The Study On Bending Performance Of Improved Special-shaped Concrete-filled Steel Member

This paper presents a combined special-shaped concrete-filled steel tube,the steel pipe is directly welded by rectangular steel tube and U-shaped steel tube.Compared with the special-shaped combined and multi chamber steel tube concrete,the new combined concrete filled steel tube has the advantages of easy fabrication.There is only a piece of steel which can save the engineering cost.The special-shaped CFST can not only satisfy the bearing capacity and aseismic requirements of the structure well,but also make room more beautiful and neat,the area of the building has been improved,so it has been widely used in practical engineering.In this paper,with the aid of the Special Fund for basic research projects in the Central Universities(WUT:2017-zy-056),the flexural performance of T and L-shaped concrete-filled steel tubular members is studied experimentally,and the flexural performance is analyzed by the finite element software Abaqus.The main research contents are as follows:(1)Through the experimental study on the flexural behavior of 18 modified composite T-shaped steel tubular members and 18 modified composite L-shaped steel tubular members,the experimental results show that the rectangular steel tube and U-shaped steel tubular members have uniform deformation,and can work well together.The damage form of the component is the tear crack of steel in tensile zone or drum buckling failure of steel in compressive region.(2)The influence of thickness,shear span ratio,concrete strength grade and axial compression ratio on flexural properties of steel tube is analyzed by experiment.The experimental results show that: for T-shaped concrete-filled steel tubular members,with the increase of the thickness of steel pipe,the flexural bearing capacity of the specimen is increased,and the flexural ultimate bearing capacity of the 4mm and 5mm members is increased by 18.4% and 40% compared with that of the 3mm thickness;With the increase of concrete strength,the flexural bearing capacity of the specimen is also increased,and the flexural ultimate bearing capacity of the concrete strength of C40 and C50 is increased by 9.9% and 20.4% compared with that of the C30;The shear-span ratio has little influence on the flexural ultimate bearing capacity of the members;The ultimate flexural capacity of the members is not a monotonous linear relationship with axial compression ratio,when the axial compression ratio is 0.4,the ultimate flexural bearing capacity is maximum,the ultimate flexural bearing capacity is substantially equal when the axial compression ratio is 0.2 and 0.6.For the L-shaped concrete-filled steel tubular members,with the increase of steel pipe thickness,the flexural bearing capacity of the specimen is also increased,and the flexural ultimate bearing capacity of the members with 4mm and 5mm thickness is increased by 18.6% and 44% compared with those of 3mm thickness;With the increase of concrete strength,the flexural bearing capacity of the specimen is also increased,and the flexural ultimate bearing capacity of the concrete strength of C40 and C50 is increased by 9% and 21% compared with that of the C30;The shear-span ratio has little influence on the flexural ultimate bearing capacity of the members;the ultimate flexural capacity of the member is not linear with the axial compression ratio,when the axial compression ratio is 0.4,the ultimate flexural bearing capacity is maximum,the ultimate flexural bearing capacity is substantially equal when the axial compression ratio is 0.2 and 0.6.(3)The nonlinear finite element analysis software ABAQUS was used to calculate the bending moment deflection curve of the components,and the test results were compared with the numerical simulation results to verify the rationality of the model established in this paper.