| The tuned mass damper(TMD)is a device of energy dissipation and vibration attenuation to achieve the goal of vibration attenuation by absorbing the vibration energy of major structure through the small mass-spring system attached to major structure,without increasing the load on the structure.It can be used permanently after installation due to its simple structure and easy installation.TMD system is a device system composed of mass block,stiffness element and damping element.When the mass of mass block is constant in TMD system,the control effect of TMD will be affected by damping ratio and frequency ratio.This paper,with the high-rise structure of actual view tower as the object of TMD vibration control,designs the TMD with two-stage variable damping eddy current and verifies the damping effect of TMD and the feasibility to install TMD onto view tower through shaking table test,with detailed jobs as follows:(1)Establish the three-dimensional finite element model.Simplify the three-dimensional finite element model through generalized flexibility method.It is can be obtained through the analysis on dynamic characteristics of simplified model and finite element model that the simplified model can reflect the dynamic characteristics of original structure well.After the simplified model and three-dimensional finite element model are respectively stimulated under the wind load in down-wind direction for 10 years,the responses on the top level of structure are basically the same.So it is very reliable to analyze wind-induced dynamic response and seismic response through simplified model.(2)Analyze the crosswind resonance of view tower as well as the wind-induced dynamic response and seismic response of simplified model.The damping effect of TMD on wind-induced dynamic response in crosswind direction is superior to that under the action of earthquake.The acceleration response on the top level of structure cannot meet the requirements when the simplified model encounters the resonance of wind load in crosswind direction once in a decade.The response of structure is reduced greatly under the control of TMD,which enhances the comfort level of view tower largely.(3)Design the scale model and the TMD with two-stage variable damping eddy current in the shaking table test program for the structure model of view tower.Firstly,determine the similarity coefficients of model structure,design the basic components of model structure and complete the scale model.Secondly,design the parameters for the TMD with two-stage variable damping eddy current,process the TMD with eddy current,test the material performance and complete the additional weight manually.Finally,select and adjust the seismic wave and propose the generation and modification of equivalent base acceleration under the wind load in crosswind direction.(4)Analyze the shaking table test results for the model structure of view tower in detail.Firstly,analyze the dynamic characteristics of model structure.There is little difference between the model result of model structure back stepped to original structure and that of original structure,so the model structure can reflect the dynamic characteristics of original structure in a better way.After the seismic fortification of seven degrees,the frequency change of model structure is little and the model structure is still in the elastic state.After the rare seismic action of seven degrees,the frequency change of model structure is larger than that after the seismic fortification of seven degrees.And at this moment,the model structure has been damaged slightly.Then,test the performance of the TMD with eddy current.It can be obtained from test results that the damping ratio of TMD caused by rail friction is 10.6%,but that of TMD with eddy current is 21%,double than that of TMD without eddy current.So the eddy current can make a great contribution to the damping ratio of TMD.Through the analysis on top-level relative displacement response,absolute acceleration root-mean-square response and relative displacement root-mean-square response in the model structure of view tower with and without TMD control,we can obtain the results that the general control effect of TMD is good.There into,the control effect is comparatively excellent on the relative displacement of structure model and the control effect of TMD on model structure response under the action of equivalent base acceleration of wind load in crosswind direction is better than that on seismic action.So it is feasible to install TMD onto view tower to control the vibration attenuation of structure. |
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