Research On Structural Broadband Vibration Control Method Based On Bandgap And Damping Mechanism

Train-induced vibration and noise pose new challenges to structural engineering.Different from low-order vibration of structures caused by earthquake,wind,and pedestrian forces,the frequency spectrum of environmental vibration caused by rail transit is characterized by a broader and higher frequency band.Under the excitation of track environment vibration,the axial and bending vibration of the structure and its components at 1～500Hz has "both wide-band multimodal vibration and spatial fluctuation characteristics",which causes the problems of human vibration comfort(1～80Hz)and secondary structure noise(20～500Hz).In the field of structural engineering,there is also a lack of vibration reduction control measures for such broadband(1～80Hz and 20～500Hz)excitation.In a specific range of frequency(called "band gap"),acoustic/vibration metamaterials have the characteristics that the vibration mode of any wavelength cannot be propagated.The technology based on metamaterials provides new insight into the problem with both multi-mode vibration and spatial wave characteristics.However,it is still a great challenge to effectively use the broadband vibration mitigation mechanism in finite engineering structures(different from the existing metamaterial research based on the infinite structure assumption)considering boundary conditions,damping,and oscillators’ uneven layout.Therefore,aiming at the most common flexural and axial vibration and wave in engineering,this thesis systematically studies the control mechanism,measures,performance evaluation indicators,and control methods for structural broadband vibration reduction based on band gap and damping mechanism.A new measure to control the train-induced vibration in high-rise buildings is put forward.The main contributions of this thesis include the following:1.Focusing on typical beam and plate members distributed with oscillators,the modal damping calculation theory is proposed.Modal damping can be used in designing and optimizing multi-mode or even dense-mode vibration control.2.For a composite plate with distributed oscillators,the correlation of damping and vibration reduction from a single-point excitation of the beam to a multi-point nonuniform excitation of the plate is studied using the modal damping calculation theory.A calculation formula that can accurately predict modal damping under different boundary conditions is proposed;3.A periodic parallel constrained damping beam with both band gap,and damping attenuation characteristics is proposed.The spatial attenuation effect of bending waves and the combined effect of damping and band gap is studied.4.The high-rise building is simplified as a "column+equivalent oscillators" system,and the vertical vibration mode theory and parameter analysis are applied to reveal the vertical vibration propagation law of high-rise buildings caused by subway train.5.Because the traditional vibration isolation bearing cannot be applied to high-rise buildings,this thesis proposes the concept of setting a "wave barrier layer" locally in high-rise buildings and clarifies the vertical vibration reduction mechanism of "wave barrier layer" on vertical structural members(columns,walls)and floors,which provides new insight into the vibration reduction of high-rise buildings adjacent to the railway.