The 3-D Nonlinear Finite Element Analysis Of Concrete-filled Rectangular Steel Tubular Frame

CFRST has convenient connection, flexible architectural design, speed construction and other advantages, so has been extensively applied at world and achieved a good overall economic and social benefits. Relevant data show that compared with reinforced concrete, CFRST as beams can significantly improve ultimate flexural strength,ductility, stiffness and reduce the cross-beam deflection, and applied to the frame structure, can be effective in reducing story height, increasing the span. As such, in the paper, based on the experiment on seismic behavior of a 1-span,2-story CFRST frame under lateral cyclic loads,a 3-D nonlinear finite element model of CFRST frame is proposed by finite element software ABAQUS. The mechanical mechanisms and failure modes of CFRST frames were analyzed by ABAQUS. Research contents are listed as follow:(1) To the CFRST mechanical characteristics, through theoretical analysis and trial, rationally define steel and concrete constitutive relation under the static load and cyclic loading . Using the constitutive relation, the CFRST beam and CFRST column of literature [33][34] are studied. the results showed that the constitutive relation is correct and feasible.(2) Based on the experiment on seismic behavior of a 1-span,2-story CFRST frame under lateral cyclic loads, a 3-D nonlinear finite element model of CFRST frame is proposed by finite element software ABAQUS.This model takes into account the effect of the material and interface nonlinear and the stiffness degradation of concrete under cyclic loads. The calculated results by ABAQUS agree well with experimental results. The mechanical mechanisms and failure modes of CFRST frames were analyzed by ABAQUS.(3) Parametric study of load to displacement curves of CFRST frames were carried out based on the analytical methods in this paper. The steel ratio of the column and beam section, concrete strength,steel strength, axial load level of column, slenderness ratio, stiffness ratio of beam to column, were all considered as analysis parameters. They may be referred for design of CFRST frames.