Study On The Prediction And Control Of Structure-Borne Noise Of Rail Transit Bridges

When a train runs across a bridge, vibration energy is transmitted from the track structure into the bridge deck and other components which act as different size of’sounding boards’. These’sounding boards’also radiate noise, namely, re-radiated noise, which results in’hot spots’in noise maps for bridge sections. In this dissertation, the prediction and control of structure-borne noise from bridge are studied based on numerical simulation and field measurement. The main contents include:(1) The achievements related to the prediction and mitigation of structure-borne noise from bridge are reviewed and summarized from three aspects experimental research, numerical analysis and noise reduction measures. The numerical methods include Finite Element Method (FEM), Boundary Element Method (BEM), Statistical Energy Analysis (SEA) and others. The noise reduction measures contain construction material, sound barrier, vibration isolation and/or reduction, viscoelastical damping material, bridge structural type, and so on.(2) A comparative analysis of the measured Sound Pressure Level (SPL) of four elevated bridges at home and abroad is done, and then, four problems on test equipment, evaluation method, Noise Source Identification (NSI) and measuring point arrangement are pointed out. Subsequently, the suitable evaluation and identification method of structure-borne noise are investigated. Based on this, the in-suit noise test on a32m simply-supported pre-stressed concrete box girder with two tracks on it has been done; the measured time-frequency characteristic and propagation law of noise are analyzed according to four types of measuring point.(3) Based on the theory of Train-Track-Bridge Coupling Vibration (TTBCV), BEM and SEA, this dissertation puts forward a novel method of calculating structure-borne noise of various rail transit bridges covering the low-and middle-frequency range. The dynamic responses of bridge and rails are identified as the boundary condition and external energy input in the BEM and SEA model, respectively. Meanwhile, the’strong-coupling’assumption is introduced to simplify the solution of Coupling Loss Factors (CLF) between subsystems in the SEA model. A computer program based on these strategies is developed on the MATLAB(?) platform, that is, the steady analysis of structure-borne noise from bridge is achieved.(4) The rationality of’strong-coupling’assumption is checked based on numerical analysis. Meanwhile, the validation of prediction model is completed by field measurement as well as the explanation of peak frequency of structure-borne noise for box girder. By numerical simulation, the former32m box girder is selected as the case study, the vibro-acoustic mechanism, frequency spectrum characteristic and spatial distribution law of structure-borne noise are investigated, respectively. After that, the influences of train speed, pier height, sound barrier and ground reflection on the overall SPL are obtained.(5) A single track32m simply-supported pre-stressed box girder is selected as the case study, the variations of material property (elastic modulus, density and damping), structural thickness (top plate, bottom plate and web plate), inclination angle of web plate and boundary condition (simply-supported and clamped) on the overall SPL of structure-borne noise are investigated. Followed that, two32m double track simply-supported pre-stressed box girder are compared related to the structure-borne noise, the cross section of the first is single box with single chamber while the other one is single box with double chamber. Similarly, the vibro-acoustic mechanism, frequency spectrum characteristic and spatial distribution law of noise SPL of a32m double line simply-supported pre-stressed concrete U-shape girder are studied.(6) A moving concentrated force-box girder-Multiple Tuned Mass Dampers (MTMDs) coupling vibration model is presented; the time-domain differential equations are derived and subsequently decoupled by Modal Superposition Method (MSM). According to the intermediate variable of Frequency Response Function (FRF), the optimization object function is constructed, which is solved by a Constrained Nonlinear Programming Model (CNPM). Based on this, the former double track32m box girder is selected as the case study, the effectiveness of MTMDs on the control of vibration and noise radiation of box girder is investigated.(7) The acoustic radiation characteristic of a simple rectangle plate is studied, whose acoustic radiation power is decoupled by Rayleigh Integral Method (RIM). Subsequently, the acoustic radiation mode of it is analyzed. After that, the general formula of acoustic radiation power, the MSM, BEM and Generalized Eigenvalue Decomposition (GED) of matrix are combined to simultaneously diagonalize the matrix of acoustic radiation impedance and mean-square vibration velocity. That is, decoupling of an arbitrary three-dimensional complex structure is realized, and the structural radiation efficiency can be gained by simple addition of eigenvalue and eigenvector. Based on this, structural acoustic radiation power is identified as the object function, and the active control strategy of using Secondary Force Source (SFS) is investigated. On the MATLAB(?) platform, the codes of decoupling of acoustic radiation power and optimal SFS of an arbitrary three-dimensional complex structure are gained. After that, the former U-shape girder is selected as the case study, and the acoustic radiation mode and active control of it are researched.