Theoretical Analysis And Experimental Study Of Single-side Pounding Tuned Mass Damper For Structural Vibration Control

Civil structures are prone to produce vibrations subjected to dynamic loadings such as strong winds and earthquakes.Large amplitude vibrations occurred on civil structures may degrade the serviceability and even endanger the structural safety.Structural vibration control is significant to ensure the serviceability of civil structures and enhance the structural safety against strongly dynamic loadings.Recently,researches on the structural vibration control attract attentions with more and more construction of low-damping civil structures.In this paper,a novel passive control device,single-side pounding tuned mass damper(SS-PTMD),is proposed to mitigate structural vibrations.The proposed SS-PTMD consists of a pounding mass,a spring and a pounding boundary covered with viscoelastic materials layer.The studies related on the modeling of the pounding force between steel and viscoelastic materials layer,the dynamic behavior of the SS-PTMD and the optimum parametric deign were conducted to evaluate the control performance of the SS-PTMD.Moreover,applications of the proposed SS-PTMD to control vortex-induced vibrations,structural seismic response and cable vibration were investigated.The works included in this paper are summarized as follows:(1)Firstly,an overview related to structural vibration control technologies was performed,especially to those control devices employing the pounding damping mechanism.Considering the drawbacks of the existing pounding tuned mass damper,a novel single-side pounding tuned mass damper(SS-PTMD)was proposed.(2)The free pounding experiments between steel and viscoelastic materials layer was conducted to study the energy dissipation and the nonlinear behavior during poundings.The elastic aftereffect phenomenon was observed from pounding experiments,and the remaining surface deformation ratio was proposed to describe the nonlinear behavior.An advanced impact force model was proposed to accurately predict the nonlinear behavior of viscoelastic materials layer during poundings.The accuracy and stability of the proposed impact force model is superior to existing models.(3)The natural frequency and the equivalent damping ratio of the SS-PTMD was derived theoretically,and the relationship between the coefficient of restitution and the equivalent damping ratio was given.A comparison of the pounding simulation method between the methods using the impact force model and the velocity exchange theory was performed.Furthermore,the effect of the gap between the pounding boundary and the mass block on the dynamic properties of the SS-PTMD was investigated.The nonlinear behavior of the SS-PTMD was studied by numerical simulations.The results indicate that the SS-PTMD has more stable dynamic properties compared to the conventional pounding tuned mass damper with double-side impact boundaries.(4)The equations of motion of a single degree of freedom(SDOF)structure with a SS-PTMD control were established.The control performance of the SS-PTMD on the suppression of the free vibration and the forced vibration was investigated through numerical simulations and experiments.The effect of the frequency tuning ratio and the restitution coefficient of the SS-PTMD on the control effectiveness were studied.Based on the H? control criterion and minimizing the maximum frequency response of the controlled structure,the optimum parametric design of the SS-PTMD was conducted,and the design formulas to obtain the optimal parameters of the SS-PTMD were summarized.With the consideration of the different control mechanism,a comprehensively comparative study between the proposed SS-PTMD and the tuned mass damper(TMD)was performed to study the control performance and the robustness against the frequency detuning.The design method of an over-damped SS-PTMD was proposed with the consideration of its unique control mechanism.Differing from the conventional viscous-damped TMD,the energy transformation and energy dissipation of the SS-PTMD is independent.Furthermore,the SS-PTMD has better performance on the control effectiveness and robustness.If the SS-PTMD suffers from severe detuning situations,designing an over-damped SS-PTMD can effectively increase its control robustness.(5)Based on the classic wake oscillator model,the coupling motion equations of a SDOF structure controlled by a SS-PTMD was established to simulate the structural response under vortex-induced vibrations,and the inaccuracy of dynamic response obtained by the approximate solution was also discussed.The identification method to obtain unknown parameters in the wake oscillator model was introduced.The control performance of the proposed SS-PTMD to the vortex-induced vibration of a bridge deck model was analyzed by the wind tunnel experiments and numerical simulation,and the effect of the mass ratio on the control effectiveness of the SS-PTMD was studied through simulations.Furthermore,the control performance of the SS-PTMD considering the changes of identified parameters in the wake oscillator model and the detuning effect were respectively discussed.The results show that the optimum parameters for the SS-PTMD,obtained by considereing a harmonic excitation applied on the controlled structure,is also effective to control vortex-induced vibrations,and the SS-PTMD is also effective to control the vortex-induced vibration in multiple lock-in regions.(6)A pendulum SS-PTMD was proposed to suppress the structural response under seismic excitations.The equations of motion of a SDOF structure and a multiple degrees of freedom(MDOF)structure controlled by a pendulum SS-PTMD were respectively established.The dynamic properties of the pendulum SS-PTMD was discussed and compared to that of the aforementioned SS-PTMD with a linear spring.Based on minimizing the root mean square(RMS)of the structural response equipped with a pendulum SS-PTMD under free vibration,the optimum parametric design was performed and the simplified design formulas for the pendulum SS-PTMD was given.The control effectiveness of the pendulum SS-PTMD for a SDOF structure under earthquakes was studied by shake table tests and numerical simulations,respectively.Moreover,the control performance of the pendulum SS-PTMD on the structural acceleration response,and the energy dissipation of the structure-pendulum SS-PTMD coupling system were respectively discussed.Finally,a 10-story frame structure was used to study the control effectiveness of the pendulum SS-PTMD on the vibration control of MDOF structures.The SS-PTMD can reduce the structural displacement and acceleration response under earthquakes,and the energy dissipation ability of the structures is greatly enhanced when the SS-PTMD is attached.(7)Baed on Dongting Lake Bridge,the cable vibration due to wind and rain as well as its Magnetorheological(MR)damper control system were introduced.The mechanical performance of used MR dampers on the system after 10 years service was studied and the reason account for the performance degradation was discussed.The concept of using the SS-PTMD for cable vibration control was proposed,and the motion equations of cable-SS-PTMD coupled system were established.The control performance of the SS-PTMD to suppress the single mode vibration and multiple modes vibration was studied.A SS-PTMD was designed and ultilized to mitigate vibrations of the A10 cable on the Dongting Lake Bridge.Numerical simulations and field experiments both reveal that the SS-PTMD can significantly increase the damping ratio of the target mode,and the damping ratios of the surrounded modes are also increased.