Vibration Mitigation Performance Of Rotational Inertial Double Tuned Mass Damper For High-rise Structures

With the rapid economic development,a large number of towering buildings have been constructed all over the world.These towering structures have low damping and long period dynamic characteristics.Under the excitation of wind load and seismic action,excessive deformation is very easy to occur.This affects the comfort of the towering structures and threatens the structural safety.Therefore,the safety of towering structures under seismic action as well as the comfort and safety under wind load excitation need to be solved urgently.Tuned mass dampers(TMD)are characterized by simple construction,easy installation,stable performance and relatively low cost.It is a common method for energy dissipation and vibration reduction of towering structures.However,with the deepening of the application of tuned mass damper in towering structures,some special problems have been encountered.In order to solve the problems encountered by traditional TMD in towering structures,the following work is mainly done in this paper:The design of passively tuned damping devices for tall structures requires consideration of both the damping effect on the control target and the economics of passively tuned damping.The upper part of the towering structure has limited space,and the supported TMD control system requires less space for installation and use than the pendulum type and other passive tuning damping devices.Therefore,supported TMDs are often used for vibration control of tall structures.As the height of the building gets higher and higher,the bending deformation of the building becomes more and more obvious,and the floor rotation angle generated by the bending deformation of the structure will cause the tuned mass block to generate gravity component,which will change the control parameters of the TMD,thus affecting the vibration damping effect of the braced TMD control system and threatening the safety of the braced TMD control system.In order to quantitatively analyze the degree of influence of the floor rotation angle on the supported TMD control system,this paper establishes the tandem multi-degree-of-freedom equation of motion considering the floor rotation angle.Compared with the equation of motion of the tandem multi-degree-of-freedom system without considering the floor rotation angle,the tandem multi-degree-of-freedom equation considering the floor rotation angle has one more term of the inclination coefficient of the formation,which needs to be obtained by actual measurement or finite element model.For this reason,this paper establishes a threedimensional finite element model of a towering structure ETABS,obtains its formation inclination coefficient through modal analysis,and simplifies the three-dimensional finite element model of ETABS to a tandem multi-degree-of-freedom model under the premise of guaranteeing that the dynamic characteristics of the structure remain unchanged.The formation tilt coefficient represents the influence of the floor rotation angle,and the equations of motion with and without the formation tilt coefficient are solved through MATLAB programming,and the results are compared and analyzed in order to investigate the influence of the floor rotation angle on the supported TMD control system.Design tests to verify the influence of floor rotation angle on the supported TMD control system.The damping effect of passively tuned damping devices(TMDs)for towering structures is closely related to the size of the tuned mass ratio.Due to the limited space available in the upper part of a towering structure,it is difficult to install and operate large mass TMDs,which restricts the damping effect of TMDs,and there is an urgent need to develop higher performance passive tuned vibration damping devices to control the vibration of towering structures.The rotating inertia doubly tuned mass damper(RIDTMD)has been shown to be a passively tuned vibration damping device with higher performance compared to TMD control devices.However,the RIDTMD control parameters are more numerous,and studies on the optimal parameters of the RIDTMD are extremely limited in the literature.For this reason,a detailed study is done in this paper for obtaining the optimal parameters of RIDTMD.The optimal parameters of the three RIDTMDs based on the criterion are solved by following the parameter optimization process of the TMDs based on the criterion under wind load excitation and seismic action.Firstly,the equations of motion of the three multi-degreeof-freedom RIDTMD control systems under wind load excitation and seismic action are established,and the transfer functions of their control objectives are obtained by normalization and Raschner transformation.Secondly,the parameter theorem is used to solve the root mean square value of the control objective response.Then,the partial derivatives of the control parameters are obtained separately by using the root mean square value of the control objective to obtain the optimal parameter equation system.Finally,the three RIDTMD optimal control parameters are obtained by solving the system of optimal parameter equations.Since the optimal parameter equation system is a multivariate system of higher order equations,it is extremely difficult to obtain its analytical solution.Therefore,this paper proposes to take the root-mean-square value of the control objective as the objective function,and use the GA-NLP intelligent joint algorithm to obtain the numerical solutions of the optimal parameters of RIDTMD,and to prove the validity and accuracy of the obtained optimal parameters through the time-domain and frequency-domain analyses.Since GA-NLP is a kind of intelligent algorithm based on random search,in some cases the optimal parameters cannot be obtained or the optimal parameters will undergo a stepwise jump.To address this situation,this paper proposes to use BP neural network to nonlinearly fit the obtained optimal parameters,and then predict the optimal parameters of RIDTMD in special cases by BP neural network.In other words,the powerful nonlinear fitting ability of BP neural network is used as a supplement to GA-NLP to obtain the optimal parameters.The robustness analysis proves that the optimal parameters obtained by the joint algorithm of BP neural network and GA-NLP have strong robust performance.The main reason for the influence of the floor inclination on the effectiveness of the supported TMD control is that the floor inclination causes the tuned mass block to have a gravity component.From the parametric analysis in Chapter 2,it can be seen that the magnitude of the tuned mass ratio shows a positive correlation with the degree of influence of the floor inclination on the supported TMD control system.Therefore,the physical mass of the tuned mass block is reduced to attenuate the effect of the floor inclination on the supported passive tuning device control system.Under the condition of the same tuning mass ratio,the damping effect of RIDTMD is better than that of TMD,that is to say,RIDTMD is able to realize the control effect of TMD with smaller tuning mass ratio,thus realizing the lightweight control of passive tuning damping.Based on this,this paper proposes the design of a performance-based RIDTMD for lightweighting.It should be noted that the lightweight design of RIDTMD refers to the reduction of its relative to the TMD tuning mass ratio while achieving the TMD control objective.With structural displacement and structural comfort as performance objectives,respectively,the three RIDTMDs are designed for lightweighting according to the lightweighting design process.The validity and accuracy of the obtained optimal parameters of the lightweighted RIDTMDs are demonstrated by frequency-domain and time-domain analyses.The performance indexes are defined for evaluating the lightweight performance of the three RIDTMDs,and a reasonable recommendation for the selection of lightweight RIDTMDs is given by comparing the performance indexes of the three lightweight RIDTMDs.The extremely limited upper space of the towering structure not only restricts the size of the tuned mass ratio,but also makes it difficult to provide enough operating space for the supported passive tuned vibration damping device.For this reason,this paper proposes the optimized design of a limit-type RIDTMD control device based on the control objective.Depending on the type and intensity of external load excitation suffered by the towering structure,the control objectives that engineers are concerned with will also change.Under the one-in-ten-year wind load excitation,the design of the damping device is mainly aimed at controlling the comfort of the structure.Under the excitation of wind load of one in fifty years,one in one hundred years and earthquake,the design of damping device mainly aims at controlling the safety of the structure.The so-called optimized design of the limit-type RIDTMD based on the control objective refers to the multi-stage optimized design of the RIDTMD according to the different control needs of the different stages of the towering structure,so that it can accomplish the established control objective while minimizing the travel of the tuning mass block to adapt to the limited operating space of the towering structure.Since the control objective of the first stage of the RIDTMD is the comfort of the towering structure,the control parameters of the first stage of the RIDTMD are based on the criterion-based acceleration optimization parameters.The maximum travel of the tuned mass block under a one-in-ten-year wind load excitation is calculated using the extreme value distribution probability,and this travel is used as the first stage travel of the limit type RIDTMD.The operating space provided by the towering structure is used as the limit travel of the tuned mass.The second stage of the RIDTMD is designed by adding tuned damping between the first stage travel and the limit travel to minimize the travel of the tuned mass while accomplishing the control objectives of the second stage.Using the limit travel of the tuned mass block as the constraint function and the structural displacement as the objective function,an intelligent only algorithm is used to obtain the optimal tuned damping design parameters for the second stage.The effectiveness of the limit-type RIDTMD optimization design based on the control objective is verified by time-domain analysis.