Analysis Of Long-term Deformation And Stress Redistribution Of Long-span Continuous Rigid Frame Box Girder Bridge

With the continuous growth of China’s inland economy and the development of infrastructure,continuous rigid frame bridge is widely used in ups and downs,majestic and dangerous terrain because of its large stiffness,low cost,convenient maintenance,strong leapfrogging ability,small deformation and so on.However,in the process of long-term development of continuous rigid frame bridge,problems such as deflection change away from expected deflection and irregular stress development are gradually presented to people.This paper will take Liexi large bridge as the engineering background and establish a relevant model with the help of finite element software.in view of the above problems,the deflection of the main beam,the long-term change of stress and the redistribution of concrete stress are analyzed and studied in detail.The specific contents are as follows:(1)The Midas Civil model is established to modify the parameters of the bridge from the aspects of prestress loss,closure deviation,bulk density,maintenance age and so on,and its long-term deformation is discussed.The results show that the prestress loss and bulk density have great influence on the deflection and stress,the closure deviation mainly affects the deflection,and the curing age has little effect on the deflection and stress.(2)Based on the relationship between the theoretical thickness of members and the shrinkage and creep of concrete,it is determined that there is mainly non-uniform shrinkage effect between the top and bottom plates of box section,and the temperature gradient expression of non-uniform shrinkage effect of box girder is deduced.it is applied to the finite element model of Liexi Bridge to discuss and analyze the long-term deformation under the effect of non-uniform shrinkage.For the factors related to non-uniform shrinkage effect in long-term operation of bridges,such as environmental relative humidity and concrete shrinkage period,the relationship between non-uniform shrinkage effect and non-uniform shrinkage effect is discussed.and the influence on the process of long-term deformation and non-uniform shrinkage effect of continuous rigid frame bridge.(3)Midas Civil and BR analysis models are established respectively.Firstly,the stress calculation results of the two models are compared and verified,and then the stress redistribution phenomenon of continuous rigid frame bridge is studied from the aspects of whether there is ordinary steel bar and reinforcement ratio.The results show that the stress value will be reduced by containing ordinary steel bar and increasing reinforcement ratio.Finally,the non-stress shrinkage and non-stress shrinkage and creep strain values in BR analysis is used to correct the measured strain value in the project site.(4)The formula of the internal force redistribution of the box section under the stress redistribution is derived by using the internal force distribution method.after calculation,it is found that the concrete of the box section will produce tension under the internal force redistribution,which is not conducive to the development of the member.The humidity diffusion of internal concrete in box section is simulated by ANSYS,and the formula of non-uniform shrinkage self-stress is deduced.after calculation,it is found that the resulting non-uniform shrinkage self-stress is tensile stress at the top and bottom of the section and compressive stress at the web,which has a great influence on the overall stress change of box girder section.