Study On The Construction Tolerance Of 700M Concrete-Filled Steel Tubular Arch Bridge

With the successful construction of the Pingnan Third Bridge,it has become possible to construct long-span CFST arch bridges.Academician Zheng Jielian has also stated that there are no technical difficulties in constructing a 700m-level CFST arch bridge,and considering factors such as economics and safety,it should be applied to engineering practice as soon as possible and promoted.However,the construction difficulty of a700m-level CFST arch bridge is greater and more likely to produce construction errors.Therefore,it is worth discussing whether the current regulations for the allowable error values are still appropriate.In order to highlight the differences of the 700m-level arch bridge,this paper relies on three other CFST arch bridges with spans distributed between340 m and 575 m to analyze and simulate the four arch bridges through theoretical analysis and numerical simulation.By comparing the differences in the effect of common construction errors on the static characteristics of the 700m-level arch bridge,the allowable value of construction errors for the 700m-level arch bridge is explored.The main research contents are as follows:The causes of common errors during the construction of CFST arch bridges are analyzed.Combined with the in-plane and out-of-plane unstable modes of the arch bridge,five types of deviations to be studied in this paper are determined.The displacement vectors of the in-plane and out-of-plane elastic unstable modes of the arch bridge are fitted with functions.The distribution forms of various deviation types on the main arch are described by sine functions with periods of π,2π,and 3π,and the influence of five types of deviations on the static characteristics of CFST arch bridges is studied by numerical methods.The minimum least-squares line relationship between the constant load pressure line of the actual bridge and the arch axis line is established through energy method,and the influence of high-elevation deviation on the bending moment should be based on the constant load pressure line of the actual bridge.The internal force expression of circular arch under any elevation deviation is deduced by force method,and its correctness is verified by example.Simplifying the arch in the plane and out of the plane as an equivalent compression member and introducing deviations,the equation of the compression member deflection curve satisfying the boundary conditions is solved to analyze the influence of in-plane and out-of-plane deviations on the stability of the arch structure.Based on this,the effects of different deviation peak values and types on the vertical deformation,axial force,bending moment,and eccentricity of the control section of four different-span CFST arch bridges are studied.The effects of five types of deviations and different deviation peak values on the elastic,geometric nonlinear,and double nonlinear stability safety factors of four differentspan CFST arch bridges are analyzed.The relationship between the double nonlinear stability safety factor,deviation peak value,and span under the influence of the most significant deviation type for spans ranging from 340 m to 700 m is established by calculating the results.The effects of the double nonlinear stability safety factor under single deviation and coupled deviation for the 700m-level CFST arch bridge are analyzed,and the suitability of the current regulations is discussed based on the calculation results.