Analysis Of Concrete Filling Process In The Tube Of Long-span CFST Arch Bridge

With the development of transportation industry,concrete-filled steel tubes arch bridge has been widely used in our country.For concrete-filled steel tubes arch bridge,concrete pouring in the pipe is an important construction process,and the key step to complete force transformation for structure,which has a certain impact on the stiffness and bearing capacity of the arch rib after the completion of the bridge.In this thesis,the mechanical properties of the concrete pouring process in the main arch ring pipe are analyzed based on the case study of the Daxiaojing Bridge project.The main work and research contents are as follows:(1)Mechanical properties are studied in the process of pouring concrete in single pipe strings of main arch rings.With MIDAS software modeling,the perfusion process is divided into 32 small conditions,among which it is about is about 7m for the horizontal perfusion length of each working condition.The calculation results show that in the process of single string tube perfusion,stress of the steel tube is far less than the allowable bearing capacity,and the vertical and lateral displacements of the structure are small and controllable.It is shown that the vertical and lateral displacements of the structure are small and controllable,indicating that the concrete filled steel tube arch bridge with a span of 450m,and its two sides are symmetrically and evenly filled,the concrete filled in the pipe can be completed without auxiliary measures(such as cable and pressure).(2)By using the finite element model of steel tube and concrete,the perfusion sequence of tubular concrete of long-span concrete-filled steel tube arch bridge is studied,and the evaluation index of perfusion sequence of concrete is put forward.Five common concrete pouring within tubes are analyzed and compared from the perspective of structure stress and deformation.The calculation results show that the perfusion sequence of lower chord followed by upper chord,inner chord followed by outer chord,and left and right chord tubes alternately is the most reasonable.Besides,the displacement change of the structure is relatively small and uniform,the compressive stress on the steel tube is smaller,and the compressive stress on the concrete within its allowable range is larger,Which is more beneficial to the stress on the bridge state.(3)The influence of sunshine temperature,hydration heat temperature in the process of concrete pouring in the pipe was studied.Theoretical analysis was made on the effect of integral rise and drop in temperature and single pipe rise and drop in temperature of structure in different perfusion stages,and the influence of sunshine temperature and hydration heat temperature was measured and analyzed.Research results show that the temperature of sun and hydration heat have a greater influence on structure than the concrete effect of the load.Therefore,the influence of sunshine and the temperature of hydration heat must be excluded in the stress and deformation evaluation of concrete perfusion process.The influence of temperature of hydration heat can be basically ignored three days after the completion of concrete perfusion in the pipe.