Study On Semi-active Parametric Vibration Control Of Cables And Optimized Placement Of MR Damper For Cable-stayed Bridges

As main supporting components of cable-stayed bridges, cables with small mass, low damping and large flexibility are easy to induce large amplitude vibration in wind, rain and excitation vibration of deck and other external excitations etc., such as vortex-excited resonance, wake galloping, parametric resonance and rain-wind induced vibration. On one hand, large amplitude vibration can cause fatigue failure of cables which threats service life of cables and safe operation of a bridge; on the other hand, large amplitude vibration induces the suspicion of the safety of a bridge. Therefore, the accurate analysis of cable vibration mechanism and characteristics, especially for cable parameter vibration with amplitude of several meters, has important academic significance and engineering application value to seek the effective vibration control measures.Taking the Guizhou Hongshuihe hybrid girder supermajor cable-stayed bridge with213+508+185meters spans in design stage as the engineering background, the issues of semi-active parameter vibration control of cables based on MR damper (MRD) and the optimized placement of MRD are investigated deeply. The main research contents and results are summarized as follows:1. The present MRD dynamic models were summarized. Based on the experimental data of the RD-1097MRD and analysis, a new dynamic model, nonlinear Bingham hysteresis model, which can not only reflect the hysteretic characteristics between the damper and velocity of MRD physically, but also can better reflect the new mechanical model in low speed, was proposed. The new model in the ANSYS numeric analysis was studied and the simulation of nonlinear Bingham hysteresis model was realized by using COMBIN37element in the finite element software ANSYS.2. The natural vibration characteristics of the stay cables including sag effect and the non-linear parameter vibration characteristics of the stay cables under the end axial periodic excitation were analyzed through theoretical calculation and numerical simulation by ANSYS. Transient dynamic analysis was carried out on the vibration of the stay cables under the end axial periodic excitation by ANSYS, and results of ANSYS analysis were compared with those theoretical results, which laid a foundation for study on the primary resonance and the parameter resonance control of the stay cables under the end axial periodic excitation.3. The study on the passive control of cable-MRD system under the primary and parameter resonance induced by the end axial periodic excitation was carried out by ANSYS software. The APDL programs of vibration control of cable-MRD system were compiled. Meanwhile, the effects on vibration control with primary and parametric resonance of stay cables at different conditions, including passive-off (OV) and Passive-on (2.5V), excitation amplitudes, the installation position and the installation angles, were investigated.4. Based on fuzzy logic theory, a fuzzy semi-active control strategy of vibration control of cable-MRD system under primary and parametric resonance was proposed. The APDL fuzzy semi-active control programs of cable-MR damper system were compiled. The effects of fuzzy semi-active control were compared with the effects of passive control. The control effect of the proposed fuzzy semi-active control strategy was better than that of passive control. The fuzzy control strategy presented in this paper which adopted the fuzzy controller to control input voltage of MRD was simple and practical.5. Based on the fuzzy semi-active control strategy, the improved fuzzy semi-active control strategy was proposed. By introducing the quantitative factor fuzzy controller, the quantitative factor can be adjusted adaptively according to the different cable vibration conditions. The process of the fuzzy semi-active control through a large number of attempts to determine the basic domain of input, output variables and quantification factor corresponding was greatly simplified. In comparison with the fuzzy semi-active control strategy, the effect of the improved strategy was slightly better than that of the fuzzy semi-active control strategy. In addition, the improved strategy was more convenient and intelligent and had a high control efficiency. 6. Study on the optimized placement of MRD in vibration control of cable parametric resonance under eight different working conditions was carried out. The optimized placement method of MRD in cable-MRD system was proposed. To establish a multi-objective function, the optimized placement of MRD was programmed based on MATLAB and ANSYS, and the optimized calculation was complishied by the genetic algorithm. The result showed that the presented method of MRD optimized placement was feasible and effective.The research results will provide basis for the cable vibration suppression of the Guizhou Hongshuihe hybrid girder supermajor cable-stayed bridge.