Research On Seismic Performance Of Concrete-filled Steel Tube Tensile And Bending Members With The Initial Spherical Imperfection

With the advantages of superior mechanical performance,common construction,good economic efficiency and beautiful structure,the concrete-filled concrete truss girder bridge is widely used in engineering examples.Previous studies have found that structural members in actual engineering often work with defects,and the existence of defects can weaken the combined advantages of concrete-filled steel tube structures and reduce their mechanical properties.It is inevitable that a spherical crown-shaped void defect occurs in the lower chord of a concrete-filled steel tubular truss girder bridge.However,the research on such components is mostly static,and the seismic test research is still incomplete and needs further research.In this paper,the seismic behavior of circular steel tubular concrete members with spherical crown-shaped voids is studied.The specific work is as follows:(1)The review of the bending and hysteresis behavior of the concrete-filled steel tubular members and the research status of the voids are systematically reviewed,and the research results and shortcomings are summarized.(2)A total of 12 concrete tubular concrete-filled concrete members were subjected to hysteretic test,including 8 concrete-filled steel tubular specimens with spherical crown-shaped void defects and 4 non-empty steel-concrete composite specimens.The main parameters are:axial pull ratio,void rate.The effects of the above parameters on the seismic behavior of concrete-filled steel tubular specimens with spherical crown-shaped voids under combined bending and bending forces were studied systematically.(3)Based on the reasonable determination of the stress-strain constitutive of steel and concrete under the low-cycle reciprocating load,the circular shape of the spherical crown-shaped void is established by using the large nonlinear finite element software.Finite element model of concrete-filled steel tubular members.Afterwards,the feasibility and accuracy of the model were verified by simulation comparison of the test results of the predecessors and myself.(4)Based on the above-mentioned verified finite element model,based on the reasonable selection of typical examples,the important parameters such as void rate,axial pull ratio,material strength and steel content are analyzed systematically.The influence law of hysteretic load-displacement skeleton line of concrete-filled steel tubular members under action.