Behavior Of Concrete Filled L-shaped Stiffened Steel Tubes Under Axial Compression

By means of the axial compression test and the finite element method(FEM),L-shaped concrete filled steel tubular(CFST)short columns without and with different longitudinal stiffener setting were studied in this paper.The best way of setting the longitudinal stiffener was choosed through analyzing the experimental results and the theoretically results.The FEM was used to simulate the optimum longitudinal stiffener setting member which taking the actual size of engineering structure,and the parameters which will influence the axial mechanical behaviors were also been analyzed.Finally,the simplified calculation formulas for axial bearing capacity of L-shaped normal and stiffened CFSTs were proposed.The main achievements were presented as follows:(1)2 L-shaped CFSTs without longitudinal stiffeners and 6 L-shaped CFSTs with different way of longitudinal stiffeners setting specimens were designed,and an axial compression experimental study was conducted on these specimens.By comparing the failure modes and the test data curves,the experiment results show that setting longitudinal stiffeners can enhance the ultimate bearing capacity and ductility of L-shaped CFSTs,and the different way of longitudinal stiffeners setting had a certain influence on the compression mechanics behavior of L-shaped CFSTs.(2)Taking the FEM of CFST members under axial compression of scholars at home and abroad as reference,8 L-shaped CFSTs(2 without ribs and 6 with ribs)were modeled and calculated by ABAQUS,the correctness of the modeling method was verified through comparing the buckling form and the load-longitudinal strain curves between experiment and calculate results,and the axial working mechanism of 8 specimens were analyzed.The results show that,setting longitudinal stiffeners can effectively improve the confinement on the core concrete of steel tube,as to the discontinuous longitudinal stiffeners setting specimens,the larger the interval is,the weaker the confinement is.Setting longitudinal stiffeners at reentrant corner can certainly improve the confinement on the core concrete of reentrant edge,and promote the longitudinal stress of concrete.(3)Explore the similarities and differences of the axial working mechanism of L-shaped CFSTs under different way of longitudinal stiffeners setting,combined the test results and the FEM results,area of longitudinal stiffeners and convenience of engineering construction,the optimum way of longitudinal stiffeners setting between the 6 methods introduced in this paper was choosed.(4)The FEM was used to simulate normal L-shaped CFSTs and the optimum longitudinal stiffener setting member which taking the actual size of engineering structure,the buckling form,load-longitudinal strain curves of the whole process,longitudinal stress of concrete and steel at each stage,and the lateral pressure of each edge of L-shaped steel to concrete have been investigated.Also,the parameters,such as concrete strength,wall thickness of steel pipe,steel strength and length-width ratio which will influence the axial mechanical behaviors were also been analyzed.(5)Taking the bearing capacity of the standard formula and papers about the bearing capacity of special-shaped CFSTs as reference,the simplified calculation formulas for axial bearing capacity of L-shaped normal and stiffened CFSTs were proposed.The simplified calculation formula was used to calculate the ultimate bearing capacity of the test specimens both in this paper and other scholars' paper,the correctness and applicability of the proposed formula was verified.