Vehicle-bridge Coupling Vibration And MTMD Vibration Control Of A Cable-stayed Bridge

Nowadays the bridge structures are always under a busy transportation condition for the development of traffic and logistics. The traffic density, the load and moving speed increase day by day, which attract much attention on the interaction of the vehicles and bridges. On one hand, the dynamic characteristics of the moving vehicle influence the working condition and the age of structure directly. On the other hand, the comfortable and safe requirement is a critical factor for evaluating whether or not the structural dynamic parameters are chosen suitably in the design. Therefore, discussion on the dynamic coupling system of vehicles and bridge, analysis on the dynamic performances of the structure and the balanced moving performance of the vehicles, and the research on the countermeasure to minimize the dynamic response are an available demand for the rational design of the large-span bridges, which will contribute deeply to the theoretical and practical improvement of structural engineering field. Supported by the Program for New Century Excellent Talents in University (2004), an actual cable-stayed bridge named Tie-luo-ping bridge in the west part of Shanghai-Chengdu national highway is chosen as a case study in this thesis. The study focuses on the dynamic interaction of vehicle-bridge system and the dynamic responses of the bridge under MTMD control, which will provide mechanical reference to the rational design.The bridge is a long span concrete cable-stayed structure of high-pier with double towers and double cable planes. Firstly, the static analysis is carried out using the finite element method, and reasonable original stress condition of the bridge is established by regulating original cable stress, afterwards, the dynamic characteristics are discussed. Secondly, the vehicle on the bridge is simulated as a vibration system with two axes, six freedom and three masses, and the vehicle's dynamic characteristics are studied. The coupling system including the vibration of vehicles and bridge structure is set up based on the vehicle-bridge coupling element due to pavement's stochastic irregulation, the motion equation is solved by numerical integration method. Attention has been paid on the relationship among the bridge's dynamic response, passengers'comfort degree with the moving vehicle under different speeds, vehicle number and eccentric loading. Thirdly, based on the analysis of Tie-luo-ping bridge's natural vibration, the structure's control modal of dynamic deflection in mid-span is acquired. The vehicle load is considered as the stochastic excitation. The dynamic equation of the new system which is constituted with control modal coordinate of structural vibration and MTMD is founded, from which the amplitude frequency response equation is deduced. The relationship between the average damp ratio, frequency space, generalized mass, quantity, layout space with coordinate amplitude of control modal is analyzed, and the process of how to determine the various MTMD parameters is offered in details. The MTMD is designed to aim at controlling the dynamic deflection of mid-span, and the dynamic response of vehicle-bridge system is studied under the control of MTMD. The numerical results show that, for the stochastic irregular pavement, MTMD can effectively minimize the structure's dynamic response under vehicle load excitation.Finally, the future research on the vehicle-bridge coupling interaction and its control is discussed. It will be prosperous in the economic and societal efficiency. Consequentially, with the endeavor of researchers, the application of vehicle-bridge dynamic interaction theoretical achievements will be more effective in practical engineering design, and the structural control technology will play a more important role in structure's protecting against vibration and mitigating disaster fields.