Dynamic Interaction Analysis Of Wind-Linear Induction Motor Vehicle-Bridge System

As a new rail transit form,the linear induction motor(LIM)rail transit is introduced to China in recent years.It uses electromagnetic force as traction force,which makes the dynamic performance of the rail transit have its own characteristics.Due to the special monsoon climate in coastal areas,it cannot be ignored the influence of wind load on the operation of rail transit in this district.Currently,there is less research on dynamic interaction of LIM train-bridge system,especially in the field of wind-LIM train-bridge system,which takes the crosswind action into account.In order to guarantee the line operation safety,it is necessary to carry out the research on train-bridge vibration mechanism and train driving safety subjected to crosswind.Based on the existing research,it divides the train and bridge into two independent subsystems.Then on the basis of wind-train coupling dynamics,wind-bridge coupling dynamics and train-bridge coupling dynamics,it establishes a wind-LIM train-bridge interaction vibration spatial model in this dissertation,which can take the combined effect of wind-excitation,electromagnetic force,track irregularity and hunting wave excitation into comprehensive consideration.In addition,a computer program is developed.In general,the following aspects have been done in this dissertation:(1)In order to improve the simulation efficiency of random excitation in vibration system,the numerical simulation methods are studied.On one hand,a random process expansion method based on orthogonal basis is adopted for the track irregularity simulation in time domain,the simulation formula is deduced and the corresponding program is also developed.On the other hand,it improves simulation method of the fluctuating wind field,which is on the basis of the spectral representation method with proper orthogonal decomposition(POD),by introducing the double-indexing of the frequencies and FFT acceleration algorithms.And it succeeds to simulate the ergodic fluctuating wind field of long-span bridges,which considers the cross-spectral density as the target of POD.Numerical study shows that both of proposed methods improve the computational efficiency.(2)On the basis of D’Alembert principle,the Equation of Motion(EOM)of LIM train with 31 degrees of freedom under different suspension modes is derived.By considering the aerodynamic force of bridges and trains,and adopting the wheel-rail dynamic coupling model which can take track irregularity dynamic effects into account,it establishes an interaction vibration spatial model of wind-LIM train-bridge system.Then based upon iterative method in groups,and taking the displacement between train and bridge as constraint condition,an approach belonging to step by step integration method in time domain is adopted to solve the system dynamics equations.In addition,a Wind-vehicle-bridge Coupling Vibration Analysis Program(WVB)is developed and verified.(3)Taking a three-span 30 m simple supported box girder viaduct of Guangzhou Metro Line 4 as background,a wind-LIM train-multiple spans simple supported girder bridge system vibration model is established to analyze system vibration response,which takes consideration of various factors such as track irregularity,wind velocity,train velocity,electromagnetic force mode,magnetic pole air gap and so on.The results show the following aspects: firstly,the track irregularity dynamic effect increases the vibration response of train and bridge,especially in acceleration response of bridge and safety coefficient of train.Secondly,wind velocity is the key determinant factor to system operation safety.The dynamic effect of crosswind is week to the bridge with large stiffness and high natural frequency,so the system operation safety is controlled by the train.Thirdly,the frequency of excitation force of train on bridge is changed with train velocity variation.And resonance phenomenon comes out when the frequency is close to the natural frequency of bridge.Fourthly,little influence on train and bridge dynamic response is due to magnetic air gap variation.Furthermore,by using electromagnetic attraction mode,it increases the vertical pressure of wheel to reduce wheel load reduction rate and the train derailment coefficient,which is conducive to rail operation safety.(4)Taking Ronggui Shuidao bridge with a 185 m main span as background,which is on the route of Guangzhou-Zhuhai light rail,a wind-LIM train-long span continuous rigid frame bridge system vibration model is established to analyse system vibration response,which takes consideration of various factors such as track irregularity,wind velocity,train velocity,electromagnetic force mode,magnetic pole air gap and so on.The results show the following aspects: firstly,with the increase of train velocity,the track irregularity dynamic effect on vibration response of system increases.Secondly,wind velocity is the key factor of system horizontal dynamic response.The dynamic effect of crosswind is week to the bridge,however,the static displacement of the bridge increases with increase of wind speed.And the system operation safety is controlled by train.Thirdly,the system dynamic response increases with the increase of train velocity,and when the wind velocity of fluctuating wind field is constant,train speed should be limited to guarantee the traffic safety.(5)Taking the Baisha River bridge with a 150 m main span as background,which is on the route of Guangzhou Metro Line 6,it establishes a wind-LIM train-long span combined arch bridge system dynamic model to do system vibration response analysis,which takes wind speed,train speed,train load and other factors into consideration.It deduces the simplified analytical formula of critical wind speed,and ultimately adopts the accurate analysis of time history to calculate critical wind speed of Baisha River bridge.The results show the following aspects: firstly,the bridge is sensitive to wind load,and the horizontal dynamic response of train and bridge increases significantly with the increase of wind speed,which is greater than 20m/s.Secondly,the system response affected by train speed variation varies greatly with different wind speeds.Thirdly,both the derailment coefficient and wheel deduction rate of running empty are a little larger,which is dangerous to be avoided in strong wind.Fourthly,because of all-around consideration of various affecting factors,the result of critical wind speed,based on the accurate analysis of time history,is more accurate.