Reliability Analysis And Calibrition On Railway Bridges And Culverts

At present,the allowable stress method and safety factor method are still adopted in the design of railway concrete bridges and culverts in China.Although the limit state and reliability design method of railway bridges and culverts were studied in China as early as the end of the last century,and the unified standard for reliability design of Railway Engineering(GB 50216-1994)and the code for design on railway bridge and culvert(Limit State Method)(Q/CR 9300-2018)were issued,but the design method of railway bridges and culverts has not been substantially changed.This is not commensurate with the advanced level of China's high-speed rail technique development,and it is also very unfavorable for China's high-speed rail technology to go abroad.There are many reasons for the above situation,one of which is the lack of in-depth study on the probabilistic limit state design method of railway bridges and culverts,and there still exist some problems to be solved in the code for limit state design of railway bridges and culverts.In order to improve the probability limit design method of railway bridges and culverts and provide reference for the revision of railway bridges and culverts code,according to the requirements of the project of China Railway Corporation,this paper studies the reliability of railway bridges and culverts in China.The main contents and conclusions are as follows:(1)The railway bridge and culvert loads are studied and analyzed to determine the probability distribution types and statistical parameters of railway bridge and culvert loads;the standard value of wind load in 100 year return period and the statistical parameters of maximum value of wind load in 100 year design service life are determined;the mechanical properties and dimensions of the collected materials are sorted and analyzed to determine the material properties of railway bridge and culvert.The analysis shows that the average load of passenger and freight trains in the Code for train load diagrams(TB/T 3466-2016)is 1.057 times of the average value of the Zhong-live load;the statistical characteristics of the concrete performance in the railway industry are close to the analysis results of the construction industry.As a general structural material in China,it is suggested that the statistical parameters and strength standard values of concrete performance of railway bridges and culverts should be the same as those in construction field.(2)Based on code for design on railway bridge and culvert(Limit State Method)(Q/CR 9300-2018)and code for design of concrete structures of railway bridges and culverts(TB 10092-2017)and the newly collected statistical parameters of material performance,this paper analyzes the uncertainty caused by the calculation mode of member bearing capacity and the uncertainty caused by the design variable itself.Considering two kinds of uncertainties comprehensively,the statistical parameters and probability distribution types of resistance of axial compression members,axial tension members,eccentric compression members,flexural members and shear members of concrete railway bridges and culverts are determined.The results show that the bearing capacity of each member obeys the lognormal distribution.(3)Based on the design expressions and requirements of the code for design on railway bridge and culvert(Limit State Method)(Q/CR 9300-2018),considering the combination of "permanent load + train load","permanent load + wind load" and "permanent load + train load + wind load",the reliability of concrete railway bridge and culvert axial tension members,axial compression members,large eccentric compression members,small eccentric compression members,flexural members and shear members are analyzed.The analysis shows that for the above three combinations,the average reliability indexes of each member designed according to Q/CR 9300-2018 are 4.7634,4.5325,4.4001,5.1388,4.1091 and 7.5573 respectively;the average reliability indexes of each member designed according to TB 10092-2017 are 5.3915,5.6087,4.3018,6.2877,4.6845 and 7.0789 respectively.