Nonlinear Analysis And Experimental Study Of Viscoelastic Bionic Multi-dimensional Vibration Isolation Structure Specialty: Structural Engineering

As a natural geographical disaster that accompanies the development of human society for a long time,earthquake has caused huge hidden danger for the health service of building structures.Under the action of earthquake,the excessive dynamic response of the building structure will lead to irreparable damage to the external major structure and internal precision equipment,and even cause serious collapse of the building,which will bring untold damage to human safety and social development.The vibration isolation and mitigation technology of building structure can effectively reduce the damage caused by earthquake,which has been widely used in practical engineering.However,the earthquake action usually causes multi-dimensional dynamic response to the building structure,and the traditional isolation bearings fail to meet the control needs of multidimensional isolation and mitigation performance.Therefore,based on the bionic design principle,this paper proposes a new type of viscoelastic limb-like-structure(VE-LLS)unit and a new type of viscoelastic bionic multi-dimensional vibration isolation(VBM-VI)device.The dynamic mechanical properties of the device are tested.The vibration isolation and mitigation effect of the device are studied by shaking table test.In addition,the multi-dimensional isolation bearing has complex coupling characteristics of material nonlinearity and geometric nonlinearity,which makes the dynamic analysis and calculation of the isolation and mitigation structure more difficult.The dynamic calculation and analysis of the vibration isolation system is carried out considering the coupling effect of material nonlinearity and geometric nonlinearity.The specific research work is as follows:(1)Based on the excellent vibration isolation and mitigation performance of bird legs,a viscoelastic limb-like-structure(VE-LLS)unit is proposed.A series of dynamic mechanical properties tests are carried out on VE-LLS unit.The effects of ambient temperature,excitation frequency and amplitude,and device geometric parameters on its mechanical properties and energy dissipation capacity are studied by calculating and analyzing the test results.The results show that the VE-LLS unit has excellent mechanical properties and energy dissipation capacity,which are significantly affected by ambient temperature,excitation frequency,amplitude and geometric parameters of the component.(2)The mechanical model of VE-LLS unit is established.The energy dissipation capacity of VE-LLS unit is studied,and an energy dissipation model is proposed.An energy dissipation capacity compensation strategy is proposed to improve the energy dissipation stability of VE-LLS unit under different ambient temperatures and excitation frequencies.The nonlinear static stiffness theory of VE-LLS unit is studied,and the nonlinear stiffness characteristics are deduced and theoretically studied.The results show that the proposed mechanical model and energy dissipation model can accurately describe the mechanical properties and energy dissipation capacity of VE-LLS unit.The energy dissipation compensation strategy can make the unit has stable energy dissipation capacity under different ambient temperatures and excitation frequencies.The influence law of unit parameters on its nonlinear stiffness shows significant difference.(3)By combining VE-LLS unit with viscoelastic core pad,a new viscoelastic bionic multi-dimensional vibration isolation(VBM-VI)device is proposed.The mechanical properties of VBM-VI device are tested in horizontal and vertical directions,and the mechanical properties of the device are studied.The mechanical model of the device is established,and the accuracy of the mechanical model is verified by comparing the calculation results with the test results.The results show that the proposed VBM-VI device has excellent mechanical properties and energy dissipation capacity in both vertical and horizontal directions,and the proposed mechanical model can accurately describe the mechanical properties of the device.(4)The shaking table test of structure installed the VBM-VI device is carried out to study the isolation and mitigation effect of the device under the excitation of multiple seismic waves at frequent and rare earthquake intensities.The peak acceleration of the controlled structure and the shaking table are compared and analyzed,the dynamic amplification coefficient of the controlled structure is calculated and discussed,and the isolation and mitigation efficiency of the multi-dimensional isolation and mitigation system is quantitatively studied.The results show that the VBM-VI device has good vibration isolation and mitigation performance under the action of seismic waves.(5)Based on the nonlinear vibration control theory,the nonlinear dynamic equation of the VBM-VI system is established,and the coupling nonlinear characteristic under the coupling action of geometric nonlinearity and material nonlinearity is considered.Based on the nonlinear frequency-domain analysis method and the harmonic balance method,and the nonlinear effects of ambient temperature and excitation frequency on the stiffness and damping characteristics of viscoelastic materials are considered in real time.Through parameter analysis,the nonlinear influence law of device parameters on the isolation effect of VBM-VI device is studied.The results show that the coupling nonlinear characteristics of the device have a significant impact on its vibration isolation performance.Different vibration isolation effects can be achieved by adjusting the values of the parameters of the device reasonably to meet the actual needs of different engineering.