| In order to meet the requirements of functional diversity,appearance aesthetics and urban planning of modern structures,the building structures often presents asymmetric plane layout and irregular facade layout,resulting in complex spatial torsion vibrations under the action of earthquakes.Spatial torsional vibrations will even become the main factor leading to building collapse in some cases.Therefore,it is necessary to study and control the structural torsional vibrations due to seismic excitations.As a typical representative of semi-active control technology,the magnetorheological(MR)damping technology combines the effectiveness of active control and the reliability of passive control,and provides a new idea for the control of structural seismic response.The effectiveness of MR damping technology in structural torsional vibration control has also been preliminarily verified theoretically and experimentally.However,MR intelligent damping technology is an interdisciplinary subject.There are still many unresolved problems in the magnetic field characteristics,mechanical properties and mathematical models of MR dampers,and its application in the field of spatial torsional vibration control of complex structures is not enough.Therefore,aiming at the key problems of MR intelligent damping technology and its application in structural spatial torsional vibration control,combined with experimental research,theoretical analysis and numerical simulation,this study systematically studies the magnetic field distribution and mechanical properties of MR dampers,dynamic analysis and torsional vibration control of MR damped structures,cooperative control algorithm and optimization design of MR control systems.The main contents of the present work are listed as follows:(1)Internal magnetic field tests and analysis for multi-coil MR damperFirstly,a three-coil MR damper with a built-in hall sensor is fabricated based on magnetic circuit analysis and structure design,and the measured data of internal magnetic induction intensities under different excitation currents and electrify conditions are obtained.Then,the simulation value of the internal magnetic induction distribution of the three-coil MR damper is obtained by finite element analysis,and compared with the internal magnetic field test data to verify the accuracy of the magnetic field finite element analysis.Finally,using the finite element analysis data,the magnetic field coupling of the three coil MR damper under different excitation currents and electrify conditions is analyzed,and a magnetic field coupling model describing the internal magnetic field coupling effect of multi-coil MR dampers is proposed.(2)Mechanical performance tests of multi-coil MR damperFirstly,the mechanical properties of MR damper with different volume fraction of trapped air are tested,and the effects of internal air volume and excitation properties on the ‘force hysteresis’ phenomenon of MR damper are analyzed.Then,the constant current test of the three coil MR damper is carried out,and the mechanical properties of the MR damper under different power on condition combinations and different excitation properties are mainly analyzed,and then the energy dissipation capacity and hysteretic characteristics of the MR damper under different working conditions are compared.Finally,using the developed MR integrated intelligent control system,the excitation current varying with the displacement amplitude is applied to the MR damper,the mechanical properties of the MR damper under time-varying current are studied,and the influence of ‘magnetic hysteresis’ phenomenon on the mechanical properties of the MR damper is analyzed.(3)A multi-factor mathematical model of MR dampersFirstly,based on the magnetic field coupling model,combining the modified micromechanical model of MR fluid considering the uneven distribution of magnetic particles and mechanical property test data,a refined mathematical model is proposed,which can comprehensively consider the influencing factors such as micro parameters of MR fluid,damper dimensions,control current,excitation properties and magnetic saturation effect.Then,the effectiveness and accuracy of the proposed model is verified by comparisons with performance test results.Finally,based on the proposed multi-factor refined mathematical model,the influence of micro parameters of MR fluid on the macro mechanical properties of MR damper is analyzed.(4)Cooperative control of the MR damped structure considering the spatial torsional vibrationFirstly,based on the spatial member model,a 10-story complex spatial eccentric structure model considering plane asymmetry and facade irregularity is established in OPENSEES.Using the function of self-defined materials in OPENSEES,the nonlinear dynamic properties of MR damper are introduced to the structure model.Then,the elastic-plastic time history analysis of the uncontrolled structure and the structure with MR dampers under earthquake is carried out,and the torsional vibration characteristics of spatial eccentric structures and the control effect of MR dampers on torsional vibrations is analyzed.Finally,based on the ant colony algorithm that considers the interaction between different MR dampers through ant path selection and information update,a control algorithm for cooperative control of multiple MR dampers is proposed.The effectiveness and superiority of the cooperative control strategy is verified by comparing the seismic responses of the MR damped structure model with different control strategies.(5)Comprehensive optimization analysis of the MR damped structure considering the spatial torsional vibrationFirstly,considering the control of translational vibration and torsional vibration of the structure at the same time,using the multi-factor refined mathematical model proposed in this paper and the elastic-plastic time history analysis program of MR damped structures,a comprehensive optimization analysis method based on genetic algorithm for the micro-structure parameters of MR fluid,the size,installation position and number of MR dampers in the control system with multiple MR dampers is proposed.Then,the control effect of the MR control system on the structural vibration response before and after optimization is compared,and the feasibility of the comprehensive optimization design method proposed in this paper is verified.The main innovations of the present work are listed below:(1)By introducing a coupling coefficient to consider the coupling effect of magnetic field generated by adjacent coils,a magnetic field coupling model which can accurately describe the internal magnetic field distribution of multi-coil MR dampers is proposed.Combining the magnetic field coupling model with the modified micro-model of MR fluid,a mechanical model considering the micro parameters of MR fluid,excitation properties and magnetic saturation effect is proposed.(2)The path selection and information exchange behavior of ants in the ant colony algorithm are used to simulate the interaction and synergy between different MR dampers,and a cooperative control strategy of many MR dampers in the MR control system is proposed.(3)Taking the cooperative control of translational and torsional vibrations of torsional irregular structure as the optimization goal,the microstructure parameters of MR fluid,the size,installation position and number of MR dampers are optimized based on the genetic algorithm,and a comprehensive optimization design method of MR damping structure is constructed. |
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