Analysis Of Mechanics Behavior Of The Concrete Filled Square Tube Column To I-shaped Beam With Penetration Bars

In concrete filled steel tube structure, the cross section forms of steel tube primarily include circle, rectangular, square, and regular polygon etc., among which circle and square tube have been widely applied to practical engineering project. Although confinement effect on concrete from square tube is obviously weaker than circle tube due to stress concentration, concrete-filled squre tube (CFST) have remarkable advantages of the more simple form, no space overlapping problems, larger cross-section flexural stiffness, better stability performance, easier fire prevention measures carried out so that recently it has been increasingly used widely. Frame joints are of great significance to the mechanical behavior, and it is necessary to ensure that the internal forces of beam end can be effectively transfered to the column. The requirements on the strength, stiffness, stability and seismic performance of the joints desgin must be reasonably satisfied. Compared with reinforced concrete beam, steel beam have the characters of higher intensity, lower quality, shorter construction period and easier to open hole. Therefore, the study on the composite joints with CFST and steel beam is of practical significance and has great potential development in the engineering field.Based on the previous experimental results of CFST to steel beam joints with penetration components, the mechanical behavior of CFST to beam joints with penetration rebar-an internal joint strengthened has been carried out. In this paper, with the consideration of geometrical, material and contact nonlinearity, the ABAQUS software platform is utilized to analyze the mechanical behavior of the joints by building FEM model. The main contents and conclusions in this paper can be briefly summarized as follows:(1) The FEM model and numerical results are validated to be good agreement with test results through modeling CFST-I shape steel beam joints under cyclic loading.(2) The study on improvement of performance of joints after inserting a plate that aligned with the girder web, are conducted and compared with connections stiffened by outside ring. The results show that the joints with penetration rebar can save more steel, construct more simply, have more explicit force transferring path and no limit to the column size. Moreover, the penetration web in steel tube can improve the hysteretic characteristics of the joints. So it suggests that joints with penetration rebar have more application value than connections with stiffening ring. (3) The sensitivity analysis and comparison indicate that the parameters of the axial load level of the CFST, the steel ratio of the tube and rebar strength have great influence on the bearing capacity and seismic behavior.(4) To study the improvement of web reduced beam used in joints on mechanical behavior, the orthogonal design method is adopted to design model plan to investigate the influence of related parameters on the ductility and energy dissipation. The optimized parameters are combined, providing instructive suggestions for structure design.