| The high-speed railway has developed rapidly around the world in the last decade,especially in China,due to its advantages such as fast operating speed and comfortable performance.China has a vast territory and different climates in different parts of the country.With the increase of train running speed and the reducing weight,the complicated wind environment makes the safety issue of trains more prominent.Under strong crosswind,the aerodynamic force acting on moving vehicle can increase the rolling moment around leeward rail thus increase the overturning risk.The paper focuses on the aerodynamic characteristics of moving trains under crosswinds.By establishing the analytical models of wind turbulence and coherence function relative to moving vehicle,a simplified frequency framework for assessing the overturning risk of train running under crosswind is derived.The overturning risk of train running on the bridge structure is furtherly discussed.Include following major respects:(1)Based on the developed moving train wind tunnel test system,the system layout,test stability and system applicability are described and evaluated in detail.The aerodynamic forces test was carried out to analyze the difference of aerodynamic coefficient between moving and static train models,and the influence of Reynolds number,wind speed,wind direction angle,vehicle speed and the shadowing effect of bridge on the aerodynamic coefficient.Numerical simulation is also conducted to figure out the influence of interenode effect and infrastructures on the aerodynamic characteristics of moving trains.(2)A closed-form expression for the wind turbulence relative to moving train is developed.Based on the Taylor frozen assumption,the wind turbulence relative to a moving train is established by using wind turbulence spectrum fixed on the ground and coherence function,which is proved to be suitable for any kinds of wind turbulence spectrum fixed on the ground and coherence function.The closed-form expressions for the wind turbulence and coherence function relative to a moving train is then proposed by the help of dimensionless analysis.(3)A closed-from framework in frequency domain for calculating the dynamic response and overturning risk of high-speed trains under strong crosswind is developed.The frequency domain analysis results show that the overturning risk of high-speed train is mostly dominated by two low-frequency modes,thus a furtherly simplified train model is introduced.Combined with the modal analysis,closed-form expression for the wind turbulence and extreme value distribution,the frequency analysis framework used to assess the overturning risk of highspeed trains can be calculated in a closed-form way with considering the risk probability.(4)Based on multi-body dynamic and mode superposition method,a train-bridge coupled system is established to assess the overturning probability of vehicle running on the bridge.The time domain analysis compares the influences of track irregularities,wind load and bridge vibration on the assessment of overturning risk.Meanwhile,the effect laws of bridge frequency and running speed on the coupling and resonance response of the train-multi-spans bridge system are revealed by a parameter analysis,and the occurrence condition and time effect for resonance effect are confirmed.A related simplified framework is introduced to deal with the overturning risk assessment of trian running on multi-spans bridge.(5)Based on the proposed frequency domain framework,the effect law of each calculated parameter on the overturning risk is revealed.The parameter uncertainties are introduced into the framework to figure out how these uncertainties will affect the trains' response,the overturning failure probability and characteristic wind speed curve.The biased estimate of the Lognormal distribution is adopted to give the confidence interval.The overturning failure probability for the train runs through the railway is estimated. |
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