| Concrete-filled steel tubular arch bridge has been applied more and more widely in China's infrastructure construction.The arch ribs of the upper bearing concrete-filled steel tubular truss arch bridge are formed by direct welding of steel tubes.Therefore,the fatigue problem of the joints of the concrete-filled steel tubular arch bridge is more prominent,and the fatigue life of the pipe joints of the concrete-filled steel tubular arch bridge must be paid attention to.A large number of effective experimental and theoretical studies have been carried out on air tube and air tube joints in Marine engineering.However,the fatigue studies on concrete-filled steel tube joints are very few at home and abroad.In this paper,the stress concentration coefficient of the concrete and empty pipe joints of a concrete-filled steel tubular truss arch bridge is analyzed numerically,and the fatigue life and fatigue damage of the arch bridge under the load of automobile and earthquake are predicted.Firstly,the basic theory of fatigue life research of highway bridge structure is introduced.The present research status of structural fatigue of highway Bridges at home and abroad is expounded.Therefore,two methods of fatigue study of circular pipe joints are confirmed: S-N curve method and fracture mechanics method.The crack initiation life of concrete-filled steel tubular joints is studied by S-N curve method,and the fatigue crack propagation life of concretefilled steel tubular joints is analyzed by fracture mechanics.Secondly,based on the large finite element software,the finite element model of the whole bridge of the concrete filled steel tube truss arch bridge was established.The stress state of the static model of the whole bridge was calculated and analyzed,and the three K-section steel tube concrete joints at different positions of the arch ribs were selected.Then,the three-dimensional solid model of K-shaped hollow pipe and concrete filled steel tube joints was established by local analysis software FEA.The applied loads and boundary conditions were in line with the actual engineering conditions.The hot spot stress concentration coefficients of three K-shaped steel pipe concrete joints under axial loads and in-plane bending moments were calculated respectively.Then,on the basis of the three-dimensional finite element model of CFST trussed arch bridge and its dynamic response under fatigued vehicle load,the local hot spot stress analysis for selecting the position of fatigue joints is carried out.According to the hot spot stress concentration coefficient,the fatigue crack formation life and crack propagation life of the joint are calculated respectively by combining the S-N curve hot spot stress method and fracture mechanics.The fatigue life of the joint is obtained by combining the two factors.Finally,the fatigue life of CFST joints under different loading conditions and different peak seismic accelerations are analyzed.The damage caused by earthquake is equivalent to the traffic volume of fatigued vehicles to evaluate the impact of earthquake on concrete-filled steel tubular arch Bridges.In order to help people to estimate the fatigue strength of the key structure of the concrete-filled steel tube arch rib during the operation of the bridge after earthquake,and to provide reference value for the management and maintenance.Through the analysis of the fatigue life of the K-joints of the concrete-filled steel tubular truss arch bridge,some reference schemes are provided for the fatigue life prediction of this kind of bridge in the future. |
PDF Full Text Request