Optimal Design Of Shock Absorption Of Eddy Current Tuned Mass Damper Based On Endurance Time Method

Tuned mass damper is a passive control device with the advantages of simple structure,good economy,stability and reliability.It is widely used in practical engineering.Eddy current damper has significant advantages as a damping element of TMD because of its friction free,simple structure and easy adjustment of damping coefficient.The eddy current damping element of planetype eddy current TMD has the advantages of no friction and high reliability,but there is a problem that the energy consumption density of eddy current damping element(the ratio of damping force to weight of damping element)is slightly small.The control effect of TMD is closely related to its own parameters.Scholars at home and abroad have put forward many parameter optimization methods of TMD according to the load characteristics and structural dynamic response characteristics of vibration reduction control;Among many optimization methods,especially the TMD which controls the seismic action is the most difficult,and the damping coefficient of TMD are highly required.The endurance time method has the characteristics of high calculation efficiency and less analysis times.It can quickly and accurately evaluate the seismic performance of structures.In this paper,the endurance time method is used to optimize the parameters of structures equipped with TMD based on Non-dominated sorting genetic algorithm-Ⅱ(NSGA-Ⅱ).It is expected to obtain a new method to optimize the shock absorption parameters of TMD.The main work and achievements are as follows:(1)This paper introduces the working principle of the plane-type eddy current damper with two pairs of permanent magnets,makes a dimensionless analysis on the influence of its parameters on the damping coefficient,summarizes the design method of the plane-type eddy current damper with two pairs of permanent magnets to obtain a larger damping coefficient,and proves through an example that the design method can effectively save the conductor plate material,and on this basis,the damping coefficient is increased by 34.3%.The damping force velocity characteristics of eddy current damper are discussed.It is found that the increase of conductor plate material conductivity and conductor plate thickness can improve the damping coefficient,and the damping force velocity nonlinearity of the damper will be enhanced.(2)Based on the principle of equal dissipated energy,the formula of nonlinear damping equivalent to linear damping ratio of plate eddy current TMD is deduced.The accuracy of the formula of equivalent linear damping ratio is verified by the dynamic equation of the system.Under the same damping ratio,the shock absorption control effects of eddy current TMD and linear viscous TMD on the structure are compared.Generally speaking,the shock absorption control effects of eddy current TMD and linear viscous TMD are not different.The peak value of additional damping force provided by eddy current TMD is less than that provided by linear viscous TMD.The shock absorption control effect of the structure is compared between the eddy current TMD with the optimal parameters obtained by genetic algorithm and the linear viscous TMD with the optimal parameters obtained by closed formula.The results show that the shock absorption control effect of the eddy current TMD is generally better than the linear viscous TMD.(3)The principle of endurance time method and the generation method of endurance time accelerogram curve are introduced in detail.The seismic performance of six-story reinforced concrete frame and ten-story steel structure frame are analyzed by using OpenSEES platform.The endurance time accelerogram curve directly affects the accuracy of the results of the endurance time method.The analysis results of IDA method and endurance time method are compared.The results show that the endurance time method can accurately evaluate the maximum displacement of the top and the maximum shear force of the base of the frame structure.When evaluating the maximum story drift ratio of the structure,there is a little deviation between the analysis result of endurance time method and that of IDA method.After adjusting the target spectrum of endurance time accelerogram curve,the mean value of endurance time method is in good agreement with that of IDA method.(4)An optimization design method of TMD parameters based on NSGA-Ⅱis proposed.The effectiveness and robustness of the optimized parameters are verified.Under different types of seismic input,TMD has good shock absorption control effect on the structure,and the control effect of TMD also has good robustness in the case of structural parameter deviation.Compared with other TMD shock absorption parameter optimization methods,the control effect of TMD obtained by this paper method is close to that of other methods,and the damping coefficient of TMD proposed in this paper is small,which shows that the TMD designed by this method has good shock absorption control effect and robustness.The optimized parameters of the damper in the eddy current TMD are obtained by using the optimized linear viscous TMD damping ratio.The control effects of the optimized eddy current TMD and linear viscous TMD on the structure under three groups of different seismic loads are compared.From the average control effect,the damping control effect of eddy current TMD on the structure is better than that of linear viscous TMD.