte Carlo simulation method. Based on this, a reliability analysis method for CFST frame under "minor earthquake" is presented. Based the member model which is suited for frame structures analysis, a reliability analysis method for CFST frames under "server earthquake" is presented. The limit-state function is established by global damage indices. A seismic design method based on reliability theory for CFST frame is put forward. The resistance factor under the influence of the earthquake load variation and resistance variation is discussed. At last, the resistance factor and earthquake load factor for different important buildings are suggested. ...