Research On Wind-Induced Snowdrift Effect Of Box Girder

Wind-induced snowdrift refers to the complex movement of snow with the action of wind.The uneven distribution of snow will have an adverse impact on the bridge structure,it is possible to reduce the safety and stability of the bridge.At present,there are few studies on snowdrift of bridge,which exist lots of shortcomings.The main work and conclusions of this paper are as follows:1.The Hertz Mindlin(no slip)and Hertz Mindlin with JKR cohesion contact model in DEM(Discrete Element Method)are used to simulate the angle of repose of snow.Taking the measured results of angle of repose of snow as the target value,select reasonable parameters of snow(including the properties of snow and collision parameters).The method of collapse is used to measure angle of repose of snow of particle model(DEM).Determining the contact parameters between particles.The results show that Hertz Mindlin with JKR cohesion contact model can reflect the adhesion state between particles and improve the accuracy of CFD-DEM coupling simulation of wind-induced snowdrift.2.Based on the CFD-DEM coupling,the wind-induced snowdrift of typical step structures is numerically simulated.By selecting the determined contact parameters,the wind field and snow distribution in the numerical simulation are compared with the wind tunnel results of Tsuchiya,the results are agreed with experimental results.Then,according to the basic theory of wind-induced snowdrift,the similarity criteria that must be met in the wind tunnel test are discussed.The heavy-density quartz sand particles are selected as the material to simulate the snow particles,the relevant properties of quartz sand particles are measured,the wind-induced snowdrift wind tunnel test is carried out on the step structure,and the wind-induced snow redistribution on the low roof of the step structure in different wind speeds is studied.Finally,the results of numerical simulation,wind tunnel test and field measurement are compared,and the three agree well,which verifies the feasibility of CFD-DEM two-way coupling numerical simulation method.3.Taking four box girders of highway bridges and railway bridges with different spans as the research objects,the wind-induced snowdrift of the main girder is simulated by using CFDDEM two-way coupling method.The flow field distribution around the main girder,the characteristics and differences of wind-induced snow redistribution of the main girder and the influence of snow on the aerodynamic force of the main girder are studied in different wind angles of attack and wind speeds.The results show that under the condition of constant wind angles of attack,the flow field around the main beams of highway bridge and railway bridge is not sensitive to wind speed,and there are only local differences in some areas,which can prove that the effect of wind field on snow phase is basically the same.Ancillary structures such as protective fence,track and catenary will significantly affect the distribution of flow field on the bridge deck,resulting in uneven distribution of snow on the bridge area.The effect of wind angle of attack on the snow distribution in the bridge area is less than wind speed.Within a certain wind speed range,with the increase of horizontal inflow wind speed,the snow erosion area in the main beam bridge area of highway bridge and railway bridge will increase significantly.At the same time,the uneven distribution of snow will change the aerodynamic shape of the main beam.The average difference of resistance coefficient,lift coefficient and moment coefficient of highway bridge and railway bridge is about 28% compared with the absence of snow.Among them,the average difference of lift coefficient of main beam of small-span Highway Bridge is more than 40% compared with the absence of snow,and the average difference of lift coefficient and moment coefficient of main beam of long-span highway bridge is more than 25% compared with the absence of snow.The moment coefficient of small-span railway bridge is about 25%higher than the absence of snow,and Long-span Railway Bridge is about 40% higher than the absence of snow.