Probability Statistical Analysis And Partition Study Of Temperature Gradient Of Steel Box Girder Based On Measured And Meteorological Parameters

Compared with concrete box girder,steel box girder is widely used in the construction and construction of various long-span bridges such as suspension bridges and cable-stayed bridges due to its lighter weight higher strength and more construction.The temperature gradient mode and its effect of steel box girder is one of the important foundations for the life-cycle performance design of steel box girder bridges.Due to the vast territory of China,which spans many climatic regions,it is affected by the climate of different regions The temperature effect of bridge structure in different areas has obvious regional differences.At present,the temperature gradient value of box girder in Chinese Bridge and culvert design code does not consider the regional differences.Therefore,it is necessary to study the value of temperature gradient mode of steel box girder in different regions of China,and divide the regions according to the different value of temperature effect.Based on the engineering background of Tuojiang 4th bridge in Luzhou,Sichuan Province and the Jiangdong Bridge in Hangzhou,Zhejiang Province,this paper studies the temperature effect of steel box girder by using the methods of temperature field simulation analysis,long-term measured data combined with probability statistical analysis,probability statistical analysis of temperature effect based on meteorological parameters and BP neural network The main research work and results are as follows:(1)sum up the research results of steel box girder temperature field at home and abroad,and determines the research content and technical route according to the deficiency of the research results.(3)long-term monitoring of the temperature field of the unpaved steel box girder was conducted to analyze the rule of temperature field of steel box girder over time;The temperature field distribution of steel box girder along the transverse bridge and vertical direction in different weather is given.By comparing the measured temperature with the theoretical calculation,the accuracy of the theoretical calculation is verified.(2)According to the finite element theory of steel box girder heat conduction and the power exponent calculation method of solar radiation model,the finite element model of temperature field of steel box girder of operational Tuojiang 4th bridge is established.By comparing the measured temperature with the calculated temperature,it is found that the difference between the two values is small,and the trend with time is basically the same,which verifies the accuracy of the finite element model.(3)Based on the long-term monitoring data of the temperature field of the steel box girder of Tuojiang 4th bridge,the probability density distribution of the daily maximum vertical positive temperature difference of the steel box girder is described by using the statistical analysis method,and the standard value of the vertical positive temperature difference of the steel box girder with a return period of 100 years is obtained on the basis of the Gaussian mixture model;the vertical temperature gradient distribution of the steel box girder is described by using the exponential function;finally,the temperature gradient distribution of the steel box girder of Tuojiang 4th bridge is obtained The vertical temperature gradient model of PK section steel box girder of operational Tuojiang 4th bridge.(4)Based on the measured meteorological data and actual bridge temperature data in Hangzhou area,an accurate calculation model of steel box girder temperature field of Jiangdong Bridge in operation stage is established.The meteorological data of sunny days and cloudy weather with long sunshine hours in summer of 2014-2016 in Hangzhou area are obtained through the Meteorological Bureau.Using the meteorological research results,it is transformed into a time history model of meteorological parameters,combined with the calculation model of steel box girder temperature field,The distribution of the daily maximum temperature difference between the top and bottom of steel box girder in this kind of weather in summer is obtained.Taking the daily maximum temperature difference of steel box girder in this kind of weather as the sample,the statistical analysis is carried out.After comparing the goodness of fit of several probability density functions,the generalized extreme value distribution is selected to describe the probability distribution of the daily maximum positive temperature difference of steel box girder of Jiangdong Bridge.Based on this,the vertical distribution of steel box girder with return period of 100 is calculated Standard value of positive temperature difference.The exponential function is also used to describe the vertical temperature gradient distribution of steel box girder,and finally the vertical temperature gradient mode of steel box girder in the operation stage of Jiangdong Bridge is obtained.(5)Use the BP neural network model to establish the mathematical relationship between the regional latitude,altitude,annual maximum temperature and the standard value of the temperature difference between the top and bottom of steel box girder in the area.The model is used to predict the standard value of temperature difference of steel box girder in 237 cities in China.The predicted value of standard value of temperature difference of steel box girder is concluded through analysis,China is divided into four regions to evaluate the temperature effect of steel box girder.