Stiffeness And Bearing Capacity Studies Of K-shape Intersecting Joint Concrete Filled Steel Tubulur(CFST) On Arch Rib

In the process of pumping concrete,the concrete of CFST arch bridge has not yet solidified to form effective bearing capacity.At this time,the self weight of CFST and flowing concrete will cause greater stress in the joint,which is prone to buckling failure of the branch pipe.At present,the research on the bearing capacity of the intersecting joint at home and abroad focuses on simplifying the joint into a bar element or only considering the influence of the plane load,which is different from the actual engineering.In addition,the influence of flowing concrete pressure on the bearing capacity of joints is rarely considered in the research.Therefore,in this paper,the stiffness and bearing capacity of K-joints of arch ribs are studied based on the engineering background of Guangxi Pingnan third Bridge,and the influence of flowing concrete pressure in the pipe on the bearing capacity of joints is discussed as follows:Firstly,the deformation behavior,failure mode and ultimate bearing capacity of K-joints are obtained by monotonic elastic load scale test under the combined action of axial force,in-plane bending moment and out of plane bending moment and monotonic static load scale test under the action of single branch pipe axial compression.Secondly,the orthogonal test method is used to determine the specific parameters of the calculation model,such as the clamp angle of the main pipe,the diameter ratio of the main pipe,the ratio of the outer diameter of the main pipe to the spacing of the branch pipe,the diameter thick Ness ratio of the main pipe,the ratio of the outer diameter of the branch pipe to the wall thick Ness of the main pipe,etc.the ABAQUS finite element software is used to analyze the calculation model,and the multiple linear regression method is used to fit the stiffness of the K-joints The accuracy of the fitting formula is verified by experiments and finite element analysis.Thirdly,the finite element analysis method is used to analyze the influence of the ultimate bearing capacity,mechanical performance and failure mode of the arch foot joint when there is pressure or no pressure in the pipe.And through the parameter analysis,under the pressure of a single branch pipe,the influence of the pressure in the pipe on the bearing capacity of the joint.The results show that the fitting formula is in good agreement with the experimental results and the finite element analysis results,and the error is within the allowable range,which verifies the accuracy and applicability of the fitting formula.The fitting formula can be applied to the structural design of arch rib joints,such as the simplified treatment of rigid or semi-rigid joints,and provide the research basis for the influence of local deformation of arch rib joints on the whole arch bridge.When considering the pressure of flowing concrete in the pipe,because the pressure in the pipe has a certain restraining effect on the deformation of the main pipe wall,the more obvious the local deformation of the pipe wall is,the more significant the restraining effect is.Compared with the effect of the pressure in the pipe,the ultimate bearing capacity of the arch rib joint has a certain increase;when the axial pressure is applied to a single branch pipe,the greater the pressure in the pipe,the thinner the main pipe wall is,the more obvious the ultimate bearing capacity of the joint is.