| As China’s high-speed railway construction extends from land to sea,cross-sea bridges have become an important part of high-speed railway lines.Compared with ordinary bridges,cross-sea bridges face deep water environments and are subject to long-term wave forces.Once an earthquake occurs,additional hydrodynamic pressure will be generated in the lower structure of the bridge.As China is located between the Pacific and Eurasian seismic belts,with high frequency,intensity and wide distribution of earthquakes,the probability of highspeed railway cross-sea bridges being subjected to wave forces,earthquake forces and additional hydrodynamic pressure from earthquakes at the same time is very high.The safety of train operation needs to consider the combined effect of waves and earthquakes.This paper takes the cable-stayed bridge,which is most commonly used in high-speed railway cross-sea bridges,as an example and focuses on the safety of train operation under the combined effect of waves and earthquakes.The main work and results are as follows:(1)Based on linear wave theory and Morsion equation,a numerical simulation module for wave load was established.The additional mass method was used to simulate the additional hydrodynamic pressure from earthquakes.A train-track-bridge coupled vibration model under the combined effect of waves and earthquakes was established based on TTBSAS and its accuracy was verified.The results show that: the numerical simulation values of waves fit well with the experimental values in literature;the train-track-bridge coupling model is accurate and effective.(2)The influence of waves on the coupled vibration of train-track-bridge system in highspeed railway cross-sea bridge was studied.The distributed force mode was used to input wave load into existing train-track-bridge coupled vibration analysis program.Taking a highspeed railway cross-sea cable-stayed bridge as an example,the effects of wave slope surface effect and wave recurrence period on dynamic response of train-track-bridge system were studied.The running performance of vehicles crossing bridge under common(10-year return period)and extreme(100-year return period)waves were evaluated.The results show that: for this calculation example,when the lateral reference coordinate for inputting wave force is located on both sides of pile group,dynamic response of coupling system is greater than when reference coordinate is located at center of pile group.With increase in wave recurrence period,lateral dynamic response of vehicle-bridge system increases while vertical dynamic response remains almost unchanged.Wave load significantly reduces ride comfort of trains on bridge and increases derailment risk;without considering wave load all calculated speeds(250～350km/h)are safe for vehicles crossing bridge while safe speed thresholds for trains under common and extreme waves are only 325km/h and 275km/h respectively.(3)The coupled vehicle-bridge vibration problem of a sea-crossing cable-stayed bridge under the combined wave-earthquake effect is systematically studied.Taking a 400 m main span cable-stayed bridge as an example,several sets of working conditions were set up according to the wave parameters and ground vibration parameters at the bridge site,and several key issues were discussed.The results show that the seismic response of the cablestayed bridge in the cross-bridge upward direction is significantly increased by the ground vibration hydraulic force,and ignoring the ground vibration hydraulic force will lead to small calculation results of the dynamic response of the bridge,track and train.The combined waveearthquake effect on the coupled train-track-bridge system,seismic waves are the main source of excitation causing bridge vibration,and the sensitivity of the track and train subsystems to external loads increases with the increase of vehicle speed.There is a significant difference in the amplitude of the dynamic response index of the train on the bridge under different combinations of seismic waves and waves,and the calculation results of multiple seismic waves need to be considered for comprehensive assessment.The wave return period and vehicle speed both affect the dynamic response of the vehicle-rail-bridge system,and need to be considered for the study of driving safety under the combined effect.(4)The driving safety when trains crossing bridge under combined action wavesearthquakes was studied traditional indicators new derailment evaluation indicators were compared analyzed.Average values for train dynamic responses under multiple earthquakewave-wave combinations were taken to evaluate driving safety when trains crossing bridge new derailment evaluation criteria were used determine safe speed threshold when trains crossing bridge.Results show that: comprehensive evaluation using multiple standards can effectively avoid misjudgment driving safety.When earthquake intensity is constant speed another important factor affecting driving safety except external load;comprehensive index safe speed threshold 10a～100a-multi-earthquake combination action 250km/h. |
