Study On Seismic Response Of Train-bridge Coupling System And Earthquake Alarm Threshold

With the rapid development of high-speed railway, high-speed rail has become an important part of the main artery of national economy and force of transportation industry. Transport safety has been put in an important position in the “12th five-year plan” in which the target “developing large-capacity, safe and comfortable, all-day working and high-speed railway” was put forward. As earthquake occurs frequently in our country, it has seriously threatened the high-speed rail network throughout the country. Meanwhile, bridges have covered more than 50 percent of the railroad line by far, it is of great probability that the high-speed train running on the bridge when an earthquake occurs, research on seismic security evaluation and seimic alarm threshold that considering train-bridge coupling effect need to be promoted.Researches on earthquake alarm and emergency disposal system in our country have just started, and not yet been tested by real earthquakes, experience accumulated is limited. Rationality of technical parameters such as alarm threshold etc. needs to be demonstrated. The key problems should be solved include:(1) construction of reasonable train-bridge coupling system;(2) earthquake response analysis of train-bridge coupling system;(3) seismic safety evaluation of high-speed train based on Chinese high speed railway track spectrum;(4) confirmation of resonable seismic alarm threshold for high-speed train.Researches are carried out for these key problems, the main content and research findings of the paper are as follows:1. Model research: Specific parameters for numerical simulation are confirmed,including parameters of train, bridge model and contact relation of the train-bridge coupling system. In order to obtain the acceleration response of the bridge deck,Connections between bridge and train are built by springs ascertained by Hertz nonlinear theory and tangential contact relationship, a reasonable high-speed train and bridge coupling model is set up, the train is simulated by 6 degrees equivalent rigid body model. Meanwhile, a bridge model with equal spans not considering high-speed train is also set up for comparison. Necessity of the model is also verified by dynamic characteristic analysis. In order to evaluate the seismic safety and acquire the earthquake alarming threshold of the high-speed train, based on the parameters of the high-speed passenger locomotive, a train-track coupling model with 31 degrees is established. The train is modeled consisting of a body, two trucks and four wheel sets.The body and each truck are considered to have 5 DOFs of transverse and vertical displacements, rolling, pitching and yawing respectively. The wheel set is considered four 4 DOFs of transverse and vertical displacements, rolling and yawing.2. Earthquake response analysis of train-bridge coupling system: Typical earthquake acceleration records are selected as intrinsic motivation, earthquake response analysis of train-bridge coupling system are carried out to get the deck acceleration and amplification factors. Effects of earthquake frequency spectrum characteristics on the seismic response of the bridge deck are studied. Meanwhile, through the seismic response comparison between train-bridge coupling model and single bridge model,the response diversity of these two model is acquired which futher verifies the necessity of the train-bridge coupling model. In addition, seismic response of the train-bridge coupling system with different pier type and height are calculated to analyse the influence on seismic response. Vertical displacement of the beam and lateral displacement of the pier are also checked according to the code requirement.3. Seismic response analysis of high-speed train: Taking the deck acceleration time history of the train-bridge coupling system as input excitation, chosing Chinese and Germany track irregularity as the internal motivation separately, based on train-track coupling dynamics theory, Earthquake response analysis of high-speed train is carried out, Three indicators for train safety evaluation include derailment coefficient,reduction rate of wheel load and wheel rail lateral force are finally obtained by Hertz nonlinear theory, Kalker linear theory, Hedrick-Elkinss theory and space relationship of the wheel and track. Comparing with the limit of the three values in the code, the running safety of the high-speed train is estimated. The results comparison between Chinese and Germany track irregularity shows that, three indicators obtained by Germany track irregularity is larger and danger than Chinese irregularity.4. Research on seimic alarm threshold of high-speed train: selecting typical earthquake records with different spectral characteristics, by adjusting the peak value of the earthquake records with a great quantity of calculation and analysis, limit value curve under different intensity of ground motions at the different train speed will be obtained, envelope values corresponding to the curve will be get and simplified.Finally, suggested earthquake emergency disposal threshold and simplified formula will be put forward. Comparing with Germany track irregularity, earthquake alarm threshold obtained by Chinese track irregularity is much lower.