Study On The Influence Factors Of The Flutter Performance Of The Ultra-Long Span Separated Steel Box Girder

The ultra-long span bridge is an important development direction in the construction of the modern bridge over the sea and river. The 3300 meter span of the ultra-long span bridge has been designed recently. Because the ultra-long span bridge’s structure is more slender and more flexible, the damping ratio is smaller, the structure natural frequency is low, wind resistant performance has become an important control factor in design of ultra-long span bridge. The bridge girder section is closely related to the flutter performance of bridge. Therefore, studying the flutter influence factor of bridge girder section is of great significance to improve the flutter critical wind speed.Firstly, the development history of the long-span bridges at our country and abroad was reviewed. For long-span bridge vibration action under the strong wind, the necessity for research of the bridge flutter performance was emphasized. Then, the research methods of bridge flutter problem was described, the wind tunnel test and numerical simulation study on flutter analysis method has been summarized and their characteristics and application range has been indicated.Secondly, the basic knowledge of existing computational fluid dynamics was described. According to the past method for the identification of bridge flutter derivatives, the flutter derivatives of the separated box girder bridge has been identified. By comparing the flutter derivatives of the ideal flat plate from analytic expressions, the correctness of the numerical simulation method has been proved. Besides, the method was applied to solution of flutter derivatives of various aerodynamic measures of the separated box girder.Thirdly, the two-dimensional flutter analysis of two common methods of derivation and calculation principles have been introduced. According to the principle of the calculation, the two dimensional coupling flutter analysis method and the direct flutter analysis method were compiled. The flutter critical wind speed of the flat plate was calculated by using two kinds of calculation program. Compared with the flutter derivatives from the flat wind test, these two method are proved to correct. Then, two kinds of were applied to the bridge flutter analysis which the bending frequency ratio is close to 1. The calculation process was described and the advantage, disadvantage and application of the two methods have been studied.Finally, in order to study flutter performance of the rail ventilation rate, stable board, space of box girder to separated steel box girder. Then, three aerodynamic measures of nine kinds of programs that different ventilation of railings, different number of horizontal stabilizer and different space of box girder have been designed. Through the wind tunnel test, the scheme of the aerodynamic measures impact on the separated steel box girder have been investigated and the flutter optimal scheme has been achieved.