Research And Prediction On Temperature Effect Of Long Span Prestressed Concrete Rigid Continuous Girder Bridge

The bridge structure is in the changing natural environment,but the thermal conductivity of concrete is poor.Under the influence of sunshine radiation,temperature and other external factors,the temperature stress will be generated in the structure,which will lead to the cracks and even damage of the bridge structure.Both theoretical and experimental studies show that temperature effect is one of the main factors affecting the stability and safe operation of the bridge.Therefore,in order to ensure the normal operation of the bridge,it is necessary to conduct a deep research on the temperature effect of the concrete bridge in order to better control and predict the adverse effect of the temperature effect on the bridge.In this paper,a large-span prestressed concrete rigid continuous girder bridge in Shandong is used as the engineering background.A large number of fiber grating temperature sensors,fiber grating strain sensors and force-balanced acceleration sensors are installed inside the bridge structure.Based on the long-term monitoring of the bridge structure,Data,analysis and research on the operating environment characteristics,impact and regularity of the bridge structure performance,the main work contents are as follows:(1)Taking the long-span prestressed concrete rigid continuous girder bridge as the research object,the sunshine temperature which has the greatest influence on the bridge structure is selected for analysis,and the temperature and temperature distribution law of different directions(longitudinal,transverse and vertical)and different sections of the bridge are studied.By comparing the merits and demerits of three methods,i.e.Foureir heat conduction method,approximate numerical solution method and semi empirical semi theoretical formula method,this paper decided to use semi empirical semi theoretical formula method to solve the temperature field of bridge box girder section.(2)The influence of bridge temperature effect on variation is studied.Considering the effect of strain lag temperature,the relationship between temperature and strain is predicted by using one variable linear function.Firstly,the temperature data is chosen as the input vector,the strain is chosen as the output vector,and the coefficient of determination is used to judge the goodness of fit.Secondly,the influence of the strain and the measured strain on the bridge after removing the temperature effect is compared and analyzed.Finally,the residual strain is used to judge whether the bridge is in the safe period.(3)According to the general situation of the bridge engineering,the finite element model of the bridge is established by ANSYS,and the structural modal analysis is carried out.The first six modal frequencies,modal shapes and other parameters are obtained.When studying the influence of bridge temperature effect on modal frequency,Kriging method is used to fit the relationship between temperature and modal frequency.Firstly,the temperature data are selected as the input vector,and the first 6-order vertical modal frequencies are selected as the output vector to calculate the error of the model and judge whether they meets the usage requirements.(4)BP neural network method is used to study the influence of bridge temperature effect on modal frequency.Firstly,the temperature data is selected as the input vector,and the vertical first 6-order vertical modal frequencies of the same time period is selected as the output vector.Different types of error values of this model are calculated.Compared with the Kriging model,a better method of fitting prediction is found.