Study On Mechanical Behavior Of Long-span Rigid Frame Concrete Arch Bridge

With the rapid development of arch bridge in China,long-span steel tube concrete arch bridge with stiff skeleton is widely used in the construction of mountain bridges in Chinamore and more.The main reason is that its advantages are applicable to the actual situation in China.However,the rigid skeleton concrete arch bridge has the characteristics of complex force,multiple system conversion times and various construction steps,so it is necessary to control the construction method and process.Therefore,in order to ensure that the final structural internal force state and linearity of the finished bridge meet the requirements,it is particularly important to establish finite element simulation model analysis.Combined with the relevant engineering practice background,this paper briefly describes the construction scheme and main construction steps of related projects.Combined with the construction process,the finite element simulation model is established by using the finite element software Midas/Civil,and the simulation method of the stiffness skeleton in the model and the application of the joint section in the concrete filled steel tube material in the construction stage are given.Through the unknown load factor method,the corresponding cable tension in the construction process is given.Finally,the internal force and deformation of the arch bridge in different construction stages are obtained by finite element simulation analysis,and the change law of the operation stage of the arch bridge is given by the calculation of material shrinkage and creep.The results of finite element analysis show that the material stress level of arch bridge meets the specification requirements.The stress variation of the arch ring along the horizontal direction,the outer steel tube and the concrete in the pipe are consistent with the inner stress variation law,and symmetrical along the midspan direction.The stress of upper chord varies greatly from that of lower chord,but it still keeps symmetry.The reason for the difference is related to the sequence of concrete construction.Because of the influence of concrete shrinkage and creep,the main influence on the rigid skeleton arch bridge is to increase the stress of steel tube and cast-in-place concrete,reduce the stress of cast-in-place concrete,but do not change the stress distribution along the bridge length direction.Therefore,designers should pay attention to the sequence of construction and shrinkage and creep of concrete.