Study On Stress Concentration And Fatigue Life Of Tubular Joints In Concrete-Filled Steel Tubular Arch Bridge

Concrete-filled steel tubular(CFST) arch bridge in China used more widely, but the fatigue life on CFST joints has not been given sufficient attention. Many experiments and theoretical study of the hollow steel tube (HST) joints are carried out availably in the off-shore structures; however, the research on the CFST joints inland and overseas is very few. In this paper, numerical analysis of the stress concentration factor (SCF) and stress distributions along the intersection of HST-CFST K-joints of CFST truss arch bridge were conducted. And the fatigue life of the joints on CFST arc bridge under vehicle load is predicted.Firstly, this paper introduces the basic concepts and methods which used in the fatigue analysis of the highway steel bridges, and summarizes the fatigue load spectrum inland and overseas and its study situation at present. Every fatigue life forecasting approach has its own characteristic, and it must choose appropriate method in the fatigue life analysis. In this paper, the method of fatigue life prediction is combining the hot stress approach and fracture mechanics approach.Secondly, 3-D finite element model of HST-HST and HST-CFST K-joints with the software ANSYS are established. And numerical analysis of the SCFs and stress distributions along the intersection of K-joints subjected to axial, in-plane bending and out-of-plane bending loadings is conducted. Because of the chord of the truss arc bridge bear extremely strong axial load, the paper analyses the influence of SCF and stress distributions of HST-CFST K-joints by axial load on chord in addition.Lastly, the analysis on the dynamical response of the CFST arc bridge under fatigue load of vehicle model are performed on the basis of three dimensional finite element model of the full-scale structure of the bridge, and three joints critical to fatigue damage are determined from the result of the dynamical response. The joints are applied displacement boundary conditions which conform to actual situation in local stress analysis. The formation life and expansion life of fatigue crack are calculated by the hot spot stress approach and fracture mechanics approach.Through the analysis of the fatigue life of the HST-CFST K-joints of a CFST truss arch bridge, it can give an example to fatigue strength analysis and fatigue life forecasting of the similar bridge.