Study On Flexural Behavior Of Three-Limb Curved Concrete-Filled Stainless Steel Tubular Truss

The three-limb curved concrete-filled stainless steel tubular truss structure has the characteristics of reasonable stress,large stiffness,strong deformation resistance,good integrity,etc.,and has superior durability and aesthetics.It has a wide application prospect in large-span,large-space,high-aesthetic needs exhibition halls,gymnasiums,bridges and other large-scale projects.At present,there is still a lack of research on this kind of structure at home and abroad,which restricts its promotion and application.In this paper,the flexural behavior of three-limb curved stainless steel tube concrete truss is studied.The main research contents are as follows:(1)The flexural mechanical properties of 8 three-limb curved curved concrete-filled stainless steel tubular trusses were studied.The effects of curvature coefficient,whether the upper and lower chords are filled with concrete,the type of steel tube material and the bearing capacity of the upper and lower chords on the failure mode,flexural capacity and flexural stiffness of the three-limb curved curved concrete-filled stainless steel tubular truss were investigated.The test results show that the flexural capacity,flexural stiffness and ductility of the truss with concrete-filled stainless steel tube are significantly improved compared with the empty stainless steel tubular truss.The flexural capacity and stiffness of the truss increase with the increase of the curvature coefficient,but when the curvature coefficient of the truss increases to a certain value,the local failure of the shear span occurs,and the bearing capacity and stiffness decrease.Compared with ordinary concrete-filled steel tubular truss,concrete-filled stainless steel tubular truss has the advantages of high later strength and strong deformation ability.The test specimen is controlled by the tensile bearing capacity of the lower chord,and the truss shows the failure of the lower chord.When the size of the upper chord decreases,the axial compression bearing capacity of the upper chord plays a controlling role,which is converted into the failure of the upper chord..(2)The finite element analysis model was established,and the flexural mechanism of the three-limb curved concrete-filled stainless steel tubular truss was analyzed.The failure mode and force transmission path of the truss were studied,and the stress-strain distribution and development of each component of the truss under different failure modes were studied.The parameters affecting the flexural mechanical properties of this kind of truss under various failure modes are analyzed.The influence of curvature coefficient,height-span ratio,chord-web angle,section height-width ratio and whether the upper and lower chords are filled with concrete on the flexural capacity and flexural stiffness of the three-limb curved concrete-filled stainless steel tubular truss is obtained.(3)On the basis of theoretical analysis,the calculation formula of flexural bearing capacity of straight concrete-filled stainless steel tubular truss is put forward,and the calculation method of axial compression stability bearing capacity and tensile bearing capacity of concrete-filled stainless steel tubular chord in the formula is determined.On this basis,the parameter analysis of the flexural bearing capacity of three-limb concrete-filled stainless steel tube truss with different curvature coefficients under two failure modes is carried out,and the calculation formula of flexural bearing capacity of three-limb curved concrete-filled stainless steel tubular truss is proposed.(4)The analytical solution of the deflection calculation formula of the three-limb curved concrete-filled stainless steel tubular truss considering shear deformation under the action of four points is derived.On this basis,the influence of the common curvature coefficient and other parameters of the truss is considered,and the vector angle in the formula is simplified.By studying the influence of curvature coefficient,height-span ratio and whether the upper and lower chords are filled with concrete on the bending stiffness of the truss,the flexural stiffness of the truss at different stress stages is corrected,and the corresponding vertical deflection calculation method of the three-limb curved concrete-filled stainless steel tubular truss at different stress stages is obtained.