Creep And Reliability Analysis Of Long-Span Concrete-filled Steel Tubes Arch Bridge

With the improvement of manufacturing process,the construction capacity of large-span bridges in China has developed rapidly.With the increase of span capacity,the nonlinearity of structure has became more and more obvious.For the calculation and analysis of CFST arch bridges,the concrete creep as a material nonlinearity and the geometric nonlinearity of the overall structure are unavoidable problems in the analysis.The study of concrete creep has been going on for nearly a hundred years,but there is still no definitive conclusion.As a important branch of the creep,concrete-filled steel tube creep is even more so.For this paper,the deterministic analysis and uncertainty analysis of the creep behavior of CFST arch bridges under self-weight are studied separately.The main contents of this paper are as follows:(1)The creep mechanism,hypothesis and mathematical model of concrete are expounded and extended to the creep analysis concept and mathematical model of concrete-filled steel tube structure.The Monte Carlo stochastic finite element method for uncertain analysis,the Latin hypercube sampling and the sensitivity analysis method of Spearman rank correlation coefficient are introduced.(2)A three-dimensional ANS YS model of Maocaojie Bridge of a long-span concrete filled steel tube arch bridge is established,and the creep effect analysis of the bridge under the condition of 1000d-calculation-age completion is considered.The creep law of concrete filled steel tubular(CFST)is summarized from the aspects of stress and deflection in different time-history.The results show that with the increase of age,the stress of steel tube increases while the concrete stress decreases.The rate is consistent with the strain rate.The early rate is large,then it is gentle,and the creep is mainly developed within 500 days.(3)The creep model,geometry dimension and material characteristics are analysed.According to the sensitivity analysis results,the main factors affecting the deflection of the final value of the creep are summarized.The design,construction and operation are provided for reference,and the safety performance of the bridge is evaluated in the form of reliability.The results show that the uncertainty of creep model,steel tube and concrete elastic modulus are the main influencing factors,and the concrete elastic modulus is the most important factor.(4)The tangent stiffness matrix of beam element considering geometric nonlinearity is deduced,and the creep effect of concrete is simulated by the initial strain method.Based on Fortran self-programming,the plane beam element model was established for the Maocaojie Bridge.The logarithmic age division was divided and the variation data of 1000d-calculation-age creep effect was analyzed and analyzed.We concluded that for creep analysis considering geometric nonlinearity,the numerical difference is about 5%compared with that under dead dead.It is necessary to consider the creep effect under geometric nonlinearity.