Performance Testing Of Variable Frequency TMD And Experimental Study On Vertical Vibration Control Of Plates And Shells

Tuned mass damper(TMD)is especially effective for reducing vertical vibration of structures such as footbridges and long-span floors.The necessary condition for vibration reduction is that its frequency need to be consistent with the frequency of main structures.However,the stiffness degradation of structure happens in the process of long-term use,live load and pedestrian load will change frequently,which will make vibration frequency of structure change,so the frequency of traditional TMD is not consistent with the frequency of the structure,which causes the damping effect decreased sharply.Based on a new type of magnetorheological elastomer,a variable frequency TMD damper is developed in this paper,which can change the frequency of TMD with the demand of the main structure.The research results can form a set of research theory and integration technology of variable frequency TMD,which is of great significance for promoting the application of intelligent material structure system in civil engineering.In this paper,the development and application of magnetorheological materials,especially magnetorheological elastomers and TMD are summarized.The basic theories of magnetorheological elastomers and TMD are introduced,and the shortcomings of TMD in engineering application are pointed out.By studying the influence of variable frequency TMD structure and magnetorheological elastomer thickness on the performance of frequency conversion TMD,the variable frequency TMD magnetic circuit structure is determined,and a variable frequency TMD based on magnetorheological elastomer is designed and developed.The relationship between shear modulus of MRE and the applied current is studied,the magnetic circuit analysis results show that the shear modulus of MRE will increase with the increase in the applied current,shear modulus increment is large in the range of 0 to 1A,and it is close to the saturation value when the current is about 1.8A,In this way,the variable frequency TMD parameters including the adjustable stiffness range are determined.A structrure of variable frequency TMD and fixed beam is established and the calculation of fixed beam vertical vibration control simulation is completed,the damping effect of traditional TMD and frequency of TMD is tested,and damping effect of the different mass ratio of variable frequency TMD and traditional TMD is analysed.The results showed that when the frequency difference between main structure and TMD is bigger,the required quality of variable frequency TMD is smaller than the TMD to achieve the same damping effect,this also reflects the advantages of quality of variable frequency TMD.Finally,taking the long-span floor structure as an example,the vertical vibration control of the long-span floor structure under the action of pedestrian load is carried out by using variable frequency TMD.The results verify the feasibility of application of the TMD in practical engineering.