Study On Wind Field Characteristics And Structural Dynamic Characteristics Of The Sea-crossing Bridge

Wind loads and wind-induced vibrations are important factors affecting the safety of structures for long-span structures such as bridges,because typhoons and monsoons are frequently.Long span structures have the characteristics of small stiffness.The bridge is a typical wind-induced sensitive system,which is easy to produce deformation and vibration under the wind load.Therefore,it is necessary to carry out analysis on the wind load determining parameters of the bridge in the coastal area,i.e.the threecomponent force coefficients.The study methods include numerical simulation and wind tunnel test.The suspension bridge area is severely affected by typhoons.At present,there is no standard code for typhoons at home and abroad.Therefore,it is necessary to conduct in-depth study on the characteristics of the wind near the ground boundary layer and its change law in coastal areas.The suspension bridge can monitor and evaluate the structural condition through the structural health monitoring system in the operation stage,and the analysis based on the structural response data can identify the dynamic characteristics of the structure modal parameters.The modal parameter identification of structure has a strong application prospect.The identified modal parameters can estimate the damage of structure and predict the response of structure.Typhoon data and structural response data carry a lot of information,and energy proportion is one of them.Typhoon energy may be absorbed by the girder under certain conditions,which will cause structural damage of the girder and change the dynamic characteristics of the structure.Therefore,it is important to study the correlation of the typhoon and the girder of the bridge by using the energy analysis method.Based on these,the main research contents of this article are as follows:(1)Considering the characteristics of lattice girders with various cross-section,an arch bridge was taken as the research object in the coastal area.Based on its structural characteristics and the influence of ancillary facilities,a three-dimensional numerical simulation model was established.The three-component force coefficient was refined by a three-dimensional numerical simulation model.The obtained three-component force coefficients are compared with the wind tunnel test results.The influence of the ancillary facilities on the three-component force coefficients and the correlation between numerical simulation error and wind vortex are discussed.(2)The health monitoring system of the suspension bridge has accumulated a large amount of measured data in the operation stage.Based on the wind speed data of a suspension bridge during the typhoon,the analysis method of wind characteristics was used to study the mean wind speed,mean wind direction,wind shear exponent,turbulence intensity,gust factor and wind speed power spectrum during typhoon Soulik and the typhoon Jongdari.On this basis,the fitting curves were drawn and the reference values of each parameter were calculated,and compared with the recommended value of the code.The analysis data provides the real value for the actual wind characteristics of the bridge site.(3)Based on the analysis of the measured data of the acceleration responses of the girder of a suspension bridge during the typhoon,the power spectrum peak method and stochastic subspace method on data-driven were introduced to identify the modal parameters of the girder.The natural frequency and damping ratio of the girder were obtained,and the structures identified by the two methods were compared with the results of the loading test to verify the effectiveness of the two methods.Considering the complexity and calculation accuracy of the two methods,the applicability,convenience and accuracy reference of power spectrum peak method and random subspace method were proposed.(4)Considering the typhoon energy and the acceleration energy of the girder,the theory of wavelet packet node analysis was introduced.Based on the measured data of acceleration responses of 10 typhoons from 2013 to 2018,the energy distribution of the typhoon and girder were plotted.According to the analysis results,it was found that the energy of the typhoon and the girder mainly distributed in the low frequency band,and the they had a strong correlation.