Study On The Fatigue Stress Spectrums And Fatigue Life Prediction Of Longitudinally Connected Ballastless Track On Bridge Under Combined Loads

Abstract:Fatigue under combined loads may happen in longitudinally connected ballastless track on bridge. People at home and abroad have carried out some researches on the fatigue characteristics of ballastless track,but little to the fatigue stress spectrums and the fatigue life prediction of longitudinally connected ballastless track on bridge under combined loads.So,researching the fatigue stress spectrums and the fatigue life of longitudinally connected ballastless track on bridge under combined loads is important to improve high-speed railway design level and perfects ballastless track design theory in our country. Based on Natural Science Foundation of China (51178469), the fatigue stress spectrums and the fatigue life prediction of longitudinally connected ballastless track on bridge under combined loads have been studied in this paper.The vehicle-longitudinally connected ballastless track coupling system model has been eatablished for achieving clamping force time-history of fasteners in this paper. The calculation model of temperature gradient based on heat transfer theory has been established in order to gain the temperature gradient time-history curve.The longitudinal interaction between steel bar and concrete mechanic model which considered concrete crack has been established for calculating the stress time-history of ballastless track under axial temperature and concrete shrinkage load.The stress time-history of ballastless track under temperature gradient and clamping force time-history of fasteners has been calculated respectively with the three-dimensional finite element space mechanical model of longitudinally connected ballastless track on bridge which considered concrete crack.Taking the stress time-history of ballastless track under clamping force time-history of fasteners, temperature gradient load, axial temperature and concrete shrinkage load into account, the fatigue stress spectrums of ballastless track under combined loads are calculated by rain-flow counting method.The fatigue life prediction model for longitudinally connected ballastless track on bridge under combined loads,which combines the S-N curves of steel bar and concrete,is established by means of Palmgren-Miner linear damage accumulation theory. The fatigue life and its influencing factors such as the thickness of plate, the reinforcement ratio, the crack spacing and the temperature of concrete construction of longitudinally connected ballastless track on bridge under combined loads are studied with established fatigue life prediction model.