| Bridges play an important role in highway transportation and social development,especially long-span bridges,which have important social significance and strategic position.Therefore,it is necessary to study the pylon to ensure that the bridge structures are in a balanced state.With the development of the transportation industry,the span of cable-stayed bridges has become much longer,and the structure has become more light ‘light’ and ‘flexible’.Therefore,the influence of geometric nonlinearity and material nonlinearity should be considered in the bearing capacity analysis of cable-stayed pylon.In the finite element analysis,the secondary internal force caused by geometric nonlinearity can be called the second-order effect.In the design stage,the eccentricity magnified coefficient is usually used to account for the influence of the second-order effect.To ensure the safety of super-long-span cable-stayed bridge pylon and explore the mechanical properties of the spatial diamond-shaped pylon,this paper makes numerical analysis and theoretical research on the eccentricity magnified coefficient and stability safety factor of the pylon,which mainly includes the following four parts:Based on the numerical analysis method,the eccentricity magnified coefficient of the pylon is studied.Taking Changtai Yangtze River Bridge as the engineering background,the bridge finite element model is established through MIDAS/CIVIL in this paper.According to the envelope diagram under the combined action of dead load and live load,the control sections of the pylon and corresponding adverse conditions are determined.According to the calculation method proposed in this paper,the eccentricity magnified coefficient of the pylon is calculated and analyzed,and the coefficient of pylon has considered the influencing factors such as construction deformation,geometric nonlinearity,initial defects,concrete shrinkage and creep effects;Secondly,based on the specification method,the eccentricity magnified coefficient of the pylon is calculated and compared.According to the specification formulas,the specification results of the eccentricity magnified coefficient of the pylon are obtained,and the specification results are compared with the numerical analysis results.Due to the bridge specifications of China,the US and Europe adopt different calculation methods in determining the eccentricity magnified coefficient,and the parameters and their values in specification formulas are different,there is a big difference in eccentricity magnified coefficient calculated based on different specifications.It is suggested to use the finite element method to analyze the eccentricity magnified coefficient of the pylon,and the specification method can be used as an auxiliary verification method to ensure the rationality of the concrete reinforcement design of the pylon;Then,the nonlinear analysis of structure is conducted based on OpenSees.The material constitutive model,section model,element model,convergence criterion,and solution method of the general platform software OpenSees nonlinear analysis are introduced in detail.The element types and element integration methods are summarized and compared.The nonlinear behavior of frame-reinforced concrete structures is simulated by OpenSees,and the results are discussed.The results show that the nonlinear behavior of the pylon can be effectively simulated by OpenSees analysis with stress element as calculation element;Finally,the nonlinear stability of cable-stayed bridge pylon is analyzed through OpenSees.The material constitutive model,fiber section model,and element type used by OpenSees in nonlinear stability analysis of cable-stayed bridge are discussed.Simultaneously,considering the material nonlinearity and geometric nonlinearity,the stability analysis of bridge pylon is carried out,and the results are demonstrated.The results show that the minimum stability safety factor of double-nonlinear stability of Changtai Yangtze River Bridge can meet the requirements of engineering design.The failure mode is mainly related to the cross-sectional bearing capacity,and when the failure occurs,the concrete in the compression area at the bottom of the pylon is crushed first. |
PDF Full Text Request