Study On The End Effect Of Typical Bridge Section Model

The section model is the most commonly used model type in the wind tunnel test of bridge.The three-dimensional flow around the end of the model is an error factor that cannot be ignored in the wind tunnel test.This paper studies the end effects of rectangular,streamline box girder and Π shaped girder according to the control means of the end effects of length width ratio and binary end plate(1)In view of streamline box girder and Π shaped girder,section models with aspect ratio of 1,2,3 and 4 are made respectively.Aerodynamic coefficients of each model are measured in wind tunnel to find out the influence of aspect ratio on aerodynamic coefficients of typical bridge section models.The aerodynamic coefficients obtained are substituted into the static wind stability and buffeting response calculation program of the whole bridge,and the minimum limit value of the length width ratio of the bridge section model in the wind tunnel test is obtained by synthesizing a series of results.(2)For the rectangular section model with aspect ratio of 10,the section model with different aspect ratio is simulated based on CFD technology,and the laws of aerodynamic spread distribution,aerodynamic coefficient and wind pressure distribution with aspect ratio are obtained.After simplification,the aerodynamic spread distribution model is obtained.Based on the spread distribution model,the table of aerodynamic coefficient with model length is presented.The accuracy of the expression is verified by the way of least square fitting.(3)The CFD numerical model of streamlined box girder section models with different aspect ratio(the aspect ratio of streamlined section model is 10,which is equivalent to the tangent angle of rectangle)is established.The laws of aerodynamic spread distribution,aerodynamic coefficient and wind pressure distribution changing with aspect ratio are obtained.The laws of rectangular and streamlined section model changing with aspect ratio are compared,and the section type is compared with the length and width of section model The influence of specific effect.(4)In the wind tunnel,the section model with end plate and without end plate are tested to check the role of end plate in the end effect control.Based on the relatively simple and convenient two-dimensional CFD,an idea of determining the reasonable end plate size of the segment model is proposed.