Study On Flutter Performance Of Streamlined Box Girder With Aerodynamic Stabilizer And The Mechanism Of Flutter

Since the first use of streamlined box girders in Severn Bridge in the UK,streamlined box girders with excellent flutter performance have gradually become the preferred girder type for long-span bridges.As the bridge span increases,the critical wind speed of the flutter decreases.Therefore,aerodynamic countermeasures need to be installed on the streamlined box girder to improve its flutter performance of the girder.An aerodynamic stabilizer has been widely used in practical engineering as a simple and valuable configuration.However,the current aerodynamic stabilizer design of streamlined box girder comes from experience and wind tunnel test results.There is no systematic research,and the influence of aerodynamic stabilizers on the flutter performance of streamlined box girder cannot be obtained.Meanwhile,there is also a lack of systematic research on the flutter mechanism.Therefore,three streamlined box girder sections with aspect ratios of 11,9,and 7 were selected,and different aerodynamic stabilizers were adopted.The flutter wind tunnel tests of the section model were systematically carried out.Based on perceiving the influence law of aerodynamic stabilizer,based on the coupled flutter closed-form solutions,the influence mechanism of the streamlined box girder flutter was revealed.The research results of the paper can provide a reference for the flutter design of streamlined box girders.The main research content and results of this paper are as follows:(1)Streamlined box girders section model with three aspect ratios were made for the testing.For the original section,a single aerodynamic stabilizer,two aerodynamic stabilizer combinations,and three aerodynamic stabilizer combinations,210 kinds of cases of orthogonal tests were designed and conducted.In addition,the flutter critical wind speeds of different streamlined box girder models under different aerodynamic combinations were obtained through the section model wind tunnel tests.(2)The test results show that when the upper central stabilizer with an aspect ratio of 11 is adopted for the upper central stabilizer of 0.37 H,the flutter critical wind speed is the largest,which is 40.8% higher than that of the original section.When there are two kinds of stabilizer combinations,section C with an aspect ratio of 7 adopts the upper central stabilizer of 0.19 H and the lower central stabilizer of 0.22 H,and the flutter critical wind speed is the largest,which is 86.6% higher than the original section.When the three types of stabilizers work together,the C section with a width-to-height ratio of 7 adopts the upper central stabilizer of0.19 H,the lower central stabilizer of 0.22 H and the horizontal stabilizer of 0.07 B,and the flutter critical wind speed is the largest,which is 92.9% higher than the original section.(3)Four representative aerodynamic combination sections were selected,and the flutter derivatives of the streamlined box girder under each aerodynamic combination were obtained based on the sub-state forced vibration method.The variation law of the four key flutter derivatives was analyzed.(4)Based on the coupled flutter closed-form solutions,combined with the flutter derivatives,the variation curves of aerodynamic damping with the converted wind speed under different aerodynamic combinations were analyzed.The effects of different aerodynamic combinations on coupled negative damping and non-coupled positive damping were compared.The influence mechanism of different aerodynamic stabilizer measures on flutter was revealed.