The Refined Simulation And Field Measurement Of The Constructing Long-span High-speed Rail Continuous Box Girder Bridge Considering The Temperature Effects

With the rapid development of high-speed railways in China,the bridges in high-speed railways are becoming important.To ensure the stability and smoothness of high-speed railway lines,long-span bridges in high-speed railways are mainly concrete continuous box girder bridges.However,due to its own material properties,such as specific heat capacity and thermal conductivity,concrete continuous box girder bridges can cause concrete cracks or even structural damage due to temperature effects during construction and operation.Therefore,a concrete continuous box girder bridges in Yancheng-Nantong high-speed railway is taken as the example.With the combination of the field measurement and the finite element simulation,the temperature field and its effects during the construction of bridge is researched deeply.The main research contents are listed as follows:(1)Numerical simulation and field measurement analysis of the hydration heat of the zero block of the high-speed rail concrete continuous box girder bridge.Based on the principle of concrete hydration heat and the boundary conditions of concrete continuous box girder bridge in construction.A numerical model for hydration heat of the zero block of high-speed rail concrete box girder bridge is established using Midas,and simulating the hydration heat of concrete in construction.The simulation results are compared with the filed measurement for verification,and the temperature effect of the zero block is analyzed deeply.The results show that the simulation of the hydration heat of the zero block is well agreement with the filed measurement and the temperature stress of the bottom of the box girder is high.In project,cooling pipe is arranged in the bottom of the box girder to reduce the heat of hydration reducing the temperature effect.(2)Numerical simulation and field measurement analysis of the sunshine temperature field of a long-span high-speed rail concrete box girder bridge.According to the concrete structures theory a two-dimensional transient solar temperature field model of a high-speed rail concrete box girder bridge is established using ANSYS by combining the local meteorological parameters with the solar radiation semi-empirical formulas.The temperature field of the concrete box girder bridge under different weather is simulated and the simulated and measured results are compared.On this basis,the temperature gradient of the high-speed rail concrete box girder bridge is further simulated and compared with the temperature gradient given by different codes.The results show that the measured temperature of the box girder is well agree with the simulated temperature,and the temperature gradient based on the measurement fitting is similar to the recommended value in code(TB10092-2017).(3)Analysis on influencing factors of temperature field of long-span high-speed rail concrete box girder bridge based on numerical simulation.Using the established numerical model of the temperature field of high-speed rail concrete box girder bridge in sunshine,the values of parameters such as meteorological conditions,physical properties of materials,and cross-sectional shape are changed.The influence of factors such as solar radiation intensity,external ambient temperature,box room temperature,box girder height,top and bottom plate thickness,flange plate length,concrete thermal conductivity and specific heat capacity on the temperature field of concrete box girder is calculated and analyzed.The results show that the size of the concrete box girder has little influence on the temperature field of the high-speed rail concrete box girder,and has a slight influence on the local temperature distribution of the box girder.The length of the flange plate has a influence on the temperature distribution of the concrete box girder web,but it has little influence on the distribution of the maximum vertical temperature difference distribution of the high-speed rail concrete box girder.(4)Study on the temperature effect during construction of long-span high-speed rail concrete continuous box girder bridge.The whole process of cantilever construction of a high-speed railconcrete continuous box girder bridge using Midas,and numerical models are established for two working conditions.The temperature effect of the high-speed rail concrete continuous box girder bridge under the conditions is calculated based on the measured fitting and the temperature gradient given by the criterion.On this basis,the temperature stress distribution of the fulcrum section and the mid-span section of the the bridge is analyzed.The influence of sunshine temperature on the construction alignment of main girder is analyzed deeply.The results show that the bridge temperature effect calculated based on the measured fitting and the vertical temperature gradient given by the code(TB10092-2017)is relatively close.The temperature effect on the bridge under the two working conditions is small.The vertical displacement of the largest cantilever end in a day changes little at night and in the early morning.This time period can minimize the influence of temperature on the bridge alignment.