Research On Refined Simulation Of The Temperature Field In The Tower And Girder Of Cable-stayed Bridges Based On Sunshine Shadow Recognition

The bridge structure is always exposed to the atmospheric environment.The temperature difference between the surfaces of the structure will be generated,including the overall temperature difference between the outer surfaces caused by the shadow shielding effect and the local temperature difference between the inner and outer surfaces in the wall thickness direction,under the influence of external environmental conditions(solar radiation,atmospheric temperature,and wind),thus forming an uneven temperature field inside the structure.Ignoring the temperature difference in the height direction of the structure,the two-dimensional analysis method is used to calculate the temperature field,which cannot accurately consider the influence of shadow occlusion.The calculated results obviously cannot reflect the real temperature field of the structure.At present,the provisions of the temperature gradient in the bridge codes of various countries are mostly concentrated on the main beam,and the differences between different codes are large,but the relevant provisions of the temperature field of the bridge tower are less involved.The temperature gradient distribution of the bridge tower is mostly considered according to the gradient mode of other similar projects,which may be quite different from the actual structure.Therefore,it is of great significance for the analysis of the temperature effect of the bridge structure in the construction and operation stages to accurately calculate the temperature field of the cable tower and the main beam structure under the action of sunshine and,on this basis,explore the temperature field distribution law.In this thesis,the temperature field of concrete girder and tower of cable-stayed bridge is studied.The parameter model verification,sunshine shadow recognition algorithm research,software development,temperature field analysis of concrete girder and tower of cable-stayed bridge are carried out.The relevant research results are summarized as follows:(1)The reasonable material parameters and thermodynamic boundary parameters are determined through literature research,and the accuracy of the daily temperature model and the solar radiation model is verified according to the measured data in the reference,which lays a foundation for the fine simulation of the sunshine temperature field of the bridge structure.(2)The real-time identification of sunshine shadow is realized based on ray tracing technology.Through the secondary development of Abaqus finite element software,a set of refined simulation methods for the three-dimensional temperature field of a bridge structure that considers the influence of shadow is finally formed and verified by measured data.(3)The sunshine shadow recognition results are successfully presented by improving the three-dimensional sunshine temperature field algorithm and combining the cloud image customization function in the post-processing program of the Abaqus software results,which is convenient for analyzing the shadow occlusion on different surfaces of the structure.(4)The parameter sensitivity of the temperature field calculation of a concrete bridge structure is analyzed using the developed three-dimensional temperature field fine simulation method.The results show that the solar radiation absorption coefficient has the greatest influence on the temperature calculation results,followed by the influence of wind speed change,and that the long-wave radiation absorption rate change on the structure surface has the least influence on the temperature field calculation results.(5)The distribution law of the temperature field of a concrete tower and beam is explored,using the concrete box girder and its tower of a cable-stayed bridge as a case study.The mode of temperature gradient distribution of the concrete tower and grider of the cable-stayed bridge is proposed based on the results of the temperature field analysis.(6)The temperature effect of the concrete bridge tower is analyzed based on a refined simulation of the temperature field of the bridge structure.A linear prediction method based on dynamic interval historical data is proposed for the linear shape of a concrete bridge tower during construction.The quantitative analysis results show that the relative change in tower top deviation at the beginning and end of the month caused by the change in solar radiation intensity is small within one month.