Research Of Flutter Stability For A Suspension Bridge In Conceptual Design

In recent years, with the rapid development of computer technology, thenumerical wind tunnel technology based on computational fluid dynamics iswidely used in hydraulic, mechanical, environmental, civil engineering andother fields. The numerical wind tunnel technology is not affected by testconditions, has a good repeatability, and can also simulate complex geometricalshapes of flow field, so it has become an important study tool at the moment. Inparticular, it provides effective technical means for the early stage of the projectin the concept design phase and development prospects are very bright. Thenumerical wind tunnel technology is used to study the flutter performance ofsuspension bridge design and the implementation effect of aerodynamic controlmeasures in the thesis, and the related design suggestions for the conceptualdesign scheme of suspension bridge are provided.In this thesis, bridge flutter characteristics of main girder sections based onthe Scanlan theory are studied. Using numerical wind tunnel method, the flowfield is meshed by ANSYS FLUENT software pretreatment ICEM CFD software,then the state of forced vibration test is achieved using the dynamic model ofgrid technology and a UDF program, the aerodynamic force time history data toidentify flutter derivatives is extracted by using the Realizable k ξmodel andPISO numerical algorithm. Compared with the theoretical solution ofTheodorsen, the effectiveness and correctness of the method is verified by usingthe above method to identify the ideal flat flutter derivatives.Using the above methods, two kinds of main girder cross sections in thetwo dimensional flow field are simulated, flutter derivatives are identified, andfour kinds of suspension bridges flutter critical wind speed are calculated underthe construction state (without railings and maintenance) and finished bridgestate (with railings and maintenance) in-5°~+5°wind attack angle. The resultsfor flutter derivatives fit well between the simulated finished bridge state andthe Humen2nd bridge wind-tunnel test results. The results show that therailings and maintaining ways reduce the bridge flutter critical wind speed, theaerodynamic performance of girders gradually becomes poor and the fluttercritical wind speed of suspension bridges are declining with the absolute valueincrease of wind attack angle, and the minimum flutter critical wind speed isunder the condition of+5°wind attack angle, the most unfavorable wind attack angle.In order to optimize the pneumatic controls, four kinds of new crosssections, the central-slotted measure, vertical stable plates, oblique stable platesand central stable plates to the central-slotted bridge section, are studied. Underthe most unfavorable wind attack angle, the four kinds of new sections with thepneumatic control measures were analyzed to make an evaluation. The central-slotted measure improves the flutter stability significantly, the locations ofstable plates have different effects on the section flutter performance. Thecontrol effect of the central stable plate is better than oblique stable plate, whilevertical stable plate will reduce flutter critical wind speed. The central-slottedmeasue with a vertical stable plate as the best flutter improved aerodynamic wayis recommended.