Study On The Seismic Behavior And Vibration Reduction Of A Complex CFST Frame Structure

In this paper, a series of research work on a high-rise building of CFST (concrete filled square steel tubular) frame structure with dampers are carried out, which mainly includes nonlinear analysis of CFRT(concrete filled rectangular steel tubular) columns, shaking table test and nonlinear time history analysis of the structure, seismic energy dissipation using viscous dampers. The specific contents are as follows.1. The uniaxial steel stress-strain model in which biaxial stress and local buckling effects of steel tube are considered and uniaxial concrete stress-strain model of CFRT column are built, based on the analysis of existing material constitutive models of CFRT columns.2. A new type of beam-column element is built by the combination of the second order finite element flexibility method with fiber-model beam-column element. Simultaneously, several measures are provided to solve the problem that strange section stiffness matrix can not seek the inverse and improve the stability of the method. Additionally, the 3D nonlinear analysis program of CFRT frame structure is developed based on the element model and materials models suggested in this paper, which is verified by the comparison of the calculation results with the test results of 16 test models of CRFT columns. Finally, the simulation of CFST columns in high-rise building is carried out by the program to investigate its seismic behaviors.3. A 1/15 scale model of the high-rise building of CFST frame structure with dampers is tested on shaking table to investigate the dynamic characteristics and seismic response, especially the effect of dampers on seismic behavior of the structure. Based on the test results, the structural analysis model composed of multi-spring model of beams and columns is established, then the elasto-plastic time-history analysis for the shaking table test model of the structure is carried out, and good agreement between analysis and test results is obtained. Finally, the analysis for prototype structure is performed by the same procedure to study its seismic responses and yield mechanism. The analysis and test results show that the structure has no obvious weak story and can meet the code requirements for energy dissipation structures.4. A series of pararnetrical analysis of single degree freedom structure with viscous damper are carried out by a program developed in this paper. Based on the results of parametrical analysis, an optimum design method of seismic energy- dissipation structure is developed and two seismic energy-dissipation schemes with different inter-story drift reduction ratio of the CFST frame structure are designed by the method. By the analysis of the structure under the two optimum schemes and the other scheme with damper uniform installation, the seismic response of the structure with different energy-dissipation scheme at frequent and seldom seismic intensities is investigated.