Magnetorheological Damper For High-speed Train Through The Vibration Of A Simply Supported Box Girder Bridge Control Study

Among of the high-speed railway constructions of China, bridges are in a large proportion. Dynamic performances of train-bridge interaction system under the loads of high-speed trains and have been put on the agenda. The vibration problem of bridge as a kind of intelligent and active or semi-active strategy, basing on the teamwork of the control system and structure to withstand external power input, in order to decrease the dynamic response of train-bridge, and increase the safety and stability of travelling.As the development of smart materials in recent years, as a new type of damper, magneto rheological damper (MRD) attracts widespread attention. It can generate variable and real-time damping force by adjusting the magnetic filed strength. It is more reliable comparing with the traditional mechanical adjustable damper for it takes out the mechanic valve. The major work has been done as follows:Firstly,the working-principle and mechanical models of magneto rheological damper. Several classic mechanical models of MRD have been elaborated systemly, and adopted the amended phenomenon-mod- el which which can response the performance of the model correctly.Secondly, the train-bridge-MRD interaction system. After choose the model of MRD and simulating the model of the train vehicle on the bridge, the model with two bogies and four wheels, was established for vertical analysis. As the same time, 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 uniformed speeds and bridges with arbitrary surface roughness functions and different constraints.Thirdly, the solving and the analysis program of the train-bridge-MRD interaction system. An all-purpose program for vertical dynamic analysis of train-bridge-MRD interaction system and a program for the simulation of surface roughness were developed using FORTRAN 95. Using the dynamic analysis program of train-bridge-MRD interaction system, the dynamic properties analysis of train-bridge-MRD 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 uniformed speeds can be analyzed. Moreover it can take surface roughness and MRD into consideration.Fourthly, the solving of the opimal control force of MRD. First,the optimal control of structure under external loads is calculated by instantaneous optimal control, and the dual-threshold control algorithm of the semi-active control strategy of MR damper is built on the basis of the theory of active control, and then combined with the current state of damper; the damping force of model which will be used in the bridge to control structural vibration is calculated by control algorithm limits (semi-active control algorithm).Finally, the analysis of the vibration-reducing of the MRD to the bridge. This paper maded a new vibration-reducing model which was made of MRD and anchor. The effects of MRD were studied on vibration suppression of simply supported bridges and vehicles when high-speed trains were moving on the beam. A case study using 40-metre and 32-metre simply supported PC box beam bridges was conducted. The results show that the MRD has better effects on reducing the resonant responses of the bridge. Therefore it is suggested to apply into practice. Besides, the effect of MRD on smooth performance for railway vehicles was discussed. Through the analysis shows, MR dampers for vibration control of bridges are feasible.