Research On Dynamic Reliability Of High-speed Railway Bridges Based On Subset Simulation Method

With the rapid development of railway bridge construction in China,as a highway transportation hub,bridge plays an increasingly important role.At present,the research on train-track-bridge system is mainly focused on the train,and there is relatively less research on the reliability of the track bridge system.After the time-varying effect is introduced,the research on the time-varying reliability of the track bridge is more scarce.Based on the above situation,the research of this paper mainly includes the following work:1.In this paper,the dynamic analysis model of axle system of pre-stressed box girder is established by ANSYS Software APDL,considering the randomness of the material,the track bridge and load model are established,and the algorithm program of Subset simulation method is compiled.2.This paper compares and analyzes the influence of the train speed on the vertical deflection of the bridge span in the general situation,that is,the dynamic response of the single row train through the pre-stressed box type bridge,and calculates the failure probability at different speeds by the subset simulation method.The influence of concrete elastic modulus and steel modulus on vertical deflection of bridge span is compared and studied.3.Considering the dynamic response of the bridge under adverse conditions,that is,the two-row train passing through the pre-stressed box Bridge,the influence of train speed,concrete parameters and steel bar parameters on the failure probability of the bridge is studied,and the failure probability of the bridge under different parameters is calculated by using the subset simulation method.4.Under the condition of long-term service,the development of concrete performance and pre-stress loss of bridge is analyzed and compared,and the time-varying reliability of bridge in different service years is calculated by using subset simulation method.The influence of the dispersion of concrete properties and steel bar properties on the time-varying reliability of bridges is studied.The following conclusions are obtained through the above-mentioned studies:1.Under normal circumstances,the deformation of the bridge caused by the dynamic load of the train is about one-tenth of the constant load deformation.Under adverse circumstances,the deformation of the bridge caused by the dynamic load of the train is about one-fifth of the constant load deformation.The vertical displacement of pre-stressed box girder span is very small under different train speed,which indicates that the vertical displacement of box girder is mainly affected by the properties of the material,not by the driving speed of the train.2.By using the subset simulation method,the influence of concrete parameters and steel bar parameters on the reliability of bridge under adverse conditions is calculated,and it is found that the dispersion of concrete elastic modulus has the greatest influence on bridge reliability.With the increase of variation coefficient of elastic modulus of concrete,the failure probability of bridge increases from 4.14×10-19 to 2.5×10-4.The dispersion of concrete density,steel modulus and steel bar density has similar influence on bridge reliability,and the failure probability is at 10-6 this level.3.The performance and pre-stress performance of bridge concrete decreases with the increase of the number of years of service but its development trend is consistent.The attenuation is mainly concentrated in the first two years of pre-stressed concrete bridge use and the bridge performance attenuation is fast in the first ten years.When the use period of concrete bridge is more than 50 years,the change tends to be flat.The change law of bridge vertical span displacement and bridge time-varying reliability is consistent with the change trend of bridge performance.4.Under the condition of long-term service,the influence of concrete parameters and steel bar parameters on bridge reliability is greater than that under the condition of not considering long-term service and the influence of concrete elastic modulus dispersion is the greatest With the increase of variation coefficient of elastic modulus of concrete,the probability of bridge failure increases from 1.28×10-18 to 2.74×10-4.The elastic modulus of steel bar is slightly larger than that of concrete density and steel bar density,and the influence of concrete density and steel bar density is similar.