High-speed Trains Through The Bridge When The Variable Speed Effects And Vibration Control Study

As the significant increase of Chinese comprehensive strength, highspeed railway constructions could have the opportunity to develop rapidly. Among of the constructions, bridges are in a large proportion, especially the simply supported box beams and continuous box beams. Dynamic performances of train-bridge interaction system under the loads of highspeed trains and the riding comfort of trains have become important and urgent problems. Considering the two conditions of a vehicle with variable speeds and vibration suppression using tuned mass dampers (TMD), some elementary researches were done in this thesis on the train-bridge interaction system. A time domain analytical approach of vibration of train-bridge system, in which the effects of variable speeds and TMD could be considered, was presented. Correlative programs were developed and the responses of the trains and the bridges of simply supported box beams and continuous box beams were analyzed under moving highspeed trains. The major work has been done as follows:Firstly, analysis model of the train vehicle with two bogies and four wheels, was established for vertical analysis. The finite element model of the bridge and the surface roughness model were also built. Then based on the virtual work principle, the dynamical equations of the coupled train-bridge system were deduced. The equations are applicable to the system composed by vehicles with variable speeds and bridges with arbitrary surface roughness functions and different constraints.Secondly, the system of TMD was simulated on the base of the vibration suppression principle of TMD system. The dynamical equations of the train-bridge interaction system were expanded to the dynamical equations of the train-bridge-TMD interaction system.Thirdly, an all-purpose program for vertical dynamic analysis of train-bridge-TMD interaction system and a program for the simulation of surface roughness were developed using FORTRAN 90. And a program for calculating the index of evaluating smooth performance of railway vehicles was developed using Matlab. Using the dynamic analysis program of train-bridge-TMD interaction system, both the static analysis and dynamic properties analysis of bridges and the vertical dynamic analysis of train-bridge-TMD interaction system can be done. It is applicable to the bridge models which can be simulated by beam, truss and cable elements, and moving load and the vehicle models which can be predigested into mass-spring-damper systems. The responses of train-bridge interaction system under high-speed trains with uniformly variable speeds can be analyzed. Moreover it can take surface roughness and TMD into consideration.Fourthly, the dynamic responses of vehicles and bridges were studied while the high-speed trains with uniformly variable speeds were traveling on simply supported box beams and continuous box beams. The effects of vehicle shifting position, initial velocity and acceleration or deceleration were discussed. Influence coefficient was introduced to scale the difference of dynamic responses of bridges between under trains in uniformly variable speeds and under trains in a constant speed. The results show that the effects of initial velocity, acceleration or deceleration and vehicle shifting position should be considered comprehensively to analyze the influence on dynamic responses of bridges due to trains with variable speeds. It is also found that the peak value of vehicle body acceleration responses usually increases in accelerated motion, while it decreases in decelerated motion compared with that in uniform motion.Fifthly, the approximate formula for calculating the critical speeds was validated. The impacts on resonant responses of the bridge caused by bridge span, loaded frequency and surface roughness were discussed.Sixthly, the effects of TMD were studied on vibration suppression of simply supported bridges and vehicles when high-speed trains were moving on the beam. A case study using a 40-metre simply supported PC box beam bridge was conducted. The parameters of TMD were determined by Den Hartog's optimal criterion and the minimum-maximum approach separately. The results show that the method to determine the parameters of TMD by Den Hartog's optimal criterion is simple and has better effects on reducing the resonant responses of the bridge. Therefore it is suggested to apply into practice. Besides,the effect of TMD on smooth performance for railway vehicles was discussed.Finally, vibration suppression analysis for continuous bridges and vehicles using TMD under high-speed trains was further done.