Fatigue Reliability Assessment Of Orthotropic Steel Bridge Deck Under Random Traffic Flow Considering Parameters Correlation

Orthotropic steel deck has become a common type of bridge deck in the world because of its light weight,high material utilization,large bearing capacity and easy construction.At the same time,the fatigue cracking of orthotropic steel deck increases with the increase of traffic volume due to its special structure,numerous welds,concentrated stress at joints,and the direct bearing of wheel loads on the roof.How to establish the probability model of vehicle load in accordance with the actual situation is the basis for the in-depth study of the fatigue problem of orthotropic steel bridge deck subjected to wheel axle load.However,the existing vehicle load probability models are basically based on single factor,or simply integrate all factors together,without considering the possible interaction between the factors.Therefore,based on WIM data,this paper establishes a random traffic flow model considering the correlation of vehicle loads,and under the action of the random traffic flow model,the fatigue life of orthotropic steel bridge deck is analyzed and its reliability is evaluated,which mainly includes the following aspects:(1)Based on WIM monitoring data,a stochastic traffic flow model considering the correlation of traffic flow parameters is established.According to the fact that there are correlations among axle loads of vehicles in six provinces,such as Fujian,Guangxi,Hunan,Shaanxi,Liaoning and Sichuan,a correlation model of vehicle parameters based on Copula function is established;Based on this model,a stochastic traffic flow model considering the correlation of traffic flow parameters is established for traffic flow data of Nanxi Yangtze River Bridge.(2)A simulation method of fatigue stress spectrum of orthotropic steel deck under random traffic flow considering the correlation of traf fic flow parameters is proposed.In order to solve the problem that random traffic flow takes too long in stress analysis of-finite element model,a finite element model substitution method is proposed by using Latin Hypercube Sampling(LHS)and Kriging Response Surface Method,and a LHS-Kriging model for fast obtaining fatigue stress spectrum of orthotropic steel deck under random traffic is established.(3)The influence of random traffic flow considering the correlation of traffic flow parameters on fatigue life and fatigue reliability of orthotropic steel deck is studied.In order to ensure the fatigue safety level of orthotropic steel deck during the operation period,the detailed fatigue damage function of orthotropic steel deck under random traffic flow considering the correlation of traffic flow parameters was established.The effects of traffic volume growth and vehicle weight growth on detail fatigue life and fatigue reliability of orthotropic steel bridge deck were studied.(4)The time-varying reliability of fatigue crack propagation and propagation failure of orthotropic steel deck under random traffic flow considering the correlation of traffic flow parameters is studied.The fatigue reliability of orthotropic steel deck is evaluated by fracture mechanics.The first order Markov chain(FMC)model under random Ioad,the crack size growth formula under random load FMC and the failure function of orthotropic bridge deck detail crack growth are established.For the detail crack propagation failure of orthotropic deck is a small probability event,the cross-entropy method is used to estimate the failure probability.